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1.
Summary A pot-culture experiment was conducted to assess the leaching losses of N from the conventional and new nitrogen fertilizers under low-land rice culture. Leaching losses of N were generally less than 20% of applied N with sources other than sodium nitrate and these could be reduced by blending urea with nitrification inhibitor N-Serve or coating withneem cake or by using urea super granules or slow-release N fertilizer sulphur coated urea. These new nitrogen fertilizers were more effective than urea for rice. 相似文献
2.
Summary Two15N-labelled slow-release nitrogen (N) sources, oxamide and isobutylidene diurea (IBDU), each at two particle sizes, and15N-labelled urea were compared at two rates as sources of N for rice (Oryza sativa) under two watering regimes which simulated a transplant (continuous flood, CF) and a direct-seeded (A/F) system of paddy
rice culture.
Highest grain yields were obtained from −8+10-mesh oxamide particles applied at the rate of 2,000 mg of N/5 kg of soil, CF
series; this yield was slightly higher than that obtained from −3+4-mesh oxamide, A/F series. Incubating the N fertilizers
in moist (22% water) soil for 21 days immediately before flooding and transplanting rice greatly reduced N supply because
of nitrification during the preflood period, followed by denitrification after flooding. This resulted in less plant uptake
of N and less grain yield from urea, fine oxamide and IBDU, A/F series. For coarse oxamide, N release during the preflood
period resulted in higher N uptake and grain yield in the A/F rather than in the corresponding CF series.
The pattern of fertilizer N uptake by rice plants was affected by kind of fertilizer, particle size of oxamide and IBDU, and
watering regime. Uptake of fertilizer N generally paralleled uptake of soil N throughout the growth period. Plant tops continued
to accumulate some N during the period of grain filling, but much of the N in plant tops was translocated to the grain after
heading. There was a large decrease in dry weight, N content, and15N content of tops after heading. Root weight and N content increased rapidly at first, and then at a diminishing rate until
maturity.
Unexplained N deficits occurred in the CF series (14–23% of the N applied, depending on N rate and source), and in the A/F
series for IBDU (37–43% of the N applied). 相似文献