AGRICULTURAL INVESTIGATIONS BERT 1 684 UNIV. OF CAL, EKPT, STA. LIB, AGRIC, DEPT, '/itb the compliments of HOUGHTON FARM. r ^ 1 * i ON AGRICULTURAL INVESTIGATION- BEING A LECTURE DELIVERED OCTOBER 27, 1884, AT RUTGERS COLLEGE, NEW BRUNSWICK, N.J UNDER THE AUSPICES OF THE NEW JERSEY AGRICULTURAL EXPERIMENT STATION, THE STATE BOARD OF AGRICULTURE, AND THE STATE AGRICULTURAL COLLEGE; JOHN HENRY GILBERT, M.A., LL.D., F.R.S. OF ROTHAMSTED, ENGLAND. AND SIBTHORPIAN PROFESSOR OF RURAL ECONOMY IN THE UNIVERSITY OF OXFORD. ,\ PUBLISHED BY THE SOCIETY FOR THE PROMOTION OF AGRICULTURAL SCIENCE. 1885. ON AGRICULTURAL INVESTIGATION; BEING A LECTURE DELIVERED OCTOBER 27, 1884, RUTGERS COLLEGE, NEW BRUNSWICK, N. J UNDER THE AUSPICES OF THE NEW JERSEY AGRICULTURAL EXPERIMENT STATION, THE STATE BOARD OF AGRICULTURE, AND THE STATE AGRICULTURAL COLLEGE; JOHN HENRY GILBERT, M.A., LL.D., F.R.S OF ROTHAMSTED, ENGLAND. AND S1BTHORPIAN PROFESSOR OF RURAL ECONOMY IN THE UNIVERSITY OF OXFORD. PUBLISHED BY THE SOCIETY FOR THE PROMOTION OF AGRICULTURAL SCIENCE. 1885. NOTE ON DR. GILBERT S LECTURE. It has been announced that Sir John Bennet Lawes, in arranging for the perpetual maintenance of the great work of Rothamsted, makes provision for a representative of that establishment to visit- America every other year and lecture at appropriate places. Dr. Gilbert was in the United States in 1882, and when it was known that he was to come again in 1884, efforts were made to have him attend the fifth annual meeting of the Society for the Promotion of Agricultural Science. As his various engagements unfortunately prevented his being in Philadelphia at the time desired, arrangements were there made to secure lectures from him at other places. He accordingly visited Lansing, Michigan, and New Brunswick, New Jersey, for the purpose, and found appreciative audiences at both places. The lecture at Rutgers College was under the joint auspices of the New Jersey Agricultural Experiment Station, State Agricultural College, and State Board of Agriculture. , The Society for the Promotion of Agricultural Science, having intended this lecture to be a part of its proceedings at Philadelphia, have asked and obtained per- mission to first publish the same in this pamphlet. For this purpose the text has been carefully revised and the tables verified by Dr. Gilbert. This kind attention is gratefully acknowledged by THE EXECUTIVE COMMITTEE. v : >': LECTURE ON AGRICULTURAL INVESTIGATIONS. J. H. GILBERT. Mr. President, Professors and Students of Jtutgers College, and Ladies and Gentlemen : I ESTEEM it a high honor and a great responsibility to be called upon to address you on the present occasion; an honor because, perhaps, I am not assuming too much in supposing that I owe the invi- tation to do so to the fact that the joint labors of Sir John Bennet Lawes and myself, in the furtherance of agricultural progress, which have now extended over a period of more than forty-one years, are held in some appreciation in this country; and a responsibility, because I know that I have before me representatives of the best agricultural science in the Eastern States. On hearing from Sir John Lawes, before leaving home, that I might probably be asked to lecture at some Agricultural Institutions in Amer- ica, I at once decided that it would be inappropriate for me to attempt to discuss, in any detail, American agricultural practices or experiments ; that in these matters I should be a learner rather than a teacher ; and that it would be more suitable for me to give some account of the results obtained at Rothamsted, leaving my audience to decide for themselves, in great measure, how far the facts and the conclusions were applicable to American conditions. In Germany and France very much good work has been done, both in the laboratory and feeding-shed, during the last thirty years or more ; but in Germany, at any rate, we have it on the authority of Prof. Maercker of Halle, one of their leading agricultural chemists, that sys- tematic field experiments are almost abandoned in that country. In 1880, Prof. Maercker stated that belief in their value was greatly dimin- ished, and that by some they were declared to be of no value. It was objected that the chemists of the Agricultural Stations have neither the means nor the technical knowledge necessary for carrying out such experiments successfully ; that neither the amount of land nor the funds at their disposal were such as to admit of any safe deductions for appli- cation in practical agriculture from the results ; and that purely physio- logical problems could be better investigated in the laboratory or in the greenhouse. He remarked that, owing to the errors necessarily incident to field experiments conducted by those not acquainted with practical agriculture, the confidence of the practical farmer in the results has been shaken. Indeed, owing to the difficulties and the cost of such inquiries, 320923 if conducted v iiv a truly 'scientific manner, so as to be applicable for the solution of questions of fundamental and general interest, Prof. Msercker concluded that the only field experiments which it was practicable to carry out in Germany were such as should be conducted by the practical farmer himself, to test the applicability to practice, of results and conclu- sions otherwise arrived at ; and that, to insure that even such experi- ments should not be misleading, similar ones should be conducted on different descriptions of soil, and for several years in succession. That the great cost of scientifically conducted field experiments should have prevented the more extended prosecution of them, is perhaps not surprising when I tell you that the Rothamsted field experiments, inde- pendently of all the laboratory investigations connected with them, cost considerably more than ^1000 annually ; whilst those which have been undertaken by the Duke of Bedford at Woburn for the past seven years, on behalf of the Royal Agricultural Society of England, and which are under the direction of Dr. Vcelcker, cost not much less than this. At various institutions in America, and preeminently at the New Jersey Agricultural Experiment Station, very much good work is being done of the character prosecuted with so much success in Germany, and recommended by Prof. Msercker to be still further followed up ; and whilst such work should be continued and extended, surely investiga- tions of a more permanent value, and of more general application, should not be neglected. Nor can it be supposed that in so wealthy a country as America, where there is so much munificence and public spirit displayed in all matters of progress, the cost of scientifically con- ducted agricultural experiments will be any obstacle. This brings me to the special subject-matter of my lecture, which is to illustrate the value of long continued and carefully conducted experiments, by reference to the results of one series of such experiments conducted at Rothamsted, namely, those on the growth of wheat for more than forty years in succession on the same land ^vithout manure, with farm- yard manure, and with a great variety of chemical manures. But, before entering upon the details of this subject, it will be well to give some account of the scope and plan of the whole investigation, of which these special results only form a part. At Rothamsted, no questions of mere local interest or economy are undertaken. The object is rather to investigate the principles under- lying fundamental practices ; and whilst results obtained in one locality, on one description of soil, and with one character of climate, require to be carefully studied before conclusions applicable to other localities and to other countries can be drawn, yet it is believed that the results which have been obtained are of very general and wide application. The general scope and plan of the field experiments has been to grow some of the most important crops of rotation, each separately, year after year, for many years in succession on the same land, without ma- nure, with farm-yard manure, and with a great variety of chemical ma- nures, the same description of manure being, as a rule, applied year after year on the same plot. Experiments with different manures on the mixed herbage of permanent grass-land, on the effects of fallow, and on an actual course of rotation, without manure, and with different manures, have likewise been made. Field experiments have thus been conducted for the periods, and over the areas, indicated in the following table: ROTHAMSTED FIELD EXPERIMENTS. CROPS. DURATION YEARS. AREA, ACRES. PLOTS. Wheat (various manures) 41 13 37 Wheat alternated with fallow AVheat (varieties) 33 15 1 4-8 2 About 20 Barley (various manures) Oats (, various manures) Beans (various manures) 33 10 1 32 2 ! 