IC-NRLF SB 75 3fiD LABORATORY MANUAL FOR SOIL FERTILITY CYRIL G. HOPKINS AND J. H. PETTIT LIBRARY COLLEGE OF AGRICULTURE Berkeley. Cai. LABORATORY MANUAL FOR SOIL FERTILITY BY CYRIL G. HOPKINS AND J. H. PETTIT \ NOTE. The student practices described in this laboratory manual are the result of five years' experience by the authors in conducting classes in a course of study in soil fertility. With some modifications the usual chemical methods are employed, specific chemical directions being com- monly based upon those adopted by the Association of Official Agricultural Chemists. Otherwise these practices were originated in this University. The increasing number of students in this institution, and the fact that some other institutions also desire to use our manual, induced us to put it in printed form. Suggestions from other teachers of soil fertility regarding possible im- provements in the manual will be gladly received. THE AUTHORS. College of Agriculture, University of Illinois, Urbana, 111., July, 1905. LIST OF STUDENT APPARATUS. 2 Bunsen burners with rubber hose. 2 Ring stands. 6 Rings (3 sizes). 1 Burette clamp. 2 Triangles, pipe-stem. 2 Erlenmeyer flasks, 200 cc. 2 Erlenmeyer flasks, 300 cc. 2 Beakers, 250 cc. 2 Beakers, 400 cc. 2 Beakers, 600 cc. 2 Kjeldahl flasks, 500 cc. 2 Copper flasks, 500 cc. 1 Bottle, 2500 cc. 2 Bottles, 1000 cc. 2 Bottles, 500 cc. 2 Bottles, 250 cc. 2 Crucibles, 25 cc. 2 Crucibles, 14 cc. i Wash bottle, 1000 cc. 1 Funnel, 15 cm. 2 Funnels, 10 cm. 4 Funnels, 6 cm. 1 Pair crucible tongs. 2 Evaporating dishes, 8 cm. 2 Evaporating dishes, 10 cm. I Graduated cylinder, 100 cc. i Graduated cylinder, 25 cc. i Burette, 50 cc. i Pipette, 25 cc. i Graduated pipette, 10 cc. 1 Desiccator. 2 Test tubes. 1 Double condenser with connect- ing tubing. 2 Watch glasses. 2 Pinch cocks. i Percolator, 500 cc. i Measuring flask, 250 cc. 1 Bone spoon. 2 Safety distillation bulbs with rub- ber stoppers. 1 Pair forceps. 2 Bottles, 400 cc., with corks, i Thermometer, 100 C. 10 Glass battery jars, 5 liters, with i cm. drainage hole in the side, i cm. from the bottom. 2 pieces of iron gauze with asbestos center. 3 C 5784 PRACTICE I. PREPARATION OF A STANDARD HYDROCHLORIC ACID SOLUTION.* By the use of a hydrometer and specific gravity tables prepare five liters or more of approximately one-half normal hydrochloric acid, using chemically pure concentrated acid and ammonia-free water. Standardize by the silver nitrate method : Place exactly 25 cc. (note temperature of stock solution when measured out) of the acid solution, measured with a pipette, in a 300 cc. Erlenmeyer flask, dilute to 75 cc., add at once from a burette sufficient $% silver nitrate solution to nearly, but not quite, precipitate all the chlorin. Close the flask with a clean rubber stopper and shake till the precipitate will settle nearly completely in a short time. Then add the silver nitrate in i cc. portions, shaking after each addition, until the precipitation is complete, avoiding more than I cc. ex- cess of silver nitrate solution. Shake until the silver chlorid settles well, wash three times by decanta- tion (after shaking each time) using about 100 cc. of water containing I cc. concentrated nitric acid per liter and decanting the liquid through a 9 cm. filter. Transfer the precipitate to the filter, dry, transfer the bulk of the precipitate to a watch-glass or crucible, and burn the paper in a weighed crucible. Add 2 to 5 drops of concentrated nitric acid to dissolve reduced silver and then 2 to 5 drops of concentrated hydrochloric acid. Evaporate to dryness without spattering, add the main precipitate, dry to con- stant weight at I20 9 to 130, cool in a desiccator, and weigh. Record the weights of silver chlorid from duplicate 25 cc. portions of the standard hydrochloric acid. *To be done by the instructor. 