Integration of inorganic and organic nitrogen sources for lowland rice [Philippines]
1986
Descalsota, J.P. | Calabio, J.C. | Evangelista, R.C.
The extent of substituting inorganic fertilizer with organic source was evaluated to determine profitable proportions of these nitrogen sources that can be used in lowland rice. Three soils varying in physical and chemical properties were used. Wet season grain yield data showed that in Maligaya Rice Research and Training Center (MRRTC, Nueva Ecija, Philippines) and farmers' field, 75% inorganic and 25% organic source combination gave yields comparable to those with entire amount as inorganic N source. At the International Rice Research Institute [IRRI, Los Banos, Laguna, Philippines] farm, however, the same combination produced yield one t/ha less than those with prilled urea (PU) alone in the wet and dry seasons. Uptake of N, P, K and Zn generally increased with increase in cropage. At IRRI and MRRTC sites, uptake of these nutrients were enhanced when inorganic fertilizer was the partial or full N source. In Pangasinan [Philippines], however, only N uptake was enhanced irrespective of N source. Organic source on equal nutrient basis is not comparable to inorganic fertilizer either in cost or in return probably because of its high moisture and low nutrient-content. However, farm-produced organic N sources should be able to partially substitute inorganic N fertilizer in lowland rice to minimize dependence on purchased inputs
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