关键词: 秸秆还田, 氮肥施用, 光合特性, 氮素吸收, 产量形成, 水稻

Abstract:

The rice tillering dynamics, photosynthesis variations during late growth stage, dry matter accumulation, nitrogen uptake and rice grain yield were analyzed at various N application levels with straw returning to the field in a fixed field experiment. There were four straw returning treatments and four N application rates in this trial. Straw returning treatments were 0 kg/hm² (S0),4000 kg/hm² (S4),6000 kg/hm² (S6),and 8000 kg/hm² (S8), respectively. N application rates included 0 kg/hm² (N0),90 kg/hm²(N90),180 kg/hm²(N180),270 kg/hm²(N270), respectively. The results showed that 1) compared with S0, straw returning without nitrogen application obviously inhibited tiller generation and reduced maximum tillering number at rice early growth stage, while increased dry matter accumulation, nitrogen uptake and flag leaf photosynthetic rate at late growth stage, and increased rice grain yield by 2.22%-4.44%. 2) Without straw returning, tiller number was significantly increased with the rising N application rates, and peak tillering time was 7-14 days earlier than N0. Dry matter accumulation and nitrogen absorption during different rice growth stages and rice grain yield increased with the rising N rates, and photosynthetic rate of rice flag leaf maintained a high level at late growth stage. 3) At the same nitrogen application level, rice tiller generation under S4 and S6 treatments was enhanced comparing with S0. Nitrogen absorption at rice mature stage under S6 treatment was significantly increased by 36.58% compared with S0, and photosynthetic rate of rice flag leaf at late growth stage under S6 treatment were higher than S0, while rice tiller generation, photosynthetic rate of flag leaf and nitrogen absorption under S8 treatment did not show favorable results comparing with S6. 4) Straw returning coupled with nitrogen application significantly affected rice effective panicle number and rice grain yield. To compare with N0,S0, rice grain yield at different nitrogen application levels coupled with straw returning was increased by 9.59%-23.51%, and rice grain yield under N180S6 was up to 10.56 t/hm². It was concluded that appropriate straw returning amount coupled with appropriate nitrogen application rate enhanced rice tillering and effective panicle formation, increased rice nitrogen uptake and dry matter accumulation, and then increased rice grain yield.

Key words: straw returning, N application, photosynthetic characteristics, nitrogen uptake, yield formation, rice