. Soils and fertilizers . ly found in soils, except when they aresaturated with water. Plants like rice, that grow on water-covered soil, can utilize ammonia; in fact, rice has been foundto make a better growth on ammonium compounds than onnitrates. This is a case in which the plant has evidentlyadapted itself to its surroundings, for upland rice presumablyuses nitrate nitrogen. However, some dry land plants canalso use ammonia. It. has been found, for instance, thatpeas obtained nitrogen as readily from ammonium salts asfrom sodium nitrate. On the other hand wheat plants, whileable to secure
. Soils and fertilizers . ly found in soils, except when they aresaturated with water. Plants like rice, that grow on water-covered soil, can utilize ammonia; in fact, rice has been foundto make a better growth on ammonium compounds than onnitrates. This is a case in which the plant has evidentlyadapted itself to its surroundings, for upland rice presumablyuses nitrate nitrogen. However, some dry land plants canalso use ammonia. It. has been found, for instance, thatpeas obtained nitrogen as readily from ammonium salts asfrom sodium nitrate. On the other hand wheat plants, whileable to secure some nitrogen from ammonia, have been foundto grow much better when they could obtain nitrates. 201. Direct utilization of organic nitrogen by crops. —One of the early beliefs in regard to plant nutrition wasthat organic matter was directly absorbed by plants and that - \fliuf I Y L f / pi .,§ g|jN :: ■ ill ■mm wKf? 7 / #1 1 IM^%M mm f-iI-1 ?.ffflnfi f ■ I .* Hf5^ *ij L ,,.,, T ^^^M ° H ■ 1 :• v: -!m* A |9 4. Plate XII. Fertilizer Tests. — Some soils respond best to onefertilizer constituent, others to another. Note that the best growth ofoats in the upper figure is in the vessels that received nitrogen. In thelower figure the best growth is in the vessel that received phosphoric acid. NITROGENOUS FERTILIZERS 157 it furnished their chief supply of food. Opinion afterwardsswung to the opposite extreme, and it was generally heldthat no organic matter is absorbed by agricultural , however, it has been shown that many crops can usenitrogenous organic matter, and an organic compound calledcreatinin, that has been isolated from soil, was found toproduce a better growth of wheat seedlings than did sodiumnitrate. This may account in part for the high fertilizingvalue of farm manure. Many crops, especially amonggarden vegetables, are most successfully grown only whensupplied with organic nitrogenous materials. 202. Forms of nitrogen in fertilizers. — There
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