TWAIN ' I - nE ' A RV_AGKH_UU I un.K. D 
 
NEW SERIES. 
 
 VOL. VII. APRIL, 1895. No. 3. 
 
 UPON SOME PROPERTIES OF SOILS, 
 
 WHICH HAVE GROWN A CEREAL CROP AND A LEGUMINOUS CROP 
 FOR MANY YEARS IN SUCCESSION. 
 
 *. 
 
 By SIR JOHN BENNET LAWES, Bart., F.R.S., &c. 
 
 The field upon which our experimental wheat crops are grown is 
 irregular in shape, and the area of the twenty-two experiments for 
 some years differed slightly one from the other, rendering it necessary 
 to make a separate calculation for each in order to bring it into acreage. 
 During the year 1882, thirty-nine years after the commencement of the 
 experiments, it was decided to make the area of all the plots equal, 
 which was done by cutting off a portion of the experimental field at 
 the top and bottom. It is well known that the success of our 
 experiments has greatly depended upon keeping the land as free as 
 possible from weeds, in order that the wheat plants should have to 
 themselves all the food in the soil, and I was very anxious to know 
 what sort of a fight the wheat would make against any vegetation 
 which might spring up if the crop were no longer kept free from weeds 
 by manual labour. Accordingly, instead of cutting the crop upon the 
 portion of land at the top and bottom of the field which would cease 
 to be under experiment, it was left standing to shed its seed for another 
 crop ; so that the whole crop, which in some of the experiments would 
 be over 30 bushels per acre, would be deposited in the land instead of 
 only the two bushels of seed which were sown per acre upon the other 
 portions of the field. The result of this experiment may be summed 
 up in a very few words. Before the next harvest the indigenous 
 vegetation had taken possession of the land to such an extent that 
 nothing to be called a crop was grown in any of the experiments, and 
 in the second and third year the wheat was represented by a few 
 straggling plants which had but a faint resemblance to their original 
 parents ; some of the plants had only one or two small seeds in the ear 
 and the thin stalks were not the least like the straw of wheat. 
 Specimens of the wheat when left to seed itself, with the straw, and 
 a year or two afterwards, are placed in the Museum of the College. 
 
 A reproduction of a photograph to life size of two of the ears of 
 corn for each of the years 1883, 1884, and 1885, accompanies this 
 paper. 
 
 In July, 1886, four years after the top and bottom of the field had 
 been left undisturbed, a careful examination of the vegetation was made 
 by Mr. Willis, and the following is his report " Seventeen orders of 
 
 420041 
 
S-P03 
 
 66 
 
 AGRICULTURAL STUDENTS' GAZETTE. 
 
 plants are represented, being composed of thirty-eight genera and forty 
 species." Particulars of these are given in the following table : 
 
 ROTHAMSTED. 
 
 Experiments on Wheat, 43 years in succession on the same Land. 
 
 List of Plants observed July 27th, 1886, growing on portion of ground 
 
 left to seed itself and uncultivated since Harvest, 1882. 
 
 Botanical Order. 
 
 Botanical Name of Plant. 
 
 Degree of Prominence. 
 
 
 Agrostis vulgaris, var. alba . . . 
 Alopecurus agrestis 
 
 Exceedingly abundant 
 Plentiful 
 
 GRAMINE^E < 
 
 Phleum pratense 
 Poa trivialis ... 
 
 Occasional 
 Moderate amount 
 
 
 Holcus lanatus 
 
 Occaeional 
 
 
 Cynosurus cristatus 
 
 Scarce 
 
 
 Dactylis glomerata 
 
 Scarce 
 
 LEGUMINOS-S: < 
 
 Medicago lupulina 
 Lathyrus pratensis 
 Trif olium repens 
 
 Very abundant 
 Frequent 
 Frequent 
 
 ) 
 
