Increasing nitrogen use efficiency of irrigated rice grown on puddled and non-puddled soil
2016
Girsang, S.S.
The study was conducted to determine the effect of early N applications, puddling, plant spacing, and soil properties on the effectiveness of adjustments in N application at panicle initiation (PI) or later. Rice was grown at the Experiment Station of the International Rice Research Institute (IRRI) in Los Baños, Laguna, Philippines during the wet season (WS) of 2014 and dry season (DS) of 2014/2015 on puddled (block UY) and non-puddled soil (block UE). The soil was a fine, amorphic, isohyperthermic Lithic Haplustept. High N rates at early growth stage increased tiller number, leaf area index (LAI), and plant N at PI. Results suggest that application of N at PI could be adjusted based on early season N application, higher soil N-supplying capacity for puddled than non-puddled soils, and potential yield for the season, which was related to solar radiation. Under conditions of favorable crop growth with adequate irrigation, grain yield was increased by average 355 kg/ha with application of 23 kg urea-N/ha at flowering. Soil inorganic N, anaerobic N mineralization, and bulk density at 16 days after transplanting on non-puddled soil were related to soil N-supplying capacity as determined from rice yield without added N, but they were not effective in predicting the need for N fertilizer, as determined from crop response to added N, Water-filled pore space (WFPS) was a potentially helpful indicator of conditions on non-puddled soil favorable for N losses through nitrification-denitrification.
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