杂交水稻

为明确种植紫云英配施减氮处理对双季稻产量、品质、氮素利用效率及氮代谢关键酶活性的调控效应,在福建省龙岩市上杭县中都镇开展大田定位试验。试验设置6个处理,分别为对照N0(冬闲无紫云英还田+不施氮肥)、N100(冬闲无紫云英还田+常规施氮,N 150 kg/hm²)、GN100(紫云英还田22 500 kg/hm~2+常规施氮,N 150 kg/hm²)、GN80(紫云英还田22 500 kg/hm~2+减氮20%,N 120 kg/hm²)、GN60(紫云英还田22 500 kg/hm~2+减氮40%,N 90 kg/hm²)、GN40(紫云英还田22 500 kg/hm~2+减氮60%,N 60 kg/hm²),研究结果如下。(1)产量及其构成因素方面,与N100处理相比,GN100、GN80处理早稻分别增产5.6%～8.8%、3.5%～6.0%,晚稻分别增产7.6%～8.1%、4.7%～7.4%,周年产量分别增加6.5%～8.5%、4.0%～6.6%,有效穗数分别增加5.7%～8.8%、1.1%～3.5%;GN40处理的周年产量显著降低9.5%～9.9%;GN60处理的早稻、晚稻、周年产量与N100处理差异不显著;各施氮处理的每穗总粒数、结实率和千粒重与N100处理差异不显著。(2)稻米品质方面,所有处理的整精米率、垩白粒率和直链淀粉含量差异均不显著,与N100处理相比,GN40处理的蛋白质含量显著降低3.7%～15.9%,晚稻胶稠度显著提高15.3%～16.3%。(3)氮素利用效率方面,与N100处理相比,GN100、GN80处理的氮素总积累量差异不显著,GN60处理降低或显著降低5.4%～8.0%,GN40处理显著降低11.3%～15.0%;GN80处理的氮素稻谷生产效率提高5.6%～8.4%,氮素干物质生产效率提高8.7%～12.7%,氮肥农学效率提高38.6%～63.0%;(4)氮代谢关键酶活性方面,相关分析表明,GS(谷氨酰胺合成酶)和GDH(谷氨酸脱氢酶)活性在不同生育期与氮素总积累量、产量和蛋白质含量之间均存在极显著正相关关系,在灌浆期与直链淀粉含量呈显著负相关关系。综上,紫云英还田配施减氮20%(GN80)可维持较高的有效穗数和每穗总粒数,实现周年增产4.0%～6.6%,并通过调控GS活性来优化氮素利用效率和稻米品质,为双季稻绿色生产提供技术支撑。

To clarify the effects of Chinese milk vetch(Astragalus sinicus L.) incorporation combined with nitrogen reduction on the yield, grain quality, nitrogen use efficiency, and activities of key enzymes in nitrogen metabolism of double cropping rice, a field experiment was conducted in Zhongdu Town, Shanghang County, Longyan City, Fujian Province. Six treatments were established: N0(winter fallow without fertilization), N100(winter fallow+conventional nitrogen application, N 150 kg/hm²), GN100(Chinese milk vetch incorporation at 22 500 kg/hm~2+conventional nitrogen application, N 150 kg/hm²), GN80(Chinese milk vetch incorporation at 22 500 kg/hm~2+20% reduced nitrogen application, N 120 kg/hm²), GN60(Chinese milk vetch incorporation at 22 500 kg/hm~2+40% reduced nitrogen application, N 90 kg/hm²), GN40(Chinese milk vetch incorporation at 22 500 kg/hm~2+60% reduced nitrogen application, N 60 kg/hm²). The results are summarized as follows.(1) About rice yield and its components, compared with N100, GN100 and GN80 increased the early rice yield by 5.6% ～ 8.8% and 3.5% ～ 6.0%, the late rice yield by 7.6% ～ 8.1% and 4.7% ～ 7.4%, the annual yield by 6.5% ～ 8.5% and 4.0% ～ 6.6%, and the number of effective panicles by 5.7% ～ 8.8% and 1.1% ～ 3.5%, respectively. Compared with N100, GN40 significantly reduced the annual yield by 9.5% ～ 9.9%, and GN60 had no significant difference in early rice yield, late rice yield, or annual yield. Compared with N100, different nitrogen application treatments showed no significant difference in total grain number per panicle, seed setting rate, or 1 000-grain weight.(2) About grain quality, different treatments showed no significant difference in head rice rate, chalky grain rate, or amylose content. Compared with N100, GN40 significantly reduced the protein content by 3.7% ～ 15.9% and significantly increased the gel consistency of late rice by 15.3% ～ 16.3%.(3) About nitrogen use efficiency, compared with N100, GN100 and GN80 led to no significant difference in total nitrogen accumulation; GN60 decreased or significantly decreased the total nitrogen accumulation by 5.4% ～ 8.0%; GN40 significantly decreased the total nitrogen accumulation by 11.3% ～ 15.0%. Compared with N100, GN80 increased the nitrogen rice production efficiency by 5.6% ～ 8.4%, the nitrogen dry matter production efficiency by 8.7% ～ 12.7%, and the nitrogen agronomic efficiency by 38.6% ～ 63.0%.(4) About activities of key enzymes in nitrogen metabolism, the correlation analysis showed that glutamine synthetase(GS) and glutamate dehydrogenase(GHD) activities had extremely significantly positive correlations with total nitrogen accumulation, yield, and protein content at different growth stages, and they had significantly negative correlations with amylose content at the grain filling stage. In summary, Chinese milk vetch incorporation combined with 20% nitrogen reduction(GN80) can maintain effective panicles and grains per panicle to increase the annual yield by 4.0% ～ 6.6%, and it can optimize nitrogen use efficiency and grain quality by regulating GS activity, providing technical support for the green production of double cropping rice.