 Trif olium pratense 
 
 Rare 
 
 | 
 
 Ervum hirsutum 
 
 Rare 
 
 RANUNCULACEJE 
 
 Ranunculus repens 
 
 Occasional 
 
 VIOLARIE.K 
 
 Viola tricolor 
 
 Scarce 
 
 CARYOPHYLLE.E 
 
 Cerastium vulgatum 
 
 Frequent 
 
 UMBELLIFEIUE -[ 
 
 JEthusa Cynapium 
 Heracleum sphondylium 
 
 Frequent 
 Occasional 
 
 \ 
 
 Caucalis inf esta 
 
 Frequent 
 
 RUBICE.K 
 
 Galium tricorne 
 
 Occasional 
 
 DlPSACEjE 
 
 Scabiosa arvensis 
 
 Occasional 
 
 
 Sonchus arvensis 
 
 Occasional 
 
 
 Sonchus oleraceus 
 
 Scarce 
 
 
 Taraxacum Dens leonis 
 
 Frequent 
 
 
 Carduus arvensis 
 
 Frequent 
 
 COMPOSITE < 
 
 Gnaphalium uliginosum 
 Tussilago Farf ara 
 Bellis perennis 
 
 Occasional 
 Plentiful 
 Rare 
 
 
 Anthemis Cotula 
 
 Occasional 
 
 
 Centaurea nigra 
 
 Rare 
 
 
 Lapsana communis 
 
 Plentiful 
 
 CONVOLVULACE.E 
 
 Convolvulus arvensis 
 
 Plentiful 
 
 SCROPHULABINE^E 
 
 Veronici agrestis 
 Bartsia odonites 
 
 Scarce 
 Frequent 
 
 BORAGINEJE 
 LABIATE 
 
 Myosotis arvensis 
 Stachys sylvatica 
 Prunella vulgaris 
 
 Frequent 
 Rare 
 Scarce 
 
 PRIMULACE.E 
 
 Anagallis arvensis 
 
 Occasional 
 
 PLANTAGINEJE 
 EUPHOBIACE^E 
 
 Plantago lanceolata 
 Euphorbia exigua 
 
 Rare 
 Frequent 
 
 EQUISETACE.E 
 
 Equisetum arvense 
 
 Plentiful 
 
 In the Autumn of 1894 the ground was again carefully examined 
 by Mr. Willis, when he found twenty-one different orders of plants, 
 which were composed of forty-six genera and fifty-one species, consisting 
 of twenty-two annuals, two biennials, and twenty -seven perennials. 
 A list of the plants observed is given on the opposite page. 
 
 The Leguminous species have spread most wonderfully ; particularly 
 Lathyrus pratensis, which annually yields abundance of seed. Young 
 oak and ash trees, hazel, rose and hawthorn bushes are also to bo found 
 upon the upper portion near the hedge. It would be exceedingly 
 interesting to know what peculiar properties the soil had acquired 
 during this long period of cereal growth to cause such a variety of 
 plants to find food suitable for their growth. The extreme luxuriance 
 of the leguminous plants is especially to be noticed. The soil of our 
 
UPON SOME PROPERTIES OF SOILS. 
 
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68 AGRICULTURAL STUDENTS' GAZETTE. 
 
 wheat field has been carefully sampled and analysed from time to time, 
 and it is very probable that when the soil at the top and bottom of the 
 field is examined we shall find some increase in the nitrogen, which 
 would probably be due to the action of the leguminous plants ; the 
 soil, however, must have acquired properties which are not to be 
 ascertained by ordinary chemical analysis alone,, and might afford an 
 interesting study for those who investigate the minute organisms which 
 play so important a part in animal and vegetable life. 
 