29 6 10 Beans (various manures) 27 3 i 5 Beans alternated with wheat 28 4 10 Clover (various manures) 30 5 3 18 "Various Leguminous Plants 7 3 17 Turnips ^ various manures) Su^ar Beet (various manures) 28 5 8 8 40 41 Mangel Wurzel (various manures) 9 8 41 Total Boot Crops 42 Potatoes (various manures) 9 2 10 Rotation (various manures) 37 2V 12 Permanent Grass (various manures) . ... 29 7 22 ( x ) Including 1 year fallow. ( 2 ) 1 " wheat laiiow. wheat and 5 years fallow, i-; 4 years fallow. (4) " 2 " " ( 5 ) Clover, 12 times sown, 8 yielding crops, but 4 of them very small, 1 year wheat, 5 years barley, 12 years fallow. ( 6 ) Including barley without manure 3 years (llth, 12th and 13th sea- sons.) Samples of all the experimental crops are brought to the laboratory. Weighed portions of each are partially dried and preserved for future reference or analysis. Duplicate weighed portions of each are dried at 100 C., the dry matter determined, and then burnt to ash. The quantities of ash are determined and recorded, the ashes themselves being pre- served for reference or analysis. In a large proportion of the samples the total nitrogen is determined, and in some the amount existing as albuminoids, amides, and nitric acid. In selected cases, illustrating the influence of season, manures, exhaustion, etc., complete ash-analyses have been made, numbering in all more than 700. Also in selected cases, illustrating the influence of season and manuring, quantities of the experimentally grown wheat-grain have been sent to the mill, and the pro- portion and composition of the different mill-products has been deter- mined. In the sugar-beet, mangel-wurzel, turnips, and potatoes, the sugar in the juice has, in many cases, been determined, by polariscope, or by copper, or both. In the case of the experiments on the mixed herbage of permanent grass-land, besides the samples taken for the determination of the chemical composition (dry matter, ash, nitrogen, woody fiber, fatty matter, and composition of ash), carefully averaged samples have frequently been taken for the determination of the botan- ical composition. Samples of the soils of most of the experimental plots have been taken from time to time, generally to the depth of nine, eighteen, and twenty-seven inches, and sometimes even to four times this depth. In this way more than fifteen hundred samples have been taken, submitted to partial mechanical separation, and portions of the sifted soil have been carefully prepared and preserved for analysis. In a large proportion of the samples the loss on drying at different temperatures, and at igni- tion, has been determined. In most, the nitrogen determinable by burn- ing with soda-lime has been estimated. In many, the carbon, and in some the nitrogen, as nitric acid, and the chlorine, have been determined. Almost from the commencement of the experiments the rain-fall has been measured ; for more than thirty years in a gauge of one-thousandth of an acre area, as well as in an ordinary small funnel-gauge of five inches diameter. From time to time the nitrogen as ammonia (and sometimes as nitric acid) has been determined in the rain-waters, also chlorine in many samples. Three drain-gauges, for the determination of the quantity and compo- sition of the water percolating, respectively through twenty inches, forty inches, and sixty inches depth of soil (with its subsoil in natural state of consolidation), have also been constructed. Each of the differently manured plots of the permanent experimental wheat-field having a separate pipe-drain, the drainage waters have been, and are frequently, connected and analyzed. For several years in succession experiments were made to determine the amount of water given off by plants during their growth. In this way various plants, including representatives of the gramineous, the leguminous, and other families, have been experimented upon ; also ever- green and deciduous trees. Experiments upon the feeding of animals were commenced in 1847, and have been continued at intervals up to the present time. The following points have been investigated : 1. The amount of food, and its several constituents, consumed in re- lation to a given live-weight of animal within a given time. 2. The amount of food, and of its several constituents, consumed to produce a given amount of increase in live-weight. 3. The proportion, and relative development, of the different organs or parts of different animals. 4. The proximate and ultimate composition of the animals, in different conditions as to age and fatness, and the probable composition of their increase in live-weight during the fattening process. 5. The composition of the solid and liquid excreta (the manure) in relation to that of the food consumed. 6. The loss or expenditure of constituents by respiration and the cuta- neous exhalations that is, in the mere sustenance of the living meat- and-manure-making machine. Several hundred animals oxen, sheep, and pigs have been sub- mitted to experiment. The amount, and the relative development, of the different organs and parts were determined in two calves, two heifers, fourteen bullocks, one lamb, two hundred and forty-nine sheep, and fifty-nine pigs. The percentages of water, mineral matter, fat, and nitrog- enous substances were determined in certain separated parts, and in TABLE I. Wheat grown for forty years in succession on the same land, Broadbalk Field, Rothdmsted. Results showing the effects of exJiaustion, and of manure-residue. Quantities per acre. Produce Dressed Grain in bushels. Mineral Manure " alone blue; Ammonium Salts alone (86 Ibs. Nitro- gen) yellow; Min. & Amm. Salts, Mixed Min.Manr Am. Salts. 172 Ibs. N. 13 years, 1852-'64. Unman'd since. 14 Tons Farm Yard Manure, every year. Mixed Mineral Manure alone, blue; Ammonium Salts alone=86 Ibs. Nitro- gen, yellow; alternately. Without! Mixed Manure Mineral green; CTnmanured white Bushels 20% 32 27 X 29% S* Bushels. Busnela. Harvests. 1844 1845 1846 1847 1848 1849 1850 1851 8 yrs. '44-'51 1852 1853 1854 1855 1868 1869 1870 1871 1872 1873 1874 1875 1876 1877 1878 1879 1880 1881 1HS-J 4 yrs. '52-'55 4 yrs. '56-'59 4 yrs. '60-'63 4 yrs. '64-'67 4 yrs. '68-'71 4 yrs. '72-'75 4 yrs. '76-'79 4 yrs. '80-'83 30% 38 37% 34^ 38% 31% 23 34^ 8 yrs. '52-'59 8 yrs. '60-'67 8 yrs. '68-'75 8 yrs. '76-'83 34% 35% 35% 28% 16 yrs. '52-'67 16yrs.'68-'83 35% 31% 32yrs.'52-'83 33% 40yrs.'44-'83 32% (1) Average of 5 years, 18601864, inclusive. (3) Average of 5 years, 18601864, inclusive. (5) Average of 13 years, 18521864, inclusive. (2) Average of 3 years. 1865 1867, inclusive. (4) Average of 11 years, 18651875, inclusive. (6) Average of 19 years, 1865 1883, inclusive. 7 the entire bodies, of ten animals, namely, one calf, two oxen, one lamb, four sheep, and two pigs. Complete analyses of the ashes, respectively, of the entire carcasses, of the mixed internal and other " offal " parts, and of the entire bodies, of each of these ten animals, have also been made. From the data provided as just described, as to the chemical compo- sition of the different descriptions of animal, in different conditions as to age and fatness, the composition of the increase whilst fattening, and the relation of the constituents stored up in increase to those consumed in food, have been estimated. To ascertain the composition of the ma- nure in relation to that of the food consumed, oxen, sheep, and pigs have been experimented upon. The loss or expenditure of constitu- ents, by respiration and the cutaneous exhalations, has not been deter- mined directly, but only by difference, that is, by calculation, founded on the amounts of dry matter, ash, nitrogen, etc., in the food, and in the (increase) fceces, and urine. Independently of the points here enumerated, the results obtained have supplied data for the consideration of the following questions : 1. The characteristic demands of the animal body, for nitrogenous or non-nitrogenous constituents of food, in the exercise of muscular power. 