6 PRACTICE 2. PREPARATION OF A STANDARD AMMONIA SOLUTION. Determine, by hydrometer, the specific gravity of concentrated am- monia and calculate, by the use of a specific gravity table, the number of cubic centimeters necessary to make two liters of approximately one-fifth normal ammonia solution. Sp. Gr , Grams NH 8 per cc Grams NH 3 per liter in normal solution Grains NH 3 in two liters of 1-5 normal solution Cc. of cone. NH 3 equivalent to g. NH 3 Measure out the required amount of concentrated ammonia, add dis- tilled water to make the total volume up to two liters, and mix thoroughly. Standardize by titrating 10 cc. of the standard hydrochloric acid with the ammonia solution, using lacmoid as an indicator. Make three titrations. (1) 10 cc. HC1 is equivalent to cc. NH 3 (2) 10 cc. HC1 is equivalent to cc. NH 3 (3) 10 cc. HC1 is equivalent to cc. NH 3 Average c.c. NH 3 1 cc. NH 3 is equivalent to Mg N. Give reactions in first and second practices, and explain the computa- tions involved in ascertaining the weight of nitrogen in I cc. of the stand- ard ammonia solution. 8 PRACTICE 3. BLANK DETERMINATION OF NITROGEN IN REAGENTS USED IN DISTILLING. Place 250 cc. of ammonia-free water in a copper flask, add 10 cc. of con- centrated alkali solution (made by dissolving 1000 gm. sodium hydroxid and 25 gm. potassium sulfid in 1000 cc. water), pouring carefully down the side of the flask, connect with the condenser, shake the flask thoroughly, heat up- slowly and distill into a 300 cc. Erlenmeyer flask containing 10 cc. of the standard hydrochloric acid and about 15 cc. ammonia-free water. The end of the delivery tube should dip into the acid solution. Distill to a volume of 200 cc. Add lacmoid and titrate with standard NH.3. Titration (1) cc. NH 3 Titration (2) cc. NH 8 Average cc. NH 3 State correction in cc. of standard NH 3 . Explain all reactions involved, including the use of the indicator. 10 PRACTICE 4. PREPARATION OF AN AMMONIUM SULFATE SOLUTION. Weigh out exactly in a weighed crucible the number of grams of chemi- cally pure ammonium sulfate (assuming the salt to be dry) equivalent to 500 cc. of the standard ammonia solution. Dry in the air bath at 115 to 120 for thirty minutes, cool in a desiccator, and weigh. Dissolve in am- monia-free water in a 250 cc. measuring flask. Dilute to exactly 250 cc. Mix well, and transfer to a dry 250 cc. bottle. Label and keep stoppered when not in use. 500 cc. standard NH 3 contains gm. N Percent N in (NH 4 ) 2 SO 4 by theory is 500 cc. NH 3 is equivalent to gm. (NH 4 ) 2 SO 4 Before After ELeating Heating Weight of crucible+(NH 4 ) 2 SO 4 = Weight of crucible = Weight of (NH 4 ) 2 80 4 = Percent dry matter in salt is How much of the ammonium sulfate will it be necessary to weigh out in order to have exactly 5 gm. of the dry salt? 12 PRACTICE 5. DETERMINATION OF NITROGEN IN AMMONIUM SULFATE. Place 10 cc. of the ammonium sulfate solution in a 500 cc. copper flask, add 240 cc. ammonia-free water and then add carefully, by pouring down the side of the flask, 10 cc. of the concentrated alkali. Connect immedi- ately with the condenser, shake the flask thoroughly, heat slowly, and dis- till into a 300 cc. Erlenmeyer flask containing 10 cc. of the standard hydro- chloric acid and about 15 cc. of ammonia-free water, to a volume of 200 cc. Add lacmoid and titrate the excess acid with standard ammonia. Titrations (1) ................................ cc. (2) .................................. cc.NH 3 Average ..................................... cc. NH 3 Mgs. N in sample ..................................... Percent N in dry salt ............................... The percentage purity of the dry salt is ................ Explain all reactions. Does the percentage of nitrogen vary directly or inversely with the ti- tration readings? 