 I will now describe an experiment very similar to the last, in which 
 a field which had been growing a leguminous crop for a great number 
 of years, was allowed to cover itself with native vegetation. In 1848 
 it was decided to grow continuous crops of beans under circumstances 
 with regard to manure, &c., very similar to the experiments upon 
 wheat ; it was, however, found that this crop when continuously grown 
 could not be depended upon under any system of cultivation, and after 
 more than thirty years of very unsatisfactory results, it was decided to 
 give up the experiment. The unmanured bean land would hardly yield 
 a crop equal to the seed sown. Barley and red clover were then taken, 
 but the barley was much injured by the immense growth of the clover 
 amongst it which yielded large crops during the two following 
 years. A considerable part of the field was then turned into the 
 park for permanent pasture ; but about two acres were fenced off 
 so as to prevent any stock going upon it ; and for the last ten 
 years it has been allowed to grow native vegetation without dis- 
 turbance of any kind. Round three sides of the field there are high 
 hedges with a good many trees growing in them ; on the fourth side 
 iron hurdles separate it from the permanent pasture. I should say that 
 this piece of land is more favourably situated for the growth of a great 
 variety of native vegetation than the wheat field, and yet none has 
 come upon it. The vegetation consists of a few tall, tufted growing 
 grasses ; and near one oak tree there are a few small oak trees due to 
 the unconsumed acorn stores of mice. Along the line of hurdles which 
 separates the bean land from the pasture there is abundance of white 
 clover, but none crosses the border. Nothing can be less interesting 
 than the vegetation of this field, or more remarkable as contrasted with 
 that of the wheat field ; a result which was not anticipated, and which 
 at present remains unexplained. When we sow one half of a field 
 with 'corn and see flocks of birds of all descriptions settled there, while 
 none are to be seen upon the unsown portion, we know that the birds 
 find their food on one part of the field and not on the other ; here we 
 have two fields treated exactly alike for long periods of time ; some 
 portions unmanured, some receiving farm-yard manure, minerals only, 
 nitrates, ammonia, &c. ; the only difference being that one has grown a 
 cereal, the other a leguminous crop ; and yet, when put out of cultivation, 
 in one field great varieties of native vegetation find their appropriate 
 food, while in the other only one is to be found ; we know that the 
 birds are attracted by the corn sown, but what attracts the vegetation ? 
 In our rotation experiments, published last year in the Journal of the 
 
UPON SOME PROPERTIES OF SOILS'. 69 
 
 Royal Agricultural Society, there are two sets resembling each other in 
 every respect but one ; two are grown upon land kept entirely without 
 manure ; two are manured with minerals, and two are highly manured ; 
 the only difference between the two sets is, that upon one we have a 
 leguminous crop (beans or red clover) once in four years, while upon 
 the other we have a summer fallow. Thus, therefore, for a period not 
 much short of half a century no leguminous crop has been grown on 
 the latter portion of the experiments. Some years ago a few scattered 
 plants of yellow trefoil were seen amongst the barley on that portion 
 which had grown no leguminous crops. It would have injured the 
 barley if men had been sent in to pull them out, and it was considered 
 that as there would be a summer fallow in the following year the seed 
 would germinate and be destroyed ; at all events as we should have a 
 root crop before we took another barley crop, the fine tilth required for 
 the roots and the constant horse and hand hoeing would secure the 
 germination and destruction of every trefoil seed : such, however, was 
 not the case. Whether " an enemy " had sown the seed, or whatever 
 the cause, the trefoil came up thicker than ever, especially upon the 
 highly manured portions of the field, and it was found to be a very 
 serious and expensive undertaking to get rid of this little pest. It is 
 quite evident that when the land is kept free from leguminous 
 plant-growth, matters accumulate in the soil which are highly favourable 
 to these plants. This is seen both in the experiment just described 
 and in the top and bottom of our wheat field. It is tolerably certain 
 that the matter accumulated does not consist of ordinary manure 
 ingredients, because we cannot grow a leguminous crop continuously by 
 the use of them, as was seen in the bean field : important and interesting 
 investigations could be made on this subject. 
 
 In the rotation experiments it was shown that after the first root 
 crop was removed from the unmanured land no further root crops 
 could be grown ; the plant even ceased to form a bulb. Upon the 
 same unmanured soil both barley and wheat have produced good crops, 
 and in all probability will continue to do so for a very long period of 
 time. The special property of the cereal crops to obtain their food and 
 to continue their growth on the same soil, when plants of other orders 
 fail to do so, appears to be a most important fact when we consider that 
 in some form or other these crops furnish the bulk of the food of the 
 whole world. I am disposed to think that if we could have in 
 succession the climate, that is, the temperature, rainfall, &c., suitable to 
 the various food crops of the world, rice, sugar-cane, maize, &c., they 
 would, if grown upon our wheat field, give results very similar to those 
 we obtain in the growth of wheat ; growing largely increased crops 
 when manured by the same manures, which now increase our wheat 
 crops, and growing continuously without any manure whatever. It has 
 sometimes been suggested that a piece of land which has received no 
 manure for fifty -five years and has grown an average crop of wheat 
 equal to, if not larger than the average crop of the world, must possess 
 some remarkable store of fertility ; I propose therefore to imagine what 
 
70 AGRICULTURAL STUDENTS J GAZETTE. 
 
 might be the possible history of this field in remote times, what was its 
 original fertility, what it has lost of its fertility, and also what it has 
 lost during its half-century of wheat growing. I do not intend to take 
 any notice of those important ingredients in the soil, phosphoric acid 
 and potash, because they exist in much larger quantities than nitrogen ; 
 and also because we have the evidence that when salts of ammonia 
 have been applied to one of the plots which have received no mineral 
 manure since 1844, the crop has been all along and is at the present 
 time larger than the crops which has been manured every year with 
 minerals only. 
 