2. The sources in the food of the fat produced in the animal body. 3. The comparative characters of animal and vegetable food in human dietaries. Having given a brief outline of the scope and plan of the investiga- tions that have been in progress at Rothamsted for so many years, I propose to draw my illustrations as to the character and significance of the results obtained, mainly from those relating to the growth of wheat for more than forty years in succession on the same land : 1. Without manure. 2. With farm-yard manure. 3. With a great variety of chemical manures, both individual con- stituents and mixtures. Table I. gives the number of bushels of dressed grain per acre without manure, and with farm-yard manure, in each of the forty years, 1844 to 1883 inclusive; and on some of the artificially manured plots, mainly selected to illustrate the effects of exhaustion and of manure-residue. In most cases in this table, and in all cases in the subsequent tables, the results obtained on the artificially manured plots are only given for the last thirty-two of the forty years, as during the first eight years the ma- nures were not the same year after year on the same plot as they were subsequently. FIRST. WITHOUT MANURE. After a five-course rotation since manuring (turnips, barley, peas, wheat, oats), the first experimental wheat crop was harvested in 1844. The highest yield of the series was 23^ bushels in 1845, and the lowest 8 was 4^ bushels in 1879. Other yields have been 21^ bushels in 1854, . 20 in 1857, only 5^ in 1853, and only 8-9 bushels in 1867, 1875, 1876, and 1877. In the lower division of the table (I.) the average produce is given for each four years, each eight years, each sixteen years, and for the thirty- two years from 1852 to 1883 inclusive; also for the whole period of forty years. Without manure, the average annual produce over the four-year periods was 14^, 17^, 14^6, 12^, 13^, 10^,8^, and 12^ bushels; over the eight-year periods, 16}^, 13^, 12^, and io}4 ', over the sixteen-year periods, 14^5 and u^j ; over the thirty-two years, 13^, and over the forty years, 14 bushels. With such wide variations due to season, it is very difficult to estimate the rate of decline due to exhaus- tion. Excluding the very bad seasons, the decline due to gradual ex- haustion is reckoned at from one-fourth to one-third of a bushel per acre per annum. It is estimated that over a period of thirty years the unmanured plot yielded an average of 18.6 Ibs. of nitrogen per acre per annum in the crop, and lost a minimum of 10.3 Ibs. in drainage, in all 28.9 Ibs.; whilst on the mixed mineral manure plot (5), it is estimated that the crop re- moved an average of 20.3 Ibs. of nitrogen, and that at least 12 Ibs. were lost by drainage, or in total 32.3 Ibs. Further it is estimated that the soils lost to the depth of twenty-seven inches about two-thirds of these amounts; leaving, say, 10 Ibs. more or less to be otherwise accounted for. Of this, the rain, etc., would supply 5 Ibs., or perhaps rather more, and the seed about 2 Ibs., so that there is but little to be provided from all other sources. Lastly, as at the commencement the soil was, agri- culturally speaking, exhausted, the nitrogen supplied by it would be largely due to old accumulations. SECOND. FARM-YARD MANURE EVERY YEAR. In the application of farm-yard manure every constituent is supplied in excess. The highest yields of the series of years were 44 bushels in 1863,41^ m 1868,41^ in 1857, and 41^6 in 1854. The lowest yields were 16 bushels in 1879, 19^ in 1853, 20^ in 1844, 23^ in 1876, and 24^ in 1877. The average produce per acre per annum over each of the five eight- year periods was, 28, 34^, 35^, 35^, and 28^ bushels. Excluding the first eight years, and several of the recent very bad seasons, the average produce is about 35 bushels per acre per annum. On the farm-yard manure plot, the first nine inches of soil show a great accumulation ; it is nearly twice as rich in nitrogen as any other plot, yet this richness is not proof against bad seasons ; nor are the highest amounts of produce in the field obtained on this plot. Thus, without manure, or with mineral manure alone, there is a grad- ual decline in yield, and with this a marked reduction in the nitrogen of the soil. With farm-yard manure, on the other hand, there is great ac- cumulation, and yet not the fullest crops, a large proportion of the con- stituents becoming very slowly available. The next question is, which constituents of farm-yard manure are tht most effective for wheat in this agriculturally exhausted rather heavy soil, with a raw clay subsoil. The first illustrations on this point will be drawn from Table II. TABLE II. Wheat grown for forty years in succession on the same land, Broadbalk Field, Eothamsted; commencing 1844. Results showing the effects of different manures for 32 years, 1852-83 in- clusive. Quantities per acre. Produce DRESSED GRAIN IN BUSHELS. Superphosphate, and Sulphates Potash, Soda, and Magnesia. Alone. A Amm.-salts AAmm.-salts =43 Ibs. =86 Ibs. Nitrogen. Nitrogen. * Amm. -salts =129 Ibs. Nitrogen. * Sodium Ni- trate =86 Ibs. Nitrogen. Sodium Ni- trate alone. =86 Ibs. Nitrogen. Plots. 5 6 7 8 9a 9b Harvests. 1852 1853 1854 1855 Bushels. 16f 10J 24| 18J Bushels. Bushels. 201 26f 18i 23f 34 45* 28 33~ Bushels. 27i 23* 48| 31 Bushels. 25 ll{ 38| Bushels. 24i 25| 1856 1857 1858 1859 19* 232 181 20f 27} 35 28^ 29^ 36! 44 39) 34 39 48 41 34 32| 43| 157^ 30 26 3& 23 24 1860 1861 1862 1863 15i 15* 17! 19 \ 22 271 28V 39| 27; 35 35i 53: 31 35 1 39 55 32f 33| 43* 55| 19 13 1 25 T ft > 1864 1865 1866 1867 16 7 14] 13 9; 31^ 25 20 16 , 45^ 40; 2ft 2-2. 49i 43 32 30 51i 44 32 29, i 33^ 29^ 30^ 22^ 1868 1869 1870 1871 t^ 17 X r-H TH r-l r-H TH 28| 21 30} 17 391 28j 40l 223 ' 46 34 1 45 47] 39 45 34i 40 J 35i 38 30 - 27i 24? 26^ 17| 1872 1873 1874 is?:, CO CO tO tO 204 15] 25] 29| 22 39 25j 35f 27i 40 30 2i 211 21* 16* 1876 1877 1878 1879 10^ 11 14; 5| 15 14| '2\ m 23 19i 31 16; 29 24| 38 20 33j 40 37 22 13 27f 23f 4| 1880 1881 1882 1883 171 12i 12 15^ 27 21f 231 27| 344 26 35; 36, - 35* 30; 37 41^ 34 35J 31^ 43 10 i 221 AVERAGES. 4 ys. '52-55 4 ys. '56-59 4 ys. '60-63 4 ys. '64-67 4 ys. '68-71 4 ys. '72-75 4 ys. '76-79 4 ys. '80-83 174 20} 17* 13| 16 12 10f 14| 251 30* 29f 23J 24f 19| 151 32 38 38 34J 325 29! 22^ 33; i 1 32J 41 40i 39 38^ 33 28; 36; I \ 26J 36 41 39^ tt 36 33 36 t 24 1 27 25; 29 23 20! 17 19 ] ! | 8 ys. '52-59 8 ys. '60-67 8 ys. '68-75 8 ys. '76-83 19 15J 14 12| 271 261 22 2pj 35J 36; 31 28 t 36J 39i 36 323 311 40; 39 34| [ 26J 27^ 22 18; 16 ys. '52-67 , 16 vs. '68-83| 171 13k 27 211 35i 29J r 38} 34i r 35| 36^ L - 26i 20; 32 ys. '52-83J 151 24| 32^ 363 363 23J ! Excess of ave- rage crop over Plot 5 in bush. Hi 171 21 21 83 IA 10 Taking the average for each eight or sixteen years of the thirty-two, it is seen that in every case, even with full mineral as well as nitrogenous manure, there is more or less decline in the later periods including so many bad seasons; excepting on ga, where the nitrate of soda is always applied in the spring. The low results or great decline, on gb, where the nitrate is used alone, show the want of minerals. The average of the thirty-two years of mineral manure alone shows an increase of only 2*^ bushels over that of the unmanured plot, though during the preceding eight years it had been manured, whilst the unma- nured plot had already grown eight unmanured wheat crops. The ad- dition to the mineral manure of the first 43 Ibs. of nitrogen (plot 6) gives an average annual increase of 8^ bushels, the second 43 Ibs. (plot 7) an increase of 8^, and the third 43 Ibs. only 3^ bushels increase. This result affords an illustration of the inapplicability of conclusions from manure experiments, when the condition of the land is too high already, or when an excess of manure is applied. A given quantity of nitrogen in the form of nitrate, yielded more produce than an equal quantity in the form of ammonia. The nitrate, being always applied in the spring, was not subject to winter drainage. It is, however, very soluble, and becomes rapidly distributed and available ; but it is, at the same time, very subject to drainage after sowing, if heavy rains follow. Prior to 1878, the ammonium-salts were applied in the autumn, and a great loss of nitrogen by winter drainage, chiefly as nitrates, was proved. To the loss of nitrogen by drainage reference will be made further on. Thus, minerals not being deficient, the increase was in proportion to the available nitrogen, when it was not applied in excess. It will be of interest here to call attention to the actual amounts of carbon assimilated per acre per annum in wheat, and in barley, under different conditions of manuring ; also to the increased amount assim- ilated under the influence of nitrogenous manures. In Table III. are shown the estimated amounts of carbon, yielded per acre per annum, in wheat over twenty years, and in barley over twenty years ; each with the complex mineral manure alone, and each with the same mineral manure and given quantities of nitrogen in addition, supplied as ammonium-salts, or as nitrate. The gain of carbon by the use of the nitrogenous manure is also given. TABLE III. Yield and gain of Carbon per acre per annum in crops at Rothamsted. Average Carbon per acre per annum. Wheat 20 years 1852,71. ACTUAL LBS. LBS. GAIN. Complex Mineral Mai do do do do do do lure. 988 1590 2222 2500 and 43 Ibs. N. as Ammonia and 86 Ibs. N. as Ammonia and 86 Ibs. N. as Nitrate. . . 