Nature of the nitrogenous constituents of soils and their availability to plants
1985
Tilo, S.N. | Magistrado, A.A.
Soils were collected from various parts of the Philippines and analyzed for some chemical, mineralogical, and physical properties. Amounts of hydrolyzable-N generally decreased with depth. Of the acid-soluble N fractions, 23-67% were recovered as labile NH3, 2-60% as amino acids, 1-21% as amino sugars, and 2-56% could not be identified. The acid-soluble forms of N are potential sources of available N while about 14-49% of total N that remained insoluble in 6 N HCl are unavailable N to plants. The study also showed that organic manures and materials varied in their susceptibility to N mineralization. The fertilizing value of azolla, ipil-ipil, a commercial compost, and chicken manure was only equivalent to 60 kg N/ha even if they were applied to supply the equivalent of 120 kg N/ha. This study revealed that in addition to the total N content of organic matter manures, their solubility to 6 N HCl may be used as criterion in predicting their susceptibility to mineralization. However, the final evaluation should be done in plant uptake
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