FOli JiKTTI'lIt CROPS 



15 



Let us remember that a balanced ration is just as important for 

 corn as for cattle, and that phosphorus is recjuired larg'ely for 

 the g-rain. 



Soils Deficient in Nitrogen — It should be understood that 

 the nitroj,ren in the soil is measured by the organic matter, for 

 the nitrog^en is practically all contained in the org-anic matter. 

 Consequently soils which are deficient in organic matter are also 

 deficient in nitrogen. 



There are two classes of soils which are commonly much more 

 deficient in nitrogen than in other plant foods. These are the 

 very sandy soils and the very rolling or steeply sloping hill 

 lands. 



Improving Sandy L.and — While the sandy lands are not 

 rich in phosphorus and potassium, they are as a rule moderately 

 well supplied with those elements, and such soils are so porous 

 that they afford a very deep feeding range for the plant roots, so 

 that the actual percentage composition in mineral plant food 

 does not fully measure the possible productive capacity of sandy 

 soils as compared with more compact silt or clay soils. 



As a general rule if the three elements, nitrogen, phosphorus, 

 and potassium, be added separately to three different plots 

 of very sandy land, the nitrogen will increase the yield, while 

 little or no increase will be produced by either phosphorus or 

 potassium. After plenty of nitrogen has been provided, then 

 the addition of potassium will still further increase the yield. 

 Actual results obtained on the University of Illinois soil experi- 

 ment field on the sandy land near Green Valley, Illinois, will 

 serve to illustrate this: 



Crop Yields in Soil Experiments 

 Sandy Soil near Green Valley, Illinois 



It will be noted that where nitrogen w^as applied, the yield is 

 more than double that obtained with either of the other elements. 

 Except in 1902, phosphorus shows some effect when added to 

 nitrogen, but potassium with nitrogen is more effective, especially 

 in 1905, when it gave a yield of wheat thirteen bushels higher 

 than was obtained with nitrogen alone. It should be stated, 

 perhaps, that it is exceedingly difficult to select a number of 

 exactly uniform plots for experimental use on this kind of soil 