602 1234 1512 Barley 20 years 1852,71. Complex Mineral Manure, 1138 do do and 43 Ibs. N. as Ammonia 2088 950 It is quite evident that in the case of these gramineous crops, wheat and barley, which contain a comparatively low percentage of nitrogen, and assimilate a comparatively small amount of it over a given area, there was a greatly increased amount of carbon assimilated by the addi- tion of nitrogenous manure alone. In the case of the wheat, there was much more effect from a given amount of nitrogen supplied as nitrate, which was always applied in the spring, than from an equal quantity as ammonium-salts, which were applied in the autumn and the nitrogen of which was subject to winter drainage. There is also more effect from ammonium-salts applied to barley than to wheat ; the application having been made for the former in the spring and for the latter in the autumn. It should be observed that there was this greatly increased assimilation of carbon in the wheat and in the barley for more than twenty years, with- out the addition of any carbon to the soil. It is, indeed, certain that, in the existing condition of our old arable soils, the increased growth of our staple starch-yielding grains is greatly dependent on a supply of nitrogen within the "soil. It'is equally certain that the increased pro- duction of sugar in the gramineous sugar-cane, in the tropics, is likewise greatly dependent on the supply of nitrogen within the soil. It will further be of interest to call attention to the connection between nitrogen accumulation, chlorophyl formation, and carbon assimilation. TABLE IV. Relation of Carbon assimilation to Nitrogen accumulation, and to Chlo- rophyl formed. 1 Nitrogen percentage in Dry Matter.* Relative Amount of Chloro- phyl. Carbon per acre PIT annum Ibs. Actual Difference. HAY. Graminese, 1.900 Leguminosw, 2.478 0.77 2.40 WHEAT. Plot 10a, (1.227) 2.00 Plot 7, (0.566) 1.00 1398 2222 -824 BARLEY. Plot la, (1.474) 3.20 Plot 4a, (0.792) 1.46 1403 2088 -685 * The figures given in parenthesis are on the substance partially dried, but not fully dried at 100 C. It should be observed that the amounts of chlorophyl recorded are as stated, relative, and not actual ; and the figures show the relative amounts for the individual members of each pair of experiments, and not the comparative amounts as between one set of experiments and another. It should further be stated that the chlorophyl determinations were kindly made by Dr. W. J. Russell, F. R. S., of London, in specimens collected at Rothamsted, whilst the wheat and barley were still green, and actively growing. It will be seen, in the first place, that the separated leguminous herbage of hay contained a much higher percentage of nitrogen in its dry matter than the separated gramineous herbage ; and that, with the much higher percentage of nitrogen in the leguminous herbage, there was also a much higher proportion of chlorophyl. 12 Next, it is to be observed that the wheat plant on plot loa, manured with ammonium-salts alone, shows a much higher percentage of nitrogen than that of plot 7, with the same amount of ammonium-salts, but with mineral manure in addition. The high proportion of chlorophyl again goes with the high nitrogen percentage; but the last column of the table shows that on plot loa, with ammonium-salts without mineral manure, with the high percentage of nitrogen and high proportion of chlorophyl in the green produce, there was eventually a very much less assimilation of carbon. The result is exactly similar in the case of the barley ; plot i a being manured with ammonium-salts alone, and plot 42. with the same ammonium-salts and mineral manure in addition. It is evident that the chlorophyl formation has a close connection with the amount of nitrogen assimilated; but that the carbon assimila- tion is not in proportion to the chlorophyl formed, if there is not a sufficiency of the necessary mineral constituents available. No doubt there had been as much or more of both nitrogen assimilated, and chlorophyl formed, over a given area, where the mineral as well as the nitrogenous manure had been applied ; the lower proportion of both in the dry matter being due to the greater assimilation of carbon, and consequent greater formation of non-nitrogenous substance. The next point to consider is, what is the effect of the unrecovered amount of nitrogen on succeeding crops. This is illustrated Dy the results in the colored columns of Table I. ,In the table mineral manure is indicated by blue, nitrogen as ammonium-salts by yellow, and a mixture of the two by green. Plot 5 has been manured continuously for thirty- two years with mineral manure alone; whilst plots 17 and 18 each received mineral manure, and a quantity of ammonium-salts containing 86 Ibs. of nitrogen alternately. Thus we are able, for every year, to compare a plot manured with minerals, succeeding a previous applica- tion of ammonium-salts, with a plot receiving mineral manure alone yearly. It is seen that, in every case, the application of nitrogen has given a greatly increased yield, frequently doubling that of the plot with mineral manure alone. Again, in every case, the yield of the suc- ceeding year, when the mineral manure was applied, was reduced ap- proximately to that of the plot continuously treated with minerals alone. A glance down the alternately blue and yellow columns of plots 1 7 and 1 8, and a comparison with the blue column of plot 5, will bring these results strikingly to view. A comparison of the averages of the periods of four, eight, sixteen, and thirty-two years of this treatment clearly shows the essential identity of the results of the continuous and the alternate treatment with mineral manures. The averages for the thirty- two years show an increase in the yield of the mineral-manure years after ammonia, over the yield of plot 5, of only ^ of a bushel per acre per annum in a crop of between fifteen and sixteen bushels. The non- effect, or the absence, of residual nitrogen applied in the form of ammo- nium-salts, is evident. In other words, nitrogen as ammonium-salts applied in any one year is practically exhausted that year, in the crop or otherwise, leaving practically none for subsequent action. Again, plot 16, for thirteen years, from 1852 to 1864 inclusive, re- ceived annually mixed mineral manure and ammonium-salts, containing a double quantity (172 Ibs.) of nitrogen ; and since that time, for nineteen years (1864-1883), it has been left unmanured. During the thirteen years of heavy manuring there was a large yield, in two cases exceeding fifty bushels, with an average for the thirteen years of 39^ bushels. The first three years during which no manure was applied, the average yield was only 21^4 bushels, a decrease of nearly one-half, followed in the succeeding periods of four years each by average yields of 17^, 12, 9^5, and 13^ bushels; against, for the corresponding periods on plot 3, continuously without manure, 8^4, 13^, 10^, and 12^ bushels. Or, taking the average of the nineteen years of yield without manure on plot 1 6, we have 14^5 bushels, against, over the same years, 13^ bushels, on plot 5, with mineral manures only, since 1852, and nfo bushels on plot 3, unmanured since 1839. It is fair to presume, moreover, that some of the greater yield of plot 16, from 1864-1883, over that of plot 3. is due to the residue of the mixed mineral manure, which, as will be seen further on, has some effect on succeeding crops. If, as the above results have demonstrated, there is practically no residue from previous application of ammonium-salts, the question arises, What becomes of the nitrogen of the manure not taken up by the crop ? This point is illustrated by the results given in Table V. The plots there tabulated all received the same amount of nitrogen in manure, with differing mineral manures, and they are given in the order of their aver- age annual increased yield of nitrogen in the crops over plot 5, with mineral manure alone. The first column shows the estimated average annual increased yield of nitrogen per acre in the crops ; the second, the estimated annual loss of nitrogen as nitric acid by drainage ; the third, the estimated annual excess of nitrogen in the surface-soil over that on plot 5 with the mineral manure alone; and the last column shows the relation which that excess in the soil bears to 100 increased yield of nitrogen in the crops. The plots were manured as follows: Plot 10 Amm. -salts = 86 Ibs. N. " ii Amm. -salts _ 86 Ibs. N., and superphosphate. " 12 Amm. -salts 86 Ibs. N., superphosphate and soda. " 13 Amm.