在田间定位试验条件下,研究了4个秸秆还田量水平[0 kg/hm²(S0)、4000 kg/hm²(S4)、6000 kg/hm²(S6)、8000 kg/hm²(S8) ]耦合4个施氮水平[0 kg/hm²(N0)、90 kg/hm²(N90)、180 kg/hm²(N180)、270 kg/hm²(N270) ]对水稻茎蘖动态、生育后期光合特性、干物质积累特征、氮素吸收和产量形成的影响。结果表明:1) 不施氮条件下,秸秆还田明显抑制水稻生育前期茎蘖的发生和茎蘖高峰的形成,促进水稻后期的干物质积累、氮素吸收,提高剑叶光合速率,稻谷产量增加2.22%~4.44%。2)氮肥单施条件下,随着施氮量的增加水稻茎蘖数和最高苗数显著增加,分蘖高峰提前7~14d;施氮显著增加水稻各生育期干物质积累量、氮素吸收量和稻谷产量,明显延缓水稻生育后期剑叶光合速率的下降。3) 同等施氮条件下,与S0相比,秸秆还田S4、S6处理促进水稻茎蘖发生,成熟期植株吸氮量显著增加,以S6处理增幅最大,平均增加36.58%,生育后期剑叶光合速率维持在较高水平;S8处理则对水稻茎蘖发生、光合作用和氮素吸收表现出负面影响。4) 秸秆还田耦合施氮量显著影响单位面积有效穗数和稻谷产量,与N0S0相比,两者配施水稻显著增产9.59%~23.51%,以N180S6处理产量最高,达10.56 t/hm²。适宜的秸秆还田量耦合施氮量可促进水稻茎蘖发生和有效穗形成,增加氮素和光合同化物积累,从而增加稻谷产量。

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.