June, 1915
T H E J O C R N A L OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
boiling over as a result of violent action, a n d such devices as a water bath’ under t h e generating flasks m a y be dispensed with. Using N/IO solutions for reduction a n d t h e hIitscherlich apparatus, extremely accurate results are obtained quite easily. P R O C E D U R E RECOVNEKDED-The procedure finally recommended for t h e determination of nitric nitrogen in soil extracts, which is t o be designated as t h e 1‘ a1mari - L’lit s che r 1i ch - De v ar d a method, a n d which is regarded as t h e most reliable t h a t has yet appeared, in t h a t it combines t h e strong a n d eliminates t h e weak features of each, is as follows: F o r t y cc. of water. a small pinch of magnesia a n d one of magnesium sulfate are added t o flask D of t h e Mitscherlich a p p a r a t u s (Fig. I). Twenty-five cc. of standard acid a n d 6 0 cc. of neutral redistilled mater are placed in flask F . T w o hundred a n d fifty or 3 0 0 cc. of aqueous soil extract are placed in a joo cc. Kjeldah1 flask, 3 cc. of 5 0 per cent sodium hydroxide a d d e d , t h e mouth of t h e flask closed with a small funnel t o prevent spattering, a n d t h e contents of t h e flask boiled for 3 0 minutes. T h e mater which has boiled off is replaced, a n d , after cooling, I g. of Dei-arda’s alloy ( 6 0 mesh), a n d a small piece of paraffin are added a n d t h e flask connected with t h e a p p a r a t u s ; reduction a n d distillation are carried on for 40 minutes. T h e receiver contents are t h e n cooled, 4 drops of 0.02 per cent solution of methyl red added, t h e excess acid is nearly neutralized, t h e liquid boiled t o expel COS, choled t o 1 0 - 1 j o a n d t h e titration completed. S U M MARY
I--A heduction method is considered t o be preferable for t h e determination of nitric nitrogen in soil extracts. Of such procedures only t h e modified Devarda a n d aluminum reduction methods gave promise of meeting our requirements. 11-Reduction with Devarda’s alloy in hIgO solutions. a n d t h e aluminum reduction method, did not give reliahle results in t h e presence of high organic matter. 111-Reduction with Devarda’s alloy in strongly alkaline solutions renders separation of t h e organic a n d nitric forms of nitrogen almost impossible, requires a larger a m o u n t of alloy t h a n does reduction in solutions S I O in S a O H , a n d t h e reaction is so violent t h a t care must be continually exercised t o prevent a loss of t h e determination. IT-Reduction with Devarda’s alloy in solutions AT I O in N a O H gave reliable results in t h e presence of high organic m a t t e r . I t requires a small a m o u n t of alloy. t h e reaction proceeds quietly, a n d t h e action of such dilute alkaline solutions on organic m a t t e r is very slight. Reduction in solutions N , / 2 0 in NaOH is unreliable in t h e presence of high organic matter. \’-The Mitscherlich a p p a r a t u s is superior t o t h e other distillation devices for t h e manipulation of t h e De var d a method . T71-The method proposed, which combines t h e desirable features of t h e Valmari-Devarda a n d of t h e Mitscherlich-Devarda procedures, a n d which is t o be designated as t h e Valmari-Mitscherlich-Devarda 1
r s e d by W. S . Allen, LOG.c i l .