-salts = 86 Ibs. N., superphosphate and potash. " 14 Amm. -salts = 86 Ibs. N., superphosphate and magnesia. " 7 Amm.-salts = 86 Ibs. N., and mixed mineral manure. " 9 Nitrate of soda = 86 Ibs. N., and mixed mineral manure. TABLE V. BROADBALK EXPERIMENTAL WHEAT-FIELD. Estimated Nitrogen per acre per annum. Plots. In Crops over Plot 5. Lost by Drain- age over Plot 5. In surface soil 9 inches deep over Plot 5. Excess in surface soil to 100 increase in Crop. Ibs. Ibs. Ibs. Ibs. 10 12.4 31 2 4.8 38.7 11 17.7 28.5 11.6 65.5 12 22.2 24.5 14.6 65 8 13 23.4 25.6 17.8 76.1 14 24 1 27.5 15 5 64.3 7 25.9 19.0 19.3 74 5 9 26.5 23.7 18.5 71.2 14 It is seen that the increased yield of nitrogen in the crops varied ex- ceedingly with the same amount supplied in manure, according to the condition as to supply of mineral constituents. Plot 10, with the ammo- nium-salts alone, gives the smallest increased yield of nitrogen in the crop ; and plots 7 and 9, with the most complete mineral manure, each more than twice as much; the other plots giving intermediate amounts. The order of the estimated loss of nitrogen by drainage is almost the converse of that of the increased yield in the crops. Plot 10, which gives the least increased yield in the crop, shows the greatest loss by drainage; and plots 7 and 9, which yield the greatest increase in the crop, show the least loss by drainage. The excess in the soils (over plot 5) is obviously much more in the order of the increased yield in the crops. Plot 10, with the least in the increase of crop and the most in the drainage, shows the least excess in the soil; whilst plots 7 and 9, with the greatest increased yield in. the crop, and the least loss by drainage, show the greatest excess in the soil. It is clear, therefore, that whilst the excess in the soil has no direct relation to the amount supplied in the manure, it has a very obvious relation to the increased yield in the crop ; in other words, to the amount of growth. The last column of the table brings this out more clearly. Excepting in the case of plot 10, with the ammonium-salts alone, there is a general uniformity in the proportion of the excess in the soil over plot 5 to the increased yield in the crop over plot 5 ; and the variations, such as they are, have an obvious connection with the conditions of growth. Thus plots n, 12, and 14, all with a deficient supply of potash, show approximately equal proportions retained in the soil for 100 of in- crease in the crop. Plots 13, 7, and 9, again, all with liberal supplies of potash, show higher, but approximately equal, proportions retained in the surface-soil for TOO of increased yield in the crop. Upon the whole, it is obvious that the relative excess of nitrogen in the soils of the different plots is little, if at all, due to the direct retention by the soil of the nitrogen of the manure, but it is almost exclusively de- pendent on the difference in amount of the residue of the crops of the stubble and roots, and perhaps of weeds. This leads to the consideration of the actual differences in the crop with equal nitrogen supply and different mineral supply. This is illus- trated by the results in Table VI., which shows the effects of mineral manures alone, of ammonium-salts alone, and of ammonium-salts with different mineral manures. TABLE VI. Wheat grown for forty years in succession on the same land. Broadbalk Field, Rothamsted. Results showing the effects of Mineral Manures alone, and when used in addition to Ammonium-Salts. Quantities per acre. Produce : Dressed Gi*ain in bushels. Mixed Mineral Manure Alone. 400 Ibs. Ammonium-Salts = 86 Lbs. Nitrogen per acre per annum. Alone, Alone, 1852 and 1852 and since. ! And since, j Prev'sly And Super- Previo'sly Min.Man. And Su- Super- phosphate Min.Man. 1844, '48 perphos- phosphate and 1844. j and '50. phate. and Sulphate Am.-Salt> Am. -Su its Sulphate of 1845-51. 1845/7, '8, of Soda. Potash. '9 and '.'.I. And Super- phosphate and Sulphate of Magnesia. And Super- phosph'te and Sulphates of Potash, Soda and Magnesia. Plot No Plot 5 Plot lOa Plot lOb Plot 11 Plot 12 Plot l:i Plot 14 Plot 7 Harvests. 8 yrs. '44/51 Bushels. 29 Bushels. Bushels. Bushels. Bushels, i Bushels. Bushels. 2! 24% 27% -27', Bushels. 29.%f 1852 1854 1855 1857 1858 I S.V.I 10% 10 34% 20 22% I'' 1 , 39% H 23% 18% 43% 21% a*X 22% 45% 31% 24 23 -It': 30% 22% 44% 31% 34% 43% 38% 34% 26% 23% 45% 33 23% 18% 24% -'.:... 22% 19 27% 34 % 27% 25% 31 '4 39% 32 27% 33% 43% 37% 34% 31% 43% 37% 34% 36% 44% 39% 34% I860 1861 1862 1869 1865 1866 1867 1869 1870 1871 1873 1874 1875 15% 15% 17% 14% 13* 9% 15% 12% g* 24% 43% 22% 24% 26% 45% 27% 32% 33% 54 26% 34% 32% 27 * 33% 31 %, 54 27% 35 35% ,53% _>r> ' , 18 K :r, - , 80% 28% :{.;>, * 22% 44% 34% 28% 24', 4:* '. 37% 24% 23% 41% 8* 22% 45% 40 % 29% __23* 17% 15% 18% 24% -'I ', 10% T.'-K 25% 12% 10 18% 20% 14% Sg 39% 27% 35% 21% 39% 27% 37 30% 41% 27% 35% 24% 39% 28% 40% 22% 12% 13 9% 19* g 29!* 22% 39% 25% 29% 23% 37% 27% 30% 21 ':: 36% 26^ 29% 22 39% 25% 1876 1877 1878 1879 10% 11% 14% 5% ns 14% 29% 4% 14% 17% 29% 11% 19% 17% 14 29% 23% 34% 30% 25% 18 X 29% 16 22% 18% 32% 16% 23% 19% 31% 16 X isso 1881 1882 1883 17% 12% 1-2 >, 15% 10% 18> 4 ' 23% 17% 13% 19\ _.,;, ; 18% 25% 21% 30% 26% 33 28 '4 32% 34% 31 27% 34% 33% 34% 26% 35% 36% 4 yrs. '52/55 4 yrs. '56/59 4 yrs. '60/63 4 yrs. '64/67 4 yrs. '68/71 4 yrs. '72/70 4 yrs. '76/79 1 yrs. '80/83 17 20% 17% 13% 16 12 10% 14% 23% 22% 25% It* 18% 15 'i 17% 26% 28% 2.V., 25% 20 20% 16% 19% 26% 32% 29% 28.% 23 24% $* 31 Ji 37% 37 33 30% 29 \i 20 29% 80* 36% 36% 32% 33% 29% 22 X 31% 30% 37% 36% 32% 32% 29% 22% 31% 32% 38% 38 34% 33% 29% 22% 33% 8 yrs. '52/59 8 yrs. '60/67 8 yrs. '68/75 8 yrs. '76/83 19 14 22% 24 19 16% 27% 27'.! 20% 18% 29% 29% 23% 86 30 24% ^ ^ S y 35% 36% 31 28 16 yrs. '52/67 16 yrs. '68/83 13% 23% 17% 27% 29% 22% 34% 27% 34 2'J', 34% 28% 35% 29% 32 yrs. '52/83 15>4 20% 23* 26% 31 31% 31% 32% 5 lOa lOb 11 12 13 14 7 i6 For the thirty-two years, 1852 to 1883 inclusive, each of the eight differently manured plots received the same manure each year. I will only call special attention to the average yields over periods of six- teen and thirty-two years. Plot 5, treated with mineral manure only, gave, during the first sixteen years, an average yearly yield of 17^ bushels per acre, during the second sixteen years 13^ bushels, and during the whole period of thirty-two years 15^ bushels. Plot loa, treated with ammonium-salts only, gave, during the first sixteen years, an average yearly yield of 23^/6 bushels per acre, during the second sixteen years 17^ bushels, and during the thirty-two years an average of 20^ bushels. Thus, ammonium-salts alone produced much more than mineral manure alone. On plot lob, previous to 1852, in the years 1844, 1848, and 1850, mineral manures had been applied, in the other years previous to 1852 (excepting in 1846, when it was unmanured), and subse- quently, ammonium-salts only. The effect of the residue of the pre- viously applied mineral manures is apparent on comparison with the yields on loa. On plot lob we find, during the first period of sixteen years, an average yearly yield of 27^ bushels per acre, against 23^ bushels on loa; during the second period of sixteen years 19^3 bushels, against 17^ on ica; and during the thirty-two years, an average yearly yield of 23 1^ bushels, against only 20^ on loa. Plot n, with superphosphate but no potash, in addition to the ammonium-salts, gave, during the first sixteen