14 PRACTICE 6. FIXATION OF BASES IN SOILS. (a) Place a small bunch of glass wool in a percolator, cover with i cm. of clean sand, and add 100 gm. of clayey soil. Upon this carefully pour 250 cc. of dilute ammonium sulfate solution (50 cc. of the solution pre- pared in Practice 4, plus 200 cc. of ammonia-free water). When percola- tion ceases, mix the percolate thoroughly and determine nitrogen in two 50 cc. portions. Titrations (1) cc. NH 3 (2) cc.NH 3 Average , cc. NH 8 Mg. N per cc. in solution used Mg. N per cc. in percolate Percent N fixed by soil (b) Repeat the experiment, using 200 gm. of the same soil. Titrations (1) cc. NH 3 (2) cc.NH 3 Average cc. NH 3 Mg. N per cc. in solution used Mg. N per cc. in percolate Percent N fixed by soil (c) Repeat the experiment, using 200 gm. of sandy soil. Titrations (1) cc. NH 3 (2) cc. NH 3 Average cc. NH 3 Mg. N per cc. in solution used ... Mg. N per cc. in precolate Percent N fixed by soil Give a general reaction for the fixation of bases by soils and explain fully what chemical elements that are important in soil fertility may be retained in soils by means of this reaction. 16 PRACTICE 7. NITRIFICATION. Dilute 20 cc. of the standard ammonium sulfate solution to 500 cc., add. 3 gm. of dipotassium phosphate, 5 gm. of calcium carbonate, and about 2 gm. of fresh rich garden soil. Mix well, let settle, and draw off two loo cc. portions. Place 500 gm. of clean washed and dried white sand in a percolator. Upon this pour 100 cc. of the above solution and immediately wash the sand with about 500 cc. of ammonia-free water, collect the washings and make up to exactly 500 cc. Place 250 cc. portions in copper flasks, add 10 cc. of alkali and determine the nitrogen in the usual way. Compare the amount of nitrogen distilled as ammonia with that originally applied in the ammonium sulfate. Titrations (1) cc. NH 3 (2) cc. NH 3 Average cc. NH 3 Mg. N found Add the other 100 cc. portion of ammonium sulfate solution to 500 grams of clean, washed and dried sand in a percolator and allow to stand in a dark place at warm room temperature for four weeks. Then wash out and determine the ammonia nitrogen as directed above. Titrations (1) cc. NH 3 (2) cc. NH 3 Average cc. NH 8 Mg. N found Percent N nitrified What change has been brought about and how? Explain fully. 18 PRACTICE 8. DETERMINATION OF NITROGEN IN REAGENTS. Measure out exactly 10 cc. of the concentrated alkali in a beaker and dilute to 200 cc. with distilled water. Stir and add slowly (finally drop by drop) concentrated sulfuric acid until the alkali is neutralized, as shown by the change of color. 10 cc. alkali are equivalent to cc. H 2 SO 4 How many cc. of alkali are necessary to neutralize 20 cc. H 8 SO 4 ? Place approximately 2 grams of pure sugar in a Kjeldahl flask, add by measure approximately .650 gm. metallic mercury and 20 cc. sulfuric acid. Digest in a ventilated hood over a low flame till colorless, add carefully, while still boiling hot, powdered potassium permanganate until the solution is green. Allow to cool. Transfer with 200 cc. of ammonia-free water to a copper flask by means of a large funnel supported on an iron ring. Add carefully sufficient concentrated alkali to neutralize 20 cc. of concentrated sulfuric acid, connect with the condenser, shake until thoroughly mixed, and distill as usual. Titrations (1) cc. NH 3 (2) cc. NHa Average cc. NH 8 Check up the standard ammonia solution by titrating against the stand- ard hydrochloric acid solution. Correction for nitrogen in reagents in terms of standard ammonia so- lution cc. Explain the use of the sugar. Give the reaction between the sugar and the sulfuric acid. Why is the mercury used? the potassium permanganate? the potassium sulfid? 20 PRACTICE 9. DETERMINATION OF NITROGEN IN FARM PRODUCE. Each group of students will work upon one of the following materials : 1. Wheat 5. Oats. 2. Corn. 6. Red Clover Hay. 3. Corn Stover. 7. Alfalfa. 