529
method, is t h e most accurate a n d reliable t h a t has yet appeared for t h e determination of nitric nitrogen in soil extracts. LABORATORY O F S O I L BIOLOGY, OHIOAGRICULTURAL EXPERIMENT STATION,WOOSTER
THE LOSS OF NITROGEN AND ORGANIC MATTER IN CULTIVATED KANSAS SOILS AND THE EFFECT OF THIS LOSS ON THE CROP-PRODUCING POWER OF THE SOIL1 B y C 0. SWANSOX Received January 22, 1915
T h e decrease in t h e crop-producing power of t h e soil is a fact familiar t o all students of agricultural problems. T h e larger productiveness of virgin soils as compared with t h e productiveness of these same soils after they have been under cultivation for several decades is well known by t h e men who broke u p t h e virgin prairie sod a n d have continued t o cultivate t h a t soil for half a lifetime or more. If we make a s t u d y of t h e figures compiled b y t h e State Board of Agriculture for t h e forty-year period, 1872-1911,we shall find t h a t t h e leading crops show a n average decrease i n crop production. I n Brown County t h e average corn production for t h e first twenty-year period, 1872-1891, was 36 bu., a n d for t h e second twenty-year period, 1892-1911, was 3 0 bu. Riley C o u n t y produced a n average of 3 3 b u . in t h e first period, a n d z j bu. in t h e second. I n Sedgwick County, t h e first period shows a n average of 3 2 bu., a n d t h e second 2 1 bu. “ M o r e live s t o c k ” is mentioned b y some people as t h e panacea for this soil. If t h a t b y itself were t h e cure, t h e n a typical live stock county, where more grain is fed t h a n raised, should not show this decrease in crop production. Butler is such a county. I n t h e period between 1872 a n d 1891, t h e average corn production was 3 2 bu. per acre, a n d in t h e second period, 1892-1911,t h e average was 2 6 bu. It is not necessary t o give more figures t o prove this fact. Any one who makes a s t u d y of t h e figures compiled b y t h e State Board of Agriculture will find t h a t there is a n average decrease in crop production a n d t h a t this is t r u e in Butler, Greenwood a n d Chase, typical live stock counties, as well as Brown, Sedgwick a n d Russell, where t h e t y p e is called grain farmipg. Seeds adapted t o climate and soil is a n important factor in crop production. Seed improvement m a y not have made all t h e progress promoters of agricult u r e desire, b u t t h a t t h e seed used b y farmers in general is more a d a p t e d t o t h e climate a n d soil t h a n t h e seed used t h i r t y or forty years ago no student of agriculture will deny. Instruments of tillage have also been improved. T h e better t h e soil is cultivated, other things being equal, t h e greater its crop-producing power. I n spite of these two factors which should have increased t h e a\-erage crop production per acre, we have a decrease. T h e Chemical Department of t h e Agricultural Experiment Station has made a chemical analysis of about 2 5 0 samples of Kansas soil t a k e n from thirteen different counties. These samples are analyzed for total nitrogen, phosphorus, potassium, calcium, or1
Read before the Kansas Academy of Science, December 2 2 , 1914
530
T H E JOURNAL OF INDUSTRIAL A N D ENGINEERING CHEMISTRY
ganic a n d inorganic carbon. Studies in physiological b o t a n y have shown t h a t plants also require iron, magnesium a n d sulfur from t h e soil. B u t agricultural experience a s well as chemical analysis of soils h a s shown t h a t soils are well supplied with these elements a n d for t h a t reason t h e y are not included in our chemical analysis. A s t u d y of t h e figures obtained in t h e chemical analysis of these Kansas soils shows. t h a t t h e elements nitrogen a n d carbon have disappeared from cultivated soils in proportionately larger quantities t h a n t h e other essential elements. T h e o p p o r t u n i t y for making this comparison does not always present itself. Generally a sample is t a k e n t o represent a soil type. If’the field which best represents this t y p e is in cultivation, it may not be possible t o get