years, an average yearly yield of 293/3 bushels per acre, during the second sixteen years 22^ bushels, and during the thirty-two years 26^ bushels. On plot 12, in addition to the ammonium-salts, superphosphate and sulphate of soda were applied ; but potash had been applied prior to 1852. The first sixteen years produced an average yearly yield of 34^ bushels per acre, the second sixteen years of 27^ bushels, and the whole thirty-two years of 31 bushels. On plot 13, the ammonium-salts, superphosphate, and sulphate of potash were applied, and the average annual produce was, over the first sixteen years 34 bushels, over the second sixteen years 29^, and over the thirty-two years 31^3 bushels. On. plot 14, besides the ammonium-salts and superphosphate, sulphate of magnesia was applied, and some potash had been applied prior to 1852. The average annual produce was, over the first sixteen years 34^ bushels, over the second sixteen years 28^ bushels, and over the thirty-two years 3 1 ^ bushels. On plot 7, in addition to the ammonium-salts, superphosphate and the sulphates of potash, soda and magnesia, were applied, and gave, during the first sixteen years, an average yearly yield of 35^ bushels per acre, during the second sixteen years of 29^ bushels, and during the whole thirty-two years of 32^ bushels. Thus, not only the effect upon the yield of wheat of a direct supply, but of a residue from long previous applications of potash, is very notice- able. This is rendered more obvious by reference to the following table (VII.), in which the pounds per acre of potash and phosphoric acid removed during two periods of ten years each, in the total produce, and in the grain alone, of the plots last referred to, and some others are given. TABLE VII. Potash and Phosphoric Acid in Grain, and in Total Produce. Ten years, 1852-'61, and ten years, 1862-71. PER ACRE IN POUNDS. POTASH. PHOSPHORIC ACID. 1852-'61. 1862-'71. 1852-'61. 1862-'71. TOTAL GRAIN TOTAL GRAIN TOTAL GRAIN TOTAL GRAIN PRODUCE. PRODUCE. PRODUCE. PRODUCE. 2 52.6 11.8 53.5 12.4 26.5 19.6 27.3 20.1 3 19.0 5.5 15.3 4.9 10.8 8.2 9.7 7.5 5 26.6 6.6 21.1 5.7 14.7 10.5 12.3 8.8 lOa 27.2 7.1 23.1 7.7 13.0 9.6 13.4 10.4 lOh 33.3 8.5 25.0 87 16.0 12.2 14 8 12.0 11 30.9 9.3 26 8.8 19.8 14.9 18.0 13.6 12 45.4 11.4 37.8 11.4 23.2 17 7 21 8 17.0 13 53.2 11.3 55.2 12.2 22.9 17 7 23.3 18.2 14 49.8 11.3 39.1 11.6 22.9 17.9 22.4 17.6 7 56.0 11.9 53.0 12.3 23.8 18.4 23.4 18 5 I will illustrate this point by referring only to the potash. Plots 3, loa, lob, and n show a deficiency of potash in both grain and total prod- uce compared with the amounts in the produce of plots 2, 12, 13, 14 and 7, on all of which there was a sufficiency, or more or less excess, of potash available. On comparison of these results with the manuring of the plots, we find that in every case the increase of potash in the total crop depends either on a direct annual potash supply, or on a residue from previous applications. The first ten years shows more potash in the total produce with the direct supply (13 and 7) than with the residue (12 and 14); but the amount in the grain is essentially the same in each case. In the second ten years there is a greater difference in the amounts of potash in the total produce between the plots having the direct and those having only the residual supply; whilst there is scarcely any difference in the amounts in the grain, but such as it is, it is in accordance with the conditions of supply. Hence it is evident that whilst the plant in its vegetative stages assimilates according to the available supply, it may be in excess of actual need, if there is no deficiency, the composition of the final product the seed is essentially the same. We have thus traced the effects of exhaustion, of full manuring, and of nitrogenous and non-nitrogenous manures on one particular soil. It has been seen how very different is the effect of one and the same manuring in different seasons, but the real extent of this variation is more clearly brought out in Table VIII., which shows the best, the worst, and the average produce, over a period of thirty-two years, under very opposite conditions as to manuring. i8 TABLE VIII. Wheat year after year on the same land. Broadbalk Field, Eothamsted. Produce of the best season, 1863 ; the worst season, 1879 ; and average of 32 years, 1852-1883. Plot No. Description of Manures Quantities per acre. Dressed Grain per acre Bushels. Best Season 18(53 Worst Season 1879 Diff. Average 32 yrs. 1852-'83 3 2 5 6 7 9 8 17* 44 19% 39% 53% 55% 55% 4% 16 5% 10% 16^ 22 12* 28 14 29% 37% 33% 35^ 13H 33% 15% 24% 32% 36% 36% Farm-yard Manure Mixed Min. Man. and 200 Ibs. Amm.-Salts = 431 bs. Nit. Mixed Min. Man. and 400 Ibs. Amm.-Salts = 861bs.Nit. Mixed Min. Man. and 550 Ibs. Nitra. Soda = 86 Ibs. Nit. Mixed Min. Man. and 600 Ibs. Amm. Salts=129 Ibs. Nit. We will confine our attention to the amount of dressed grain per acre in bushels. The difference in yield of the various plots in the best and worst of the thirty-two seasons is very marked. The unmanured, the mineral manured, and the heavily nitrogeneous manured plots, all suf- fered severely. In most cases the difference approaches, and in two cases (Plots 6 and 7 mixed mineral manure, together with 200 and 400 pounds of ammonium-salts, respectively furnishing 43 and 86 pounds of nitrogen) it actually exceeds the average produce of the plots. From these facts we see how easy it is to form wrong conclusions as to the effects of different manures, if experiments are conducted in only one season or in only a few seasons, and if the characters of the seasons are not studied. Not only season, but soil and locality must exercise an influence. The Rothamsted results are obtained on one description of soil, and in one locality only. Reference to the following table (IX.) shows the results obtained in experiments conducted at Rothamsted during the same eight years, but in two fields; at the same place in one field for thirty- two years; at Woburn, for seven years; at Holkham, Norfolk, for three years; and at Rodmersham, Kent, for four years. Thus, the experi- ments were made on very various soils, under various conditions from previous treatment, and in various seasons, yet the general characters of the results are accordant. TABLE IX. Results of Experiments on the growth of Wheat by different Manures, on different Soils, in different Localities, and in different Seasons. DKESSED GRAIN PER ACRE BUSHELS. AVERAGE ANNUAL RESULTS. MANURES. QUANTITIES PER ACRE. Rothamsted. Woburn, Beds, 7 years. Holkham, Rodmers- Norfolk, ham, Kent 3 years. 4 years. 8 years 1856-'63. 32 years 1852-'83. Broadbalk Hoos Broadbalk 1877-'83. 1852-'54. 1856-'59. Field. Field. Field. I Unmanured 16 15 18K 15% 18 25% Mixed Mineral Mamire, alone 19 16% 16% 16% 19* 28% Amm.-Salts, alone =86 Ibs. N. 23% 26% 20% 23% 1) 27% 31% Mixed Mineral Manure, and ) Ammonium-Salts =86 Ibs.N. ) 38% 37% 32% 37% | 32% 33% (1) By Ammonium-Salts = only 43 Ibs. N. Not only is there general accordance in the character of the results in different localities, when the averages of a number of years are taken, but the non-effect of the residue from previous application of ammonium- salts is as marked in the sandy soil at Woburn as in the very different soil at Rothamsted, Reference to Table X. will illustrate this. Stack- yard field. Woburn, received mineral manure, and ammonium-salts=:86 Ibs. nitrogen, for five successive years. The field was then divided, one portion receiving the same manure as before, and the other the mixed mineral manure, but no nitrogen. In the next year, 1883, the portion which had received nitrogen in the previous year received mineral ma- nures only, and conversely the other portion, which had received mineral manure only in 1882, received both mineral manure and ammonium- salts. It is seen that in each year, 1882 and 1883, the portion which received the nitrogenous manure yielded large crops (43^ and 45^ bushels) ; whereas, the portion on which mineral manures alone suc- ceeded ammonium-salts and large crops, yielded very small crops 131^ and 171^ bushels, respectively, against 14^ and 17^ bushels on the plot where the same mineral manures were used year after year. It is thus seen that there was no available and effective residue where the ammonium-salts had previously been applied. It may be stated, how- ever, that in 1884 there was notable effect from unexhausted residue of nitrogenous manure ; the explanation probably being that there had been very little rain, and consequently very little loss by drainage during the winter of 1883-4. TABLE X. Wheat grown year after year on the same land. Stackyard Field, Woburn. Harvests. Dressed Grain. Bueihels. 