 The history of the field as far back as we have any absolute record 
 begins in 1623, when a map of that date gives the area of the field, and 
 the hedges as they are at the present time. It was then in arable 
 cultivation and had a broad band of grass round three sides, with a 
 still broader piece of grass at the bottom ; hence probably its name of 
 "Broadbalk." It is by a comparison between the composition of the 
 pasture and the arable part of this field that I propose to get some idea 
 of the original composition of the soil ; but although we have evidence 
 that the exhaustion of the land by continuous wheat crops takes place 
 in the first, second, and third nine inches from the surface, I only intend 
 to refer to the first nine inches. The determination of the nitrogen in 
 the soil of the wheat field was made as early as 1846, but the figures 
 are not to be depended on, as at that time we did not possess the 
 accurate mode of sampling the soil which we employ later on. For the 
 purpose of my present paper I will make use of the analyses which 
 were made in 1865 and again in 1881. The quantity of nitrogen per 
 acre upon the upper nine inches of the soil of the unmanured land 
 amounted to 2,507 Ibs. and 2,403 Ibs., showing a loss in sixteen years 
 of 104 Ibs., or between 6 and 7 Ibs. per acre per annum. The nitrogen 
 in the first nine inches of the pasture at the bottom of the field amounts 
 to 6,200 Ibs. per acre ; and this amount does not differ very much from 
 that contained in the permanent pasture of the park or of a meadow 
 close to the wheat field. Even if we had not the actual evidence as to 
 the field having been in arable cultivation in 1623 we should have no 
 difficulty in deciding that such was the case ; for knowing what we do 
 of the farming of that period it would be impossible to attribute to any 
 other cause such a loss of nitrogen as has taken place since then. The 
 history of agriculture at very early periods gives us very little 
 assistance in endeavouring to trace what would be the character of a 
 soil when it was first taken into arable cultivation. Broderick, in his 
 work upon English land and English landlords, tells us that the soil of 
 England had been very little disturbed by the plough before the 
 invasion of Julius Caesar ; and he says further on, " the practice of 
 agriculture was an instinct and a tradition among the bodies of settlers 
 who formed Roman colonies, nine at least of which were established in 
 Great Britain." During the first four or five hundred years of the 
 Christian era, when the Romans occupied this country, their chief city 
 was " Verulanium," now St. Alban's. Possibly the site might have 
 