a sample of t h e . s a m e soil type from a native meadow or pasture. A few such opportunities have presented themselves, a n d t h e d a t a obtained in t h e analysis of such samples form t h e basis of t h e discussion in this paper. T h e soil sample is t a k e n in three s t r a t a : surface ( e 7 in.), subsurface ( 7 - 2 0 in.), a n d subsoil (20-40 in.). Both nitrogen a n d carbon occur t o a greater per cent in t h e surface s t r a t u m . T h e y are a p a r t of t h e organic m a t t e r or t h a t portion of t h e soil which has come from decomposed plant substances. T h e carbon is assumed t o constitute half of t h e organic matter. T h e ratio of nitrogen t o carbon is a b o u t I t o 11. An acre of soil 7 in. deep is assumed t o weigh 2 , 0 0 0 , 0 0 0 lbs. If t h e percentage composition is known, t h e a m o u n t of a n y element per acre can be computed. T h e a m o u n t of carbon is multiplied b y two t o represent t h e organic matter. I n t h e accompanying table are given t h e pounds of nitrogen a n d organic m a t t e r per acre in t h e surface soil. These d a t a are obtained from figures published in Bull. 199, Kansas Experiment Station, a n d from unpublished d a t a on file in t h e D e p a r t m e n t of Chemistry. D a t a for samples of t h e same type t a k e n as close together as,possible have been selected for comparison. I n several cases, t h e sample of t h e cultivated soil a n d t h e uncultivated soil were t a k e n only a few rods a p a r t , I n cases where no sample of the cultiv a t e d soil is directly comparable with t h e uncultiv a t e d soil on account of location a n d known history, t h e average of several cultivated soils is used. This makes a fair comparison. It is t r u e t h a t occasionally a sample from a cultivated field shows a higher percentage of nitrogen a n d organic m a t t e r t h a n a sample from t h e same t y p e in a virgin field. Such cases are noticed in t h e ‘ r e p o r t of t h e soils of Shawnee C o u n t y , published in Bull. 200, Kansas Experiment Station. I n these cases t h e cultivated soil h a s received special care a n d t h e uncultivated soil represents a very poor phase of t h e t y p e . F r o m t h e original d a t a presented in Table I, t h e figures in Table I1 are calculated. “ T h e pounds loss of nitrogen’’ is t h e difference between t h e a m o u n t of nitrogen in t h e virgin soil a n d t h a t in t h e cultivated soil. This difference varies from 1 2 0 0 t o 1800 lbs. per acre. Soil sample 1 0 3 2 from Greenwood C o u n t y was t a k e n from a field which h a d been cultivated t o
COUNTY
SOIL TYPE
Riley
Oswego silt loam
Brown
Marshall silt loam
TABLE I LBS. PER ACRE Soil Org. DESCRIPTIOW N matter No. 1024 Native meadow., , . . . . . . . . 4980 122,400 1023 Continuous grain cropping about 30 years (wheat and . . 3700 85,600 1052 Average of 6 cultivated soils, t h e highest nitrogen 4560, and organic matter 111,600. Rotation of corn, oats, clover and w h e a t . . . . , . . . 4240 106,800 1037 Native buffalo grass, in ,pasture ...... , . , , , . . . . . . . . . . 4260 98,400 at 1036 30 yrs. growing . , 2960 64,400 . . 3760 83,600 1093 Native me 1094 Cultivated (corn a n d broom corn) ........ , . . , , , , , , , . . 2440 46,400 1127 Native pasture.. , , , . . , , . , . . 4280 106,400 1128 Cultivated (corn a n d forage . 2800 66,800 . . 4600 113,600 1031 , , . . . . . . . . . . 3400 1032 73,200 1219 , . . _ .. . . . 4800 112,400 1258 Corn a n d forage crops.. . . , . . 3600 76,400 1034 Catalpa grove.. , , , . , . . . , . . . 5200 126,000 Average of 5 cultivated samples, the highest nitrogen 4200, a n d organic matter 90,000. Corn and forage crops . . . . . , . , . , . , . , , , . .. . 3400 76,400 1071 Native p a s t u r e . , , . . . . . , . . 3400 74,800 Average of 3 cultivated soils cultivated mostly t o wheat 1920 36,400
.
.
....
...
-. Russell
Sedgwick clay loam
Allen
Oswego fine sandy loam
Butler
Sedgwick clay loam
Greenwood Osage silty clay loam Greenwood Osage silty clay loam Greenwood Summit silty clay loam Reno
Vol. 7 , No. 6
Reno loam
.
.