1877 1878 1879 g* 28^ 1881 1882 1883 43% (1) 13^ 1 (2) 43^ (2) 45% (1) 17* (1) Mixed Mineral Manure alone. (2) Mix. Min. Man. and Ammonium-Salts = 86 Ibs. N. Having illustrated the soil conditions necessary for the growth of wheat, it will be well to call attention to one practical application of these long-continued field experiments. For thirty-two years (1852-83) an estimate has been made of the average produce of wheat per acre in the United Kingdom, based upon the yield at Rothamsted on the un- manured, the farm-yard manured, and three of the artificially manured plots taken as one. From this the total yield of the country has been calculated ; to this the imports have been added, and the quantity re- quired for seed deducted, the final figure showing the total amount available for consumption, and from this the consumption per head of the population has been reckoned. It may be said at once that these results proved to be very near the truth. But the point of interest to a wheat-growing and wheat-exporting country like America is, the evi- dence which the results afford as to the constantly increasing require- ments of a largely importing country like Great Britain. 20 The following table (XI.) shows that during the thirty-two years, 1852-3, to 1883-4 inclusive, the area under wheat in the United King- dom has been reduced by about one-third. The average yield per acre is estimated at 28 bushels; but owing to recent bad seasons, the average for the whole period of thirty-two years was only 27 bushels, that for the first sixteen years having been 28^, but that for the second sixteen years only 25^. Thus there has not only been a reduction in area under cultivation, but in yield per acre, also; this, however, is probably temporary, whilst the reduction in area will doubtless continue. TABLE XI. Particulars of Home Produce, Imports, and Consumption of Wheat, in the United Kingdom 32 years, 1852-3 to 1883-4. Harvest years, Sept. 1 to Aug. 31. Estimated Home Produce. Available for consumption. Available for Con- sumption per head. Area under Crop. Aver'g yield per Acre. Total Home Produce. Homepro-l duce less 2 , 1 4 bush's Imports per acre less for seed. < Exports. Total. From Home Pro- duce. From Im- ports. Total. 1852-3 1853-4 1854-5 1855-6 Acres. .058.731 .013.963 .036.969 .076.447 Bushl. Quarters. 22% 11.574.982 20% 10.466.473 34% 17.563.140 27% 13.922.801 Quarters. Quarters. Quarters. 1U. 433. 464 5.902.00016.335.464 9.337.546 6.092.00015.429.546 16.427.742 2.983.00019.410.742 12. 776.300! 3.265.00016.041.300 Bush. 3.03 2.70 4.73 3.65 Bush. 1.71 1.76 0.85 0.93 Bush. 4.74 4.46 5.58 4.58 1856-7 1857-8 1858-9 1859-60 .213.651 .185.974 4.131.822 4.019.725 27 114.192.543 33% Il7.321.221 31^ 16.3U9.949 26tf J13.135.124 13.007.453 4.112.58417.120.037 16.143.915) 5.795.68721.939.602 15.147.874 4.555.67019.703.544 12.004.575 4.516.33216.520.907 3.70 4.56 4.24 3.34 1.16 1.63 1.28 1.25 4.86 6.19 5.52 4.59 1860-1 1861-2 1862-3 1863-4 3.992.657 3.898.177 3.823.947 3.698.629 22% 11.078.948 25 J 12.271.546 29^ 13.957.554 38% 17.922.048 9 . 956 . 01210 . 023 . 968 19 . 979 . 980 11.175.183 9.099.45520.274.638 12.882.069 9.205.08622.087.155 16.881.807 6.991.27023.873.077 2.75 3.06 3.51 4.57 2.77 2.49 2.51 1.89 5.52 5.55 6.02 6.46 1864-5 1865-6 1866-7 1867-8 3.685.493 3.646.691 3.649.584 3.628.910 35 % 30% 25 % 21 16.216.328 13.975.936 11.485.091 9.566.522 15.179.783 5.500.70520.680.488 12.950.305 7.313.02620.263.331 10.458.645 7.633.03318.091.678 8.545.890 9.015.54317.561.433 4.08 3.47 2.78 2.25 1.48 1.95 2.02 2.38 5.56 5.42 4.80 4.63 1868-9 1869-70 1870-1 1871-2 3.937.275 3.976.147 3.761.457 3.818.848 34 27 30 24 16.733.419 13.419.496 14.105.464 11.456.544 15.626.060 7.719.30423.345.364 12.301.205 9.921.52622.222.731 13.047.554 8.008.83921.056.393 10.382.493 9.316.60019.699.093 4.09 3.20 3.33 2.62 2.02 2.58 2.05 2.35 6.11 5.78 5.38 4.97 1872-3 1873-4 1874-5 1875-6 3.827.146 3.658.815 3.821.655 3.503.709 24 MX 29^ 22% 11.481.438 10.290.417 13.972.926 10.018.418 10. 405. 053J12. 291. 463 22. 696. 516 9 . 261 . 375 11 . 301 . 316 20 . 562 . 691 12 . 898 . 085 11 . 705 . 255 24 . 603 . 340 9.033.00013.860.07922.893.079 2.60 2.29 3.16 2.19 3.07 2.80 2.87 3.36 5.67 5.09 6.03 5.55 1876-7 1877-8 1878-9 1879-80 3.114.555 3.311.859 3.372.590 3.047.752 25 26% 30 15% 9.732.984 10.970.533 12.647.213 5.905.020 8.857.01512.107.29420.964.309 10.039.07314.408.62824.447.701 11.698.67214.145.64925.844.321 5 . 047 . 84016 . 409 . 933 21 . 457 . 773 2.13 2.38 2.75 1.17 2.91 3.42 3.32 3.82 5.04 5.80 6.07 4.99 1880-1 1881-2 1882-3 1883-4 3.057.784 2.960.066 3.157.924 2.707.949 24% 24 25% 28 9.364.464 8.880.198 10.115.225 9.477.822 8 . 504 . 4621 16 . 182 . 210 24 . 686 . 672 8.047.67917.200.10825.247.787 9.227.059J19.982.16229.209.221 8 . 616 . 211 15 . 815 . 878 24 . 432 . 089 1.95 1.83 2.08 1.92 3.72 3.91 4.50 3.53 5.67 5.74 6.58 5.45 4 yrs.'52-'56 4 yrs.'56-'60 4 yrs.'60-'64 4 yrs.'64-'68 4 yrs.'68-'72 4 yrs.'72-'76 4 yrs.'76-'80 4 yrs.'80-'84 4.046.528 4.137.793 3.853.352 3.652.670 3.873.432 3.702.831 3.211.689 2.970.931 26% il3.381.849 29% 15.239.709 28% 13.807.524 28 12.810.969 28% |13.928. 731 24% 11.440.800 24 )i 9.813.938 25% 9.459.427 12.243.763 4.560.50016.804.263 14.075.954j 4.745.06818.821.022 12.723.768 8.829.94521.553.713 11.783.656 7.365.57719.149.233 12.839.328 8.741.56721.580.895 10 . 399 . 378 12 . 289 . 528 22 . 688 . 906 8 . 910 . 650 14 . 267 . 876 23 . 178 . 526 8 . 598 . 85317 . 295 . 090,25 . 893 . 943 3.53 3.96 3.47 3.14 3.31 2.56 2.11 1.95 1.31 1.33 2.42 1.96 2.25 3.02 3.37 3.86 4. si 5.29 5.89 5.10 5.56 5.58 5.48 5.81 8 yrs.'52-'60 8 yrs.'60-'68 8 yrs.'68-'76 8 yrs.'76-'84 4.092.160 3.753.011 3.788.131 3.091.310 28 14.310.779 28% 13.309.247 26% 12.684.765 24% 9.636.682 13.159.859 4.652.78417.812.643 12.253.712! 8.097.76120.351.473 11.619.35310.515.54822.134.901 8 . 754 . 75115 . 781 . 483 ( 24 . 536 . 234 3.74 3.30 2.94 2.03 1.32 2.19 2.63 3.64 5.06 5.49 5.57 5.67 16 yrs.'52-'68 16 yrs.'68-'84 3.922.586 3.439.721 283 4 ' 13.810.013 25% 11.160.724 12 . 706 . 785! 6 . 375 . 273'19 . J)82 . 058 10.187.05213.148.51523.335.567 3.53 2.48 1.75 3.14 5.28 5.62 32 yrs.'52-'84 3.681.153 27 112.485.369 11.446.9191 9.761.894121.208.813 3.00 2.45 5.45 21 The great increase of population which has taken place within the period covered by the table has, of course, necessitated greatly increased consumption, and the" comparison of the home production and the for- eign importation, for successive periods, becomes of much interest. The table shows that the average annual consumption over the four succes- sive periods of eight years each, increase as follows : 1852-3 to 1859-60, Annual Consumption, 17,812,643 quarters. 1860-1 to 1867-8, " 20,351,473 " 1868-9 to 1875-6, " " 22,134,901 " 1875-6 to 1883-4, 24,536,234 These amounts were supplied from home produce and importation as follows: HOME PRODUCTION. IMPORTATION. 1852-3 to 1859-60, 13,159,859 quarters. 4,652,784 quarters. 1860-1 to 1867-8, 12,253,712 " 8,097,761 " 1868-9 to l8 75~ 6 > n 6 i9>353 " lo^S'S^ " 1875-6 to 1883-4, 8,754,751 15,781,483 Thus, over the first eight years, only one-fourth of the wheat consumed was obtained from foreign sources, whilst over the last eight years, nearly two-thirds of the entire consumption were imported. It is probable that the home produce will still decline, consequent chiefly on reduction of area under cultivation ; whilst with increase of population, imports must increase, and doubtless our supplies will be largely drawn from this continent. It has been stated that, excluding recent bad seasons, the average yield of wheat per acre of the old arable soils of Great Britain, is twenty- eight bushels. Comparing this yield with that of the United States, as shown in the above table, we find, on the authority of the U. S. Census Bureau, that the general average of localities and years is 11.9 bushels per acre ; a yield which is not equal to that of the continuously unma- nured plot at Rothamsted, and which is considerably less than half the average yield of Great Britain under ordinary cultivation. This may be partly due to a shorter period of growth, and to rapid maturing, or in some localities to deficiency of rain ; but it is probably largely also due to want of sufficient