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Responses of soybean (Glycine max L.), mung bean (Vigna radiata L.), and corn (Zea mays L.) to CO(NH₂)₂, CaCO₃, Ca(H₂PO₄)₂·H₂O, and CaSO₄, and of legumes to single strain Rhizobium inoculants on a Vertisol was determined during the dry season at Los Banōs, Philippines. Irrigation well water and precipitation were used to maintain soil moisture slightly below saturation in 6-kg crocks. Relevant chemical analyses were made on soils, water, and plants. Inoculation increased N concentration of soybean tops. Soybean yield was greater with seed inoculation before planting than without, but mung bean did not respond to seed inoculation before planting. Neither legume responded to 30 kg N/ha as urea. Nodules on legume roots were greatly increased by 40 kg P/ha. All yields were more than doubled by addition of 40 kg P/ha. Increased yield of corn and soybeans resulted from the addition of 20 kg S/ha. The addition of sulfur as CaSO₄ resulted in an increased soil S concentration as measured by dilute NH₄C₂H₃O₂, CH₃COOH extraction. |
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