. .
corn for t h i r t y years. T h e comparison sample of uncultivated soil was t a k e n from a native meadow, a few rods away. Sample 1034, Greenwood C o u n t y , t a k e n in a catalpa grove, shows a higher content of nitrogen a n d organic m a t t e r t h a n a n y of t h e virgin soils, except soil sample 1 0 5 2 , t a k e n in a native meadow in Brown C o u n t y . T h a t indicates t h a t as far a s this comparison goes, t h e soil in t h e catalpa grove shows no tendency towards depletion of nitrogen or organic matter. T h e sample of soil t a k e n in a field cultivated t o corn a n d forage crops next t o t h e catalpa grove, showed a nitrogen content of 3700 a n d organic m a t t e r t o t h e extent of 8 9 , 2 0 0 lbs. per acre in the surface soil, or a difference of 1 , j o o lbs. nitrogen a n d 36,800 lbs. organic m a t t e r in favor of t h e soil in t h e catalpa grove. TABLEI1
Riley Riley Brown Brown Russell Russell Allen Allen Butler Butler Greenwood Greenwood Greenwood Greenwood Greenwood Greenwood Reno Reno
iYative Cultivated Native Cultivated Native Cultivated Native Cultivated Native Cultivated Native Cultivated Native Cultivated Native Cultivated Native Cultivated
POUNDS Loss PER CENTLOSSPer cent 7 . N in Org. Org. org. N matter N matter’ matter . . . . . . . . 4.07 .... 4.32 1280 36800 25.7 30.7 , , .. .... 3.93 i i i o jiioo 22.6 2 3 . 3 3.97 4.33 ijoo 34000 30:s 3i:i 4.60 4.50 5.26 i3io iiioo 3s:i i480 39600 . . . . . . . . 4.02 4.19 34.5 37.2 , . . . . . . . . . . . . . . . . 4.05 4.64 1200 40400 26.1 35.6 iioo 36000 . . . . , . 4 . 2 7 4.71 25.0 32.0 . . . . . . . . . . . . . 4.13 4.45 49600 34.6 40.0 . . . . 4.55 5.28 1480 38400 4315 51.3
4415
.
i800
.
Ratio of N and C in organic matter 1 : 12.2 1 : 11.6 1 : 12.7 1 : 12.6 1 : 11.5 1 : 10.7 1 : 11.0 I : 9.7 1 : 12.7 1 : 11.9 1 : 12.3 1 : 10.8 1 : 11.7 1 : 10.6 1 : 12.1 1 : 11.2 1 : 11 1 : 9.5
W h a t does t h e loss of 1 2 0 0 lbs. of nitrogen from t h e surface soil of a n acre of land mean? T o produce one bushel of corn t h e soil must furnish I lb. of nitrogen for t h e grain a n d ‘ / z lb. for t h e stalks a n d cobs. T h e 1 2 0 0 lbs. of nitrogen represent t h e a m o u n t needed to produce 800 bu. of corn, stalks a n d grain, or ~ 6 * / ~ b u . per acre for 30 years, assuming t h a t everything is removed from t h e land a n d t h a t no nitrogen is lost in t h e drainage water. Such farming practice would. be possible only with virgin soils well stocked with nitrogen a n d organic matter. Crops use a certain per cent of t h e nitrogen in t h e soil a n d for t h a t reason
J u n e , 191j
T H E JOL-RIVAL O F I , V D r S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
complete soil exhaustion is impossible. B u t soils are considered exhausted when t h e t o t a l a m o u n t of plant food possible for t h e crop t o obtain is less t h a n is required t o produce a profitable crop. If a soil h a s been cultivated for t h i r t y years t o corn a n d has produced an average of 26 b u . per acre during this time, i t will not be possible t o produce this a m o u n t of corn i n t h e next t h i r t y years with t h e same method of farming practice. It is a common observation of farmers t h a t i t takes more work t h a n formerly t o produce crops. Cultivation is one of t h e means of producing usable plant food. I n new soils t h a t plant food which is most easily made usable is transformed first. When this has been used u p t h e first flush of a b u n d a n t crop production passes a n d more work is required b y t h e farmer. I n t h e third a n d fourth columns of Table I1 are shown t h e percentage losses of nitrogen a n d organic m a t t e r . T h e per cent loss of nitrogen varies from 2 2 . 