labor to clean the land, and to consequent luxuri- ance of weeds. Referring to the table, we find the general averages of the different sections of the States ranging from 15.1 bushels per acre in New England, to 7.3 bushels in the South Atlantic and Eastern Gulf States. Even the North-west and Minnesota, including much prairie land, give very meager average produce for such rich soil. So long as wheat is grown on such lands under the conditions frequent, and indeed almost inevitable, in the case of new settlement, that is, growing it year after year, with deficient cultivation, luxuriance of weeds, and the burning of the straw, only low yields per acre can be expected. The result is due to the fact that, under such conditions, fertility is cheap and labor dear. But with increased density of population, more mixed agriculture must 22 be adopted. Stock must be kept, the farm kept freer from weeds, the straw used instead of being burnt, and the manure from it, and from the consumed food, returned to the land. Then, and not till then, will the fertility of the rich prairie soils be conserved, and not wasted, as is too often the case under the necessities of the first breaking up, and the sparse settlement, of the country. That your rich prairie soils can, and should, yield more produce than they do, is clear from the high yields obtained occasionally, under favorable conditions of cultivation. TABLE XII Average yield per acre of Wheat and Indian Corn in the United States. (From Signal Service Reports.) Six years 1875-1880. WHEAT BUSHELS. 1875 1876 1877 1878 1879 1880 Gl.Av. New England, 16.1 10.6 7.5 9.0 14.8 9.5 13.7 7.5 17.0 11.0 13.9 12.3 6.8 6.7 11.5 10.5 10.2 9.5 8.5 13.0 16.8 13.2 9.0 7.2 11.1 12.8 16.1 14.8 18.5 9.5 15.3 14.0 6.5 7.1 13.2 13.0 15.2 12.2 12.0 17.0 15.0 13.4 8.0 8.1 7.7 16.3 15.8 13.1 12.3 14.0 13.3 14.! 5 6.2 5.6 7.7 14.1 13.5 12.5 13.2 16.0 15.1 13.0 7.3 7.3 11.0 12.7 U.I 11.6 13.6 13.4 Middle States South Atlantic States East Gulf States West Gulf States Upper Lake Region, North West Minnesota California Average, 11.7 10.3 12.9 12.6 12.4 11.7 11.9 INDIAN COEN BUSHELS. New England, 34.0 35.8 35.9 36.5 32.2 32.9 34 6 Middle States 32.2 29.2 28.7 28.7 29.4 32.9 30.2 South Atlantic States 12.0 11.5 11.3 11.4 10.7 10.2 11.2 East Gulf States 15.0 13 3 132 12 1 14 3 134 13 6 West Gulf States 21.4 23.2 22.6 24.2 15.9 24.0 21.9 Tennessee and Ohio Valley, 32.1 31.4 29.4 29.2 31.9 29.7 30.6 Upper Lake Region 27.0 31.6 23.3 37.4 38.1 36.5 32.3 North West 35.7 28 7 31 2 31 1 36 2 30 8 32 3 Minnesota 29.2 25.4 29.0 38.1 35.0 35.0 32.0 California 363 33 30 34 5 280 32 32 3 Average, 27.5 26.3 25.5 28.3 27.2 27.7 27.1 Turning to Indian Corn, Table XII. shows that the yield of that cereal is very much higher than that of wheat ; and the yield of nitrogen per acre in those corn crops would doubtless be much greater than in the wheat crops of the same localities. This is probably in part due to the high condition of the soil under which the crop is generally grown, corn generally following clover in the rotation. It is, however, doubtless in part due to the growth of corn extending much further into the late summer and autumn, the period during which nitrification is the most active in the soil, and when therefore the supply of nitrates to the plant will be greater under the same conditions of soil than in the case of wheat. This would be a very interesting subject for investigation, in the field and in the laboratory, tracing the nitrogen at various periods in the soil, in the plant, and in the drainage waters. The following table (XIII.) gives estimates of the yield of various crops on some Manitoba prairie soils : 2 3 TABLE XIII. Estimates of the yield of various Crops in Manitoba. Summary of Statistical Eeturns seven years, 1876-1882. Quantities in bushels per acre. 1876 1877 1878 1879 1880 1881 1882 GEN'L AVER. Wheat, Barley, Oats, Bye, Peas, Potato* s. 32 42 51 32 229 27 41 60 30 32 304 26 36 60 30 34 308 27 38 58 40 32 302 29 41 58 40 38 318 30 40 59 35 38 320 32 37 51 278 29 39 57 35 34 294 The above estimates are founded on the reports of numerous farmers, and it is seen that the average yield of wheat for seven years (1876- 1882) is assumed to be twenty-nine bushels. This is, however, doubtless too high, even for exclusively virgin prairie soils, under the condition of cultivation incident to new settlement ; and the result is probably accounted for by the fact that the records come chiefly from the more intelligent and better farmers. From returns since supplied to me from the Department of Agriculture at Ottawa, the average produce of wheat in Manitoba was, in 1880, 20.1 bushels, and in 1882, 24.0 bushels, instead of 29 and 32 bushels as above; whilst the average produce in 1883 is estimated at 21.8 bushels. In connection with this subject of the average yield of wheat of differ- ent countries, it will be of interest to contrast the condition of soils of very different history, as to their percentage of nitrogen, and, so far as we are able, of carbon also. Table XIV. (see next page) shows the characters in these respects of exhausted, arable soils, of newly laid down pasture, and of old pasture soils, at Rothamsted; of some other old arable soils; of some Illinois and Manitoba prairie soils; and lastly, of some very rich Russian soils. From these results there can be no doubt that a characteristic of a rich virgin soil, or of a permanent 'pasture surface-soil, is a relatively high percentage of nitrogen and of carbon, and a high relation of carbon to ni- trogen. On the other hand, a soil that has long been under arable culture is much poorer in these respects ; whilst an arable soil under conditions of known agricultural exhaustion shows a very low percentage of nitro- gen and of carbon, and a low relation of carbon to nitrogen. Finally, it has been maintained by some that a soil is a laboratory, and not a mine. But not only the facts ascertained in our own and in other investigations, but the history of agriculture throughout the world, so far as we know it, clearly show that a fertile soil is one which has accumulated within it the residue of ages of previous vegetation, and that it becomes infertile as this residue is exhausted ; and enormous as are the accumulations in the prairie lands of the American continent, it is still desirable to postpone, rather than to accelerate, the time of their exhaustion. TABLE XIV. Nitrogen and Carbon in various soils. Date of Soil Sampling. (1) In Dry Sifted Soil. Authority. Nitrogen. Carbon. Carbon to 1 Nitrogen. ROTHAMSTED ARABLE AND GRASS SOILS. Roots, 1843-'52 ; Barley, 1853-'5 ; > Roots, 1856-'69 ; Mineral Manures. 5 Wheat, 1843-'4, and each year since ; / Mineral Manures Barley, 1852, and each year since ; } Mineral Manures <, Arable laid down to grass (ten > acres), Spring, 1879 \ Arable laid down to grass (Barn- > field), Spring, 1874 \ Arable laid down to grass (Apple- ? tree field), Spring, 1863 J April, 1870 Per cent. 0.0934 0.1119 0.1012 0.1202 0.1124 0.1235 0.1509 0.1740 0.2057 0.1943 0.2466 Per cent. 1.039 1.079 Per cent. 9.3 10.7 Rothamsted. H October, 1865 October, 1881 . . March, 1868 March, 1882 February, 1882.. February, 1882.. November, 1881 . 1.154 2.412 2.403 3.377 10.3 11.7 12.4 13.7 Arable laid down to grass (Dr. Gil- ? To bert's meadow), Spring, 1858 5 January, 1879 . . . Arable laid down to grass (High- ) L - , field), Spring (?), 1838 .......$ September, 1878. Very old grass land (The Park) Feb. & Mch., 1876 VARIOUS ARABLE SOILS IN GREAT BRITAIN. Mr. Prout's Farm ; Broadfield ) surface $ Mr. Prout's Farm; Blackacre > 170 0.107 Voelcker. Mr. Prout's Farm; Whitemoor > surface 5 0.171 Wheat Soil Midlothian . . Eastlothian 0.22 0.13 Anderson. Perthshire 21 (t " Berwickshire 14 tt Red Sandstone Soil England 0.18 .... Voelcker. UNITED STATES AND CANADIAN P RAIRIE SOILS. Illinois, U. S., No. 1... 30 " " No 2 26 .... " " No. 3. 33 l( " " No. 4 34 tt Portage la Prairie, Manitoba sur- > face 5 0.247 Rothamsted. Saskatchewan district, N. W. Terri- > tory surface 5 Forty miles from Fort Ellis, N. W. > 0.303 250 .... .... " Territory surface 3 Niverville, Manitoba 1st 12 inches. Brandon, " " Selkirk, " " Winnipeg, " 0.261 0.187 0.618 0.428 3.42 2.66 7.58 5.21 13.1 14.2 12.3 12.2 Rothamsted. I tUSSIAN SOILS. No. 1 12 inches 607 C Schmidt No. 28 467 No. 35 188 44 No. 4 6 130 H No. 5 11 305 (( No. 6 17 281 II No. 79 ' 409 II (1) Calculated on soil dried at 100 C. YC 20929 D OQ ITY OF CALIFORNIA LIBRARY