UPON SOME PROPERTIES OF SOILS. 71 
 
 been selected on account of the character of the soil ; at all events, 
 when draining was unknown and manure not used it might be 
 considered that a bed of clay upon chalk would be the most suitable 
 soil to select for the growth of corn. I think, therefore, that the land 
 in this district, only four miles from St. Albans and within one mile of 
 a great Eoman road, would very early be selected for this purpose. 
 Unfortunately we do not know what was the actual process of Roman 
 agriculture ; we may, however, assume that two or more corn crops 
 were grown, and that then the land was left to recover ' its fertility by 
 the growth of weeds At all events this was the process adopted 
 several centuries afterwards, for Broderick describes the agriculture of 
 the middle ages as consisting of a crop of barley, oats, or beans, 
 followed by a crop of wheat, and then rest ; the crop of wheat from 
 two bushels of seed giving eight bushels. Not very long after the 
 .Conquest the manor of Rothamsted was granted, although to whom I 
 do not know ; but that it was a very extensive one may be seen by the 
 large number of copy-holders upon the Court-rolls. Where there was 
 a manor there would be a manor house, and although there may have 
 been several before the present one was built, the oldest part of which 
 dates from the time of Edward IV., there is some evidence to show that 
 they stood upon, or not far from the present site ; the woods, the 
 hedges, the fields being very little changed from what they were nearly 
 three hundred years ago, when the property came into the possession 
 of my family. But the question I should like to be able to solve is, 
 What was the nature, the composition of the soil when the first crop 
 of wheat was grown upon it, perhaps fifteen or eighteen hundred years 
 ago ] Although we know something about the timber which was 
 indigenous to Great Britain as distinguished from the trees which were 
 brought over from other countries, I fear the same cannot be said of 
 the native vegetation which covered our fields. Was the deep-rooted 
 lotus or the creeping lathyrus a native 1 As far as I can form an 
 opinion, the land in this district was employed for corn growing at a 
 very early date ; that it went through periods of cultivation and rest ; 
 and that although the soil would be deprived of both phosphoric acid 
 and potash, I do not think that the nitrogen which it contained would 
 be more than that which we find in the present pasture, and probably 
 not so much. Whether the soils resting upon the chalk were or were 
 not in arable cultivation during the Roman occupation, it is quite 
 certain that they have been cultivated with corn crops for a great many 
 centuries ; and if exhaustion of the soil had been possible very little 
 fertility would be left in them. When therefore the term " exhaustion " 
 is used in agriculture it must be understood to refer not to the condition 
 of the land itself but to those ingredients which one farmer puts in the 
 soil and another removes. 
 
 In conclusion, I may point out that however erroneous my views 
 may be with regard to the original fertility of my soil, the fact cannot 
 be ignored that the exhaustion under continued wheat crops without 
 manure has been very slow. Eighteen bushels per acre were grown in 
 
72 AGRICULTURAL STUDENTS' GAZETTE. 
 
 the favourable season of 1894, the last manure applied to the land 
 being fifty-five years ago. Owing to a succession of unfavourable 
 seasons between 1871 and 1883, the average yield of the unmanured 
 land was lower than it has been during the last ten years. Still there 
 is a gradual decline in the crop going on ; and if the seasons were 
 always exactly alike instead of being widely different, we might expect 
 to find this decline exactly the same each year. As I before remarked, 
 the property which the cereal crops possess of obtaining their food 
 from an unmanured soil over very long periods of time, while root and 
 leguminous crops fail to do so, points them out as specially suitable 
 for furnishing the human race with the greater portion of their food. 
 In addition to this property they can be increased very largely and with 
 great certainty by the application of ordinary or artificial manures. If, 
 as appears to be probable, it is further proved that during the exhaustion 
 due to the long continued growth of cereal crops fertility can be restored 
 and a fresh series of corn crops be taken, we see why the exhausted 
 soil of one generation may be the fertile soil of a succeeding one The 
 knowledge that the leguminous plants derive a portion of their nitrogen 
 from the atmosphere has not up to the present time been of much 
 practical advantage to the farmer ; while it was still only an idea, he 
 had already made use of it as far as it would go. We have shown upon 
 our rotation ground where no leguminous crop has been allowed to 
 grow, the violent efforts made by the trefoil to establish itself there. 
 Upon the field which had grown beans until it would grow them no 
 longer, magnificent crops of red clover could be grown ; while upon the 
 wheat land, when put out of cultivation, every sort of native herbage 
 has found food suitable to its requirements. What will be the solution 
 of all these problems 1 Will the day come when seeds are sent out 
 furnished with the appropriate organisms to supply the deficiency in 
 our fields 1 The last half-century has seen the rise of artificial manures 
 and their establishment upon a secure basis ; the next generation must 
 take up a new line of enquiry, and I know none which is likely to lead 
 to more important results, and to be more beneficial to the practical 
 farmer, than an enquiry into the habits of the leguminous plants. 
 
 THE LATE PROFESSOR HARKER. 
 
 In the last number of the Gazette we grieved to mention the very 
 serious illness of Professor Harker : it is with yet greater grief that 
 we now record that the hopes which we ventured to entertain of his 
 recovery and possible return to his beloved ^work at the College proved 
 vain, and that his death took place at his residence, Oakley Villas, on 
 Wednesday, December 19th, 1894, and the funeral in the Cemetery the 
 following Friday. The Principal conducted the service, and there was 
 a large attendance of the Professors and representatives of the Students 
 and scientific bodies. For some few years his health had caused some 
 anxiety, but with characteristic courage he battled bravely with his 
 
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