6 per cent in sample from Brown C o u n t y t o 43.5 per cent in t h e samples from Reno County. T h e next greatest losses are found i n t h e samples from Butler a n d Greenwood Counties, where according t o t h e popular conception t h e farmers have t h e means of conserving soil fertility. Brown C o u n t y shows t h e smallest loss and in this p a r t of t h e s t a t e proper syst e m s of crop rotations have been used more. T h e per cent loss of organic m a t t e r varies from 23.3 in t h e Brown C o u n t y samples t o j1.3 in t h e Reno County samples. I n every case t h e percentage loss of organic m a t t e r is greater t h a n t h e percentage loss of nitrogen. These figures show t h a t t h e cultivated soils of Kansas have lost on t h e average more t h a n one-third of their original stock‘of organic matter. T h e seriousness of this situation cannot be overemphasized. K h i l e these figures show t h e percentage of t o t a l loss, t h e y do not tell anything a b o u t t h e quality of organic m a t t e r lost. This fact will be discussed later. I n t h e fifth column of Table I1 is found t h e per cent of nitrogen i n organic m a t t e r . In every case t h e per cent of nitrogen is greater in t h e cultivated soils t h a n in t h e virgin soils. Chemically, carbon is t h e more active element. As organic m a t t e r becomes old i t becomes more inert. T h e chemical changes are slower a n d t h e response of t h e soil is more sluggish. Column six gives t h e ratio of nitrogen t o carbon i n organic m a t t e r . T h e widest ratio is found i n virgin soils a n d t h e narrowest in t h e cultivated soils. T h e average of t h e native soils is I : I z a n d of t h e cultivated soils, I : I I . I. W h a t is t h e significance of this ratio? E. J. Russel states in his book “Soil Conditions a n d P l a n t Growth,” t h a t t h e ratio between nitrogen a n d carbon in stubble is I : 40 a n d i n legumes I : 2 j . Most of t h e organic m a t t e r in Kansas soils has come f r o m t h e prairie grass. A number of samples of prairie h a y analyzed at t h e Chemical Department of t h e Experiment Station have shown a n average nitrogen content of 0 . 8 j per cent. This is, a very low nitrogen content a n d would compare very well with t h e stubble t o which Russel refers. As there are some native legumes this would influence t h e ratio. T a k ing t h e ratio of nitrogen t o carbon in t h e native
531
vegetation as I : 36 would not be a n unfair assumption. If t h e ratio of nitrogen t o carbon in virgin soil is I : 1 2 , i t means t h a t it would have t a k e n three pounds of native vegetation for each pound of organic m a t t e r found i n t h e soil, provided there h a d been n o loss of nitrogen i n t h e process of transforming t h e native vegetation into such organic m a t t e r as is found in t h e soil. B u t it does not require a n y extensive s t u d y of t h e organic chemical changes which go on in t h e soil t o know t h a t great losses d o occur. This discussion is made for t h e purpose of showing t h e enormous a m o u n t of native vegetation required t o produce t h e organic m a t t e r in t h e soil, a n d in this discussion we leave o u t t h a t present below t h e surface soil a n d this i n t h e aggregate would a m o u n t t o a b o u t twice t h a t in t h e surface soil. Most of t h e native prairie soils in Kansas contain over I O O . O O O lbs., or j o tons of organic m a t t e r in t h e surface soil of one acre 7 in. deep. On t h e basis of t h e above discussion, which is founded on chemical facts with t h e estimate less t h a n what is known t o actually t a k e place, i t has t a k e n more t h a n 1 j 0 t o n s of native vegetation t o produce t h e organic m a t t e r found in our native prairie soils. If, t h e n , over one-third of this organic m a t t e r h a d been lost from our soils after less t h a n fifty years of cultivation, i t makes t h e thoughtful m a n stop a n d consider. Organic m a t t e r is t h e life of t h e soil. Organic m a t t e r is of very little value in t h e soil unless i t is undergoing chemical changes. This chemical change cann o t t a k e place without loss in t h e a m o u n t of organic m a t t e r . When organic m a t t e r decays i t forms a number of substances a n d m a n y of these are indispensable for t h e proper functioning of t h e soil. I t is these chemical changes which narrow t h e ratio between nitrogen a n d carbon a n d cause t h e consequent loss of t h e a m o u n t of organic matter. T h e loss of organic m a t t e r is n o t of itself a n evil. Unless i t does t a