96 EOARB OF AGRICULTURB. 



of 3'av(l manure. This applied to wheat would give very nearly 

 280 lbs. of potash per acre, and as the growing steers would take 

 out more of the phosphoric acid from the ha}' than potash, 70 lbs. 

 of phosphoric acid per acre. The growth of 30 bushels of wheat 

 per acre would take from the soil 30 lbs. of potash and 24 lbs. of 

 phosphoric acid. Three such crops would exhaust the applied 

 phosphoric acid while but 90 lbs. of the 280 lbs. potash applied 

 would ])e taken. Either one or two views present themselves as 

 inevitable, either yard manure is not a perfect manure or such a 

 spstem of cropping would be faulty. 



Casting about for a good crop to follow this wheat crop we notice 

 that potatoes takes three pounds of potash for every one of phos- 

 phoric acid, while beets require four to one. I name this as an 

 illustration of the principle involved in one direction. Our attention 

 is attracted in another direction in an emphatic way. We find a 

 class of crops whei'e feeding roots are mainl}' found near the surface 

 of the ground and exhaust it mainl}- for food. Yet another class of 

 our farm crops ai-e deeper rooted and feed in a lower layer, while 

 clover and its class feed ver}' largel}' deeper still, or much in the 

 subsoil. Again, some crops make a large root developement, while 

 others oul}' a small root growth. Also we find narrow and broad 

 leaved plants, and plants that make their growth during the first 

 half of the season while others maintain green leaves until frost, or 

 nearly so. The latter two classes stand in different relations to the 

 nitrogen supply as regards each other. The late developed plants 

 being far more independent of nitrogen supply. During the sum- 

 mer b}- nitrification from the organic compounds of the soil nitrates 

 are formed for these crops. The importance of clover in rotation is 

 worthy of a brief notice. B}' its long tap-root clover goes down into 

 the subsoil and gathers up and elaborates in growth the elements of 

 plant nutrition that may have washed below the reach of the roots 

 of ordinary plants. Its broad leaves gather, it is said, more largely 

 from atmospheric sources of plant food. The roots and stubble of 

 clover weigh very heavy, amounting to nearl}' or quite as much as 

 the growth harvested. Dr. Voelker in his investigation of clover 

 found 3^ tons of roots per acre, to the depth of six inches, con- 

 taining as much nitrogen as is found in 37^ bushels of wheat or 

 61 lbs., and 180 lbs for total depth. This has been gathered from 

 sources bej'ond the reach of the roots of ordinar}^ crops. I can onl}' 

 find time to give the practical conclusions of Dr. Voelker, which 



