. Soils and fertilizers . tter. Thenitrogen contained in a ton of the green crop, when in a con-dition to plow under, is as follows : Table 55. Quantities of Nitrogen in Some LeguminousGreen-Manure Crops Crop Red or mammoth cloverCrimson clover .Alsike clover .... Alfalfa Cowpeas Soy beans Canada field peas . Nitrogenper Ton,Pounds 109101481011 ProbableYield perAcre, Tons Nitrogen per Acre, Pounds 605450112486055 GREEN-MANURES 237 Not all of the nitrogen contained in these crops is takenfrom the air. On soils rich in nitrogen, a considerable pro-portion may be obtained from the soil. On poor s
. Soils and fertilizers . tter. Thenitrogen contained in a ton of the green crop, when in a con-dition to plow under, is as follows : Table 55. Quantities of Nitrogen in Some LeguminousGreen-Manure Crops Crop Red or mammoth cloverCrimson clover .Alsike clover .... Alfalfa Cowpeas Soy beans Canada field peas . Nitrogenper Ton,Pounds 109101481011 ProbableYield perAcre, Tons Nitrogen per Acre, Pounds 605450112486055 GREEN-MANURES 237 Not all of the nitrogen contained in these crops is takenfrom the air. On soils rich in nitrogen, a considerable pro-portion may be obtained from the soil. On poor soils, theproportion derived from the atmosphere is considerablylarger. Soils needing nitrogen most are those that benefitmost largely from its application. 296. Transfer of plant-food materials. — There is a trans-fer of plant nutrients in a double sense : (1) removal of these L055 LAR6ELY ORGANIC *WITH SOME NITR06ENAND PHOSPHORIC ACID ANIMAL TO MARKET LAR6E L055 OF ORGANIC ^MATTER, NITROGEN, PHOS-PHORIC ACID AND POTASH. GREEN MANURE Fig. 34. — Movements of plant-food materials. After absorption by theplant they may be returned in whole or in part to the soil. If grain andstraw or hay are sold nothing but the stubble and roots are returned. Iffed to animals, part may be returned in the manure. If plowed under asgreen-manure, all are returned. substances from combination with other minerals and theirconversion into combinations with organic matter; (2) re-moval from lower soil by absorption by roots and the deposi-tion of this material in the upper layer of soil when the plantdies and is plowed under. The first of these transfers resultsin an improved condition of the plant nutrients, because inthe combinations with organic matter they are in generalmore available to plants than when in combinations with 238 SOILS AND FERTILIZERS inorganic matter. By the second form of transfer the nutri-ents in this available form are deposited in the upper soil fromwhich most crops draw th
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