k e place, t h e soil will not be fertile. I n nature t h e raw materials for these transformations are supplied. T h e evil consequences follow when man upsets t h e order of n a t u r e a n d fails t o supply t h e raw materials which are used up. There are seven of nature’s essentials for profitable crop production; namely, good seed, proper a m o u n t of light , suitable temperature, proper physical a n d biological conditions of t h e soil, a n adequate a m o u n t of moisture, a n d plant food. T h e organic m a t t e r of t h e soil is directly connected with a n d influences all these conditions except seed a n d light. T h e d a r k color’of t h e soil is due t o organic matter, a n d dark-colored soils warm up faster t h a n those of lighter color. Soils well stocked with h u m u s drain better, a n d well drained soils are warmer t h a n wet soils. T h e organic m a t t e r increases t h e water-holding capacity of s a n d y soils a n d prevents t h e s a n d from washing a n d blowing. T h e organic m a t t e r gives clay a n d silt soils a better structure resulting in better tillage a n d drainage properties. Organic m a t t e r furnishes food for t h e countless microorganisms i n t h e soil; without these, plant food cannot be prepared. T h e chemical
53 2
T H E J O 1 l R N A . L O F I - V D C S T R I - A L A,VD ELVGIAVEERILVGC H E M I S T R Y
reactions directly associated with a n d d u e to organic m a t t e r are t h 8 greatest agencies in t h e soil for making usable plant food from t h e materials stored u p in t h e rock powder which makes u p t h e great portion of t h e soil. Farmers in m a n y p a r t s of t h e s t a t e are complaining of t h e development of gumbo spots in their fields. T h e majority of such spots, observed b y t h e writer, are d u e t o t h e loss of t h e original surface soil, either through soil blowing or soil washing. Where listing is done u p a n d down ‘the slopes i t does n o t t a k e m a n y years t o remove t h e original surface soil. I n t h e drier p a r t s of t h e s t a t e , blowing will accomplish t h e same result. T h e evil of soil blowing increases with t h e disappearance of organic m a t t e r in t h e soil. T h e organic m a t t e r causes t h e fine soil particles t o adhere together in larger aggregates called soil grains, a n d these a r e n o t moved b y t h e wind. When t h e organic m a t t e r is used up. these soil grains are reduced t o d u s t which blows easily. Soil washing does n o t t a k e place where t h e soil is open so t h a t t h e water is soaked u p b y t h e soil. Organic m a t t e r gives clay a n d silt soils a n open structure which enables t h e water t o enter t h e soil; besides, i t binds t h e fine clay particles together so t h a t t h e y are less easily moved b y water in motion. Sgricultural writers a n d speakers have a great deal t o say a b o u t t h e evil of depleting soil fertility b y t h e system of grain farming, a n d more live stock is urged as a remedy. As a m a t t e r of fact, one system is not t o blame altogether a n d t h e other system will not necessarily offer t h e remedy. If t h e farmers of B a r t o n C o u n t y deplete their soil fertility a n d particularlyorganic m a t t e r b y exclusive wheat farming a n d straw burning, a n d t h e farmers of Butler C o u n t y continually harvest forage crops from their cultivated fields a n d feed these forage crops as well as imported grain on t h e banks of a ravine, there i s no difference between these syst e m s as f a r as t h e y affect soil fertility. T h e ultimate purpose of farming is t o produce substances which can be used for h u m a n food, clothing a n d shelter. Forestry rightly practiced does not deplete soil fertility. T h e cotton lint does n o t deplete t h e organic m a t t e r a n d soil fertility. T h e depletion is due t o t h e removal of t h e cottonseed together with t h e rest of t h e plant. T h e a m o u n t of fertility removed in t h e animal carcass used as h u m a n food is comparatively small a n d can be easily restored. Four-fifths of t h e element phosphorus, one of t h e limiting elements in soil fertility, goes into t h