Effect of nitrogen source and insect control on growth of a ratoon crop
1987
Prakash, K.S. | Prakash, B.G. (Agricultural Research Station, Siruguppa (India))
N source and insecticide treatments were studied on a ratoon crop (Sona Mahsuri) in 1985-86. The area has endemic brown planthopper Nilaparvata lugens that could survive in the stubble of a ratoon crop. There were four fertilizer treatments: 0 N/ha, 50 kg N/ha, azolla applied 3-4 times at 2.5 t/ha, and azolla + 25 kg N/ha. The insecticides were monocrotophos at 0.5 kg ai/ha and chlorpyrifos at 0.3 kg ai/ha. Treatments were laid out in a randomized complete block design with three replications. Azolla (fresh weight) was applied on the soil surface 3-4 times, up to 12 t/ha. But the azolla could not be uniformly maintained in the field. Growth and multiplication were retarded by fluctuating water level, snail damage, and high temperature. Soil salinity also could have affected azolla growth. Soils were black deep Vertizols with pH 8.5. N content of the azolla was about 6%. Regenerated tillers were counted at 15 d after ratooning. Plant height, tillers per plant, panicles per plant, sterility percentage, yield, and harvest index were noted at harvest. Number of regenerated tillers, panicles/plant, and yield varied considerably. In most treatments, some tillers regenerated after 15 d. The interaction between N source and insecticide application had no significant effect on ratoon growth and development because there was no pest pressure on either the main or the ratoon crops. Fertilizer at 50 kg N/ha gave the highest mean ratoon yield. Applying azolla immediately after ratooning may not benefit the ratoon crop because azolla N is not available to the plant until the azolla decomposes.
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