4. Corn Cobs. 8. Oat Straw. Weigh out exactly 2 gm. of the material numbered with your group number and determine the nitrogen in it according to the method given in the Eighth Practice. Titrations cc. NH 3 cc. NH 3 Percent N Average cc. NH 3 Calculate the results obtained and with these record the results ob- tained by three members of each group as indicated upon the following page, valuing nitrogen at 15 cents per pound. How many tons of red clover must be plowed under in order to supply in this way the nitrogen for a loo-bushel crop of corn and a 75-bushel crop of oats in a corn, oats and clover rotation ? Compute the pounds of nitrogen required to produce the crops given in the table below. Compute the weight of sodium nitrate (95% pure), which would supply the nitrogen found in these crops, and the cost of the same. KIND OF PRODUCE Pounds N in Produce Pounds NaN0 3 equiv. Cost of NaNO 3 (1) 85 bu. shelled corn (2) 1 200 Ib. cobs (3) stover, wt. equal to (1) -t~ (2) (4) 75 bu. oats (5) 4000 Ib. oat straw (6) 3 tons clover hay Total for three crops PRACTICE 9 (Cont.) NAME OF STUDENT KIND OF PRODUCE Percent N N ii i 1 ton Ib. Value AVERAGE AVERAGE AVERAGE AVERAGE AVERAGE AVERAGE AVERAGE AVERAGE 22 PRACTICE 10. DETERMINATION OF NITROGEN IN ANIMAL EXCREMENTS : SOLID AND LIQUID. Each group of students will work upon one of the following : 1. Horse excrements. 2. Steer excrements. 3. Cow excrements. 4. Sheep excrements. 5. Swine excrements. 6. Poultry excrement and fresh cow's milk. 7. Human excrements. 8. Wheat straw and manger refuse (for bedding). Record age and condition of animals and food rations as nearly as possible in all cases. For solid excrements : Weigh out 10 grams of fresh substance on filter paper, placed on a watch-glass, and transfer both paper and excrement to a Kjeldahl flask. For liquid excrement: Measure out 10 cc. and place in a Kjeldahl flask. Compute weight from specific gravity .................... gm. Solid Liquid. Titrations (1) .............. cc. NH 3 Titrations (1) .............. cc. NH 8 (2) .............. cc.NH 3 (2) ............ cc.NH 3 Average ................... cc. NH 3 Average ............... . . cc. NH 3 Calculate the results obtained and with these record the results obtained by three members of each group as indicated upon the following page. Value N at 15 cents per pound. 10 tons alfalfa hay contain ......................... Ib. N i ton fresh cow dung contains ...................... Ib. N How many tons of fresh cow dung would be required to furnish nitro- gen for 10 tons of alfalfa hay? PRACTICE 10.-(Cont.) NAME OF STUDENT Kind of Manure Percent N Lb. N per ton and value Liquid Solid Liquid Value Solid Value Average Average i Average Average Average Average Average Average 24 PRACTICE ii. DETERMINATION OF NITROGEN IN FERTILIZERS. Weigh out Yz gram of each of the following materials and use 20 cc. of standard hydrochloric acid in the receiver. (a) Ammonium sulfate. (b) Dried blood. (c) Sodium nitrate. (Use the Kjeldahl method modified for nitrates. Mix 2 gm. salicylic acid with the sodium nitrate in flask and add 30 cc. sulfuric acid. Use i l / 2 times the usual amount of alkali in the distillation to neutralize the larger amount of sulfuric acid.) Titrations cc. NH 3 Average corrected cc. NH 3 from sample Percent N Value per ton (N 15c. perlb.) C,H,O, etc. j Are carbonates present in the soil? If the soil is acid, what percent of calcium carbonate is required to cor- rect the acidity ? Suggest a practical method of treatment, of unlimited application, by which the productive capacity of this soil could be profitably increased and permanently maintained. THIS BOOK IS DUE ON THE LAST DATE STAMPED BELOW AN INITIAL FINE OF 25 CENTS WILL BE ASSESSED FOR FAILURE TO RETURN THIS BOOK ON THE DATE DUE. THE PENALTY WILL INCREASE TO SO CENTS ON THE FOURTH DAY AND TO $1.OO ON THE SEVENTH DAY OVERDUE. NOV 2ft tQ4fl{\ *:* g t * <. f . - r -q*} FEB 1 9 1942 rCD JLC7 HBrf* LD 21-100m-7,'40 (6936s) YC 65758 O s CO UNIVERSITY OF CALIFORNIA LIBRARY