e bran a n d shorts when flour is manufactured for h u m a n food. T h e small a m o u n t removed i n flour can easily be restored t o t h e soil. Wheat farming depletes soil fertility because straw is burned or wasted a n d b r a n a n d shorts are exported. Because dairy farming exports only such substances as can be used directly as h u m a n food, i t keeps u p t h e organic m a t t e r of t h e soil better t h a n m a n y other systems of farming. T h e discussion in this paper has shown t h a t i t has t a k e n more t h a n I j o tons of native vegetation t o produce t h e organic m a t t e r in t h e surface soil. If we accept this very conservative assumption a n d also
Vol
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know t h a t one-third of t h e organic m a t t e r present in t h e virgin soils has been lost in less t h a n fifty years of farming, i t mean5 t h a t t h e least a m o u n t of organic m a t t e r necessary t o return t o t h e soil every year is one t o n per acre in addition t o w h a t is now returned in stubble a n d cornstalks. I n addition t o returning such substances as s t r a w a n d f a r m manures, some substance must be added which restores t h e nitrogen removed in grain. -4 bushel of corn takes I lb. of nitrogen, a n d a bushel of wheat 1 ~ # 3lbs. T h e best means of obtaining t h i s nitragen is b y growing legumes such as alfalfa. B u t this nitrogen will not be restored t o t h e soil if all t h e h a y is exported from t h e farms. Some of t h e best agricultural investigators are of t h e opinion. based OR scientific experimentation, t h a t legumes on t h e average t a k e only as much nitrogen from t h e air as is found i n t h e hay. T h e growing of alfalfa, if grown for export. will n o t solve t h e problem of soil fertility a n y more t h a n live stock farming when t h e fertility is wasted on t h e banks of a ravine. I n all our discussions of problems of soil fertility we m u s t not forget t h e peculiarity of t h e K a n s a s climate. We shall never be able t o practice such a h a n d t o m o u t h system as is possible i n a climate of greater a n d more even rainfall. T h e soils m u s t have a greater resistance against both excessive wet weather a n d d r y weather. This resistance depends more on t h e content of organic m a t t e r t h a n on a n y other factor. We have seen t h e enormous a m o u n t of native vegetation i t has t a k e n t o produce this organic m a t t e r , a n d t h e very large loss in less t h a n fifty years of farming. T h i s enormous loss of organic m a t t e r is t h e most serious problem in soil fertility in t h e s t a t e of Kansas. S TJ M 41A R Y
1-The soils of Kansas show a n average decrease in crop-producing power i n spite of t h e fact t h a t farmers use seed which is better a d a p t e d t o climate a n d soil, a n d improved methods of tillage. 2-Results based on chemical analysis of cultivated a n d uncultivated soils in seven representative counties show t h a t t h e elements carbon a n d nitrogen have disappeared from t h e cultivated soils t o t h e largest extent. These cultivated soils have lost from 1 2 0 0 t o 1800 pounds of nitrogen, a n d from 32,400 t o 49,600 pounds of organic m a t t e r per acre in t h e surface soil. On a percentage basis this a m o u n t s t o from 2 2 6 t o 4 3 . 5 per cent of t h e nitrogen, a n d from 2 3 3 t o j~ . 3 per cent of t h e organic m a t t e r . It means t h a t these soils h a v e lost in round numbers from one-fifth t o twofifths of t h e nitrogen, a n d f r o m nearly one-fourth t o one-half of t h e organic m a t t e r . 3-Decay of organic m a t t e r is t h e life of t h e soil. -4 comparison between t h e ratio of nitrogen a n d carbon in vegetable m a t t e r a n d in t h e organic m a t t e r of t h e soil shows t h e enormous a m o u n t of vegetable m a t t e r i t has required t o produce t h e organic m a t t e r in t h e soil. T h e loss of one-third of this organic m a t t e r together with t h e accompanying nitrogen loss is t h e most i m p o r t a n t cause of t h e decreased crop-producing power of t h e soil. KANSASSTATE AGRICVLTURAL COLLEGE,MANHATTAN
