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Fertilizer and Legume Experiments Following Sorghums 1
Author(s) -
Conrad John P.
Publication year - 1928
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.2134/agronj1928.00021962002000110010x
Subject(s) - citation , legume , fertilizer , library science , computer science , agronomy , biology
Until recently two theories had been seriously considered to explain the injury that sorghums caused to crops following them. According to one, the sorghum crops take so much of the essential elements from the soil that there is an insufficient amount left in availabie form to meet the normal needs of plant ~owth. According to the other, toxins or "toxic bodies" develop in the soil during the decomposition of the sorghum stubble, which injure the crop plants following. Sewell (8)~ lists other causes which have been suggested. Recently, the writer (3) suggested that another theory worked out ̄ in connection with cereal straws was more applicable to his observations and those of others in the literature than the two formerly considered. According to this theory., the injury is due to competition for available essential elements or ions between the crop plants following the sorghum crop, on the one hand, and the micro-organisms of the soil, on the other hand. The competition of the micro-organisms is made much more effective than occurs under ordinary soil conditions because of the high amount of sugars and possibly other easily decomposable carbonaceous compoundsinthesorghams. These furnish the organisms a source of energy causing them to multiply greatly in numbers. In so doing they would draw from the soil solution ions essential for growth, thereby cutting down the amount left that the crop plants could draw upon. Though no rigorous proof of this theory as the only theory applicable has been established, enough evidence is available to show that i¢ accounts for a considerable amount of the injury. The literature has been previously reviewed (3). Since that time, however, the work of Wilson and Wilson (~) has appeared which adds seill more evidence to support the theory considered by the writer as applicable to the sorghum injury. They give additional evidence that sorghum roots depress nitrates in the soil to a greater extent or for a longer time than do corn roots. Even when the amount of corn roots was increased relative to the sorghum roots so