壮秧影响不同节氮水平下早稻产量及氮肥吸收利用

【目的】培育壮秧和施用分蘖肥是促进水稻早发的重要措施,但增施分蘖肥易导致水稻无效分蘖增加和氮素流失。研究双季稻区早稻壮秧和分蘖肥节氮条件下产量形成和氮素吸收利用特性,以期为早稻节氮控污和丰产栽培提供科学依据。【方法】以超级杂交早稻‘淦鑫203’为材料,采用壮苗育秧(状秧)和普通育秧(普秧)两种方式培育秧苗。于2014-2015年进行大田试验,设置壮秧常规施氮(VS+100%N)、节氮10%(VS–10%N)、节氮20%(VS–20%N)、节氮30%(VS–30%N) 4个处理,以普秧常规施氮(NS+100%N)处理和不施氮空白(NS+0N)处理分别作对照,共6个处理。减施的氮肥均在分蘖肥中扣除,除不施氮对照外,各处理基肥氮(72 kg/hm^2)和穗肥氮(54 kg/hm^2)均保持不变。分析早稻拔节期、齐穗期和成熟期SPAD值、光合速率、硝酸还原酶活性和各器官氮素含量,并测定成熟期水稻产量及其构成,明确了植株总氮积累量、氮素转运量、氮表观转运率、氮素利用效率等。【结果】与NS+100%N处理相比,壮秧条件下分蘖肥节氮10%~30%对叶片SPAD值和光合速率无显著影响,但壮秧能促进分蘖发生和成穗,在生育中后期可逐渐弥补分蘖肥节氮对分蘖期干物质积累的不利影响,成熟期VS–10%N和VS–20%N处理干物质积累量较对照NS+100%N增加,产量分别增加了8.5%和1.5%;VS–30%N处理干物质积累量和产量则呈下降趋势。同时,壮秧有利于提高早稻叶片硝酸还原酶活性、各器官氮含量和氮积累量,与NS+100%N处理相比,VS+100%N处理成熟期氮素积累量显著增加了6.9%,VS–10%N和VS–20%N处理无显著变化,VS–30%N处理显著下降了9.7%。壮秧处理氮素回收率和氮素农学效率较NS+100%N处理分别显著提高了12.1%~22.4%和9.9%~24.7%(P <0.05)。【结论】双季稻区早稻壮秧可以促进分蘖早发,提高叶片的干物质生产能力和氮代谢性能,弥补分蘖肥减氮后对水稻前期生长的不利影响,提高后期的干物质生产量和氮运转量。通过培育壮秧,分蘖肥减施总施氮量的20%以内,早稻产量不会下降,可实现水稻的节氮、丰产和节本栽培,有利于提高氮素利用效率和减少氮素流失对环境的污染。

Seedling vigour influences nitrogen utilization and yield of early rice under different nitrogen-saving conditions

【Objectives】Vigorous seedlings and topdressing of tillering fertilizer are required for promoting early development of rice. However, tillering fertilizers tend to cause nitrogen loss and ineffective tillering, resulting in low harvest index of rice. The efficacy of nitrogen savings through cultivation of vigorous seedlings was investigated.【Methods】The experiment was conducted from 2014 to 2015, using a super early rice cultivar Ganxin203. The vigour treatment consisted of the vigorous and normal rice seedlings. The experiment included no-nitrogen control and conventional fertilization using normal seedlings (NS+0N and NS+100%N), in which the N rate, 180 kg/hm2 was divided into basal application (72 kg/hm2) and top-dressing of 54 kg/hm2 each at tillering and jointing stages; and four vigorous seedling treatments with N input reduced by 0, 10%, 20% and 30% (VS+100%N, VS–10%N, VS–20%N and VS–30%N). All fertilizer reduction was carried out at tillering stage. The SPAD, chlorophyll content, photosynthetic rate, nitrate reductase activity and nitrogen content of the jointing, heading and maturing stage; grain yield and its components were determined. Then the total nitrogen accumulation, nitrogen transport, apparent nitrogen transport rate and nitrogen recovery efficiency were calculated.【Results】Compared to the NS+100%N, the leaf SPAD values and photosynthetic rates of the VS–10%N, VS–20%N and VS–30%N treatments were not significantly influenced. During the middle and late growth stages, vigorous seedling offset the negative effect of reduced nitrogen fertilizer on dry matter accumulation of the tillering stage by promoting tillering growth and effective panicle number. The VS–10%N and VS–20%N treatments increased dry matter accumulation at the mature stage than NS+100%N and consequently improved rice yield by 8.5% and 1.5%, respectively. However, dry matter accumulation and yield of VS–30%N treatment were significantly lower. Meanwhile, vigorous seedling had higher leaf nitrate reductase activity, nitrogen content and nitrogen accumulation in leaves, stems–sheaths and panicles. Compared to NS+100%N, the total N accumulation in VS+100%N significantly increased by 6.9% while that of VS–30%N decreased by 9.7%. The N recovery efficiency and N agronomic efficiency of the vigorous seedling treatments were 12.1%–22.4% and 9.9%–24.7% higher than those of NS+100%N in the early rice (P < 0.05).【Conclusions】The slow early growth of rice caused by low N input at the tillering stage can be averted by cultivating vigorous seedlings which not only produces more tillers but also exhibits higher dry matter accumulation and nitrogen translocation at the latter stage of the plant development. By cultivation of vigorous seedlings and application of 20%-less N input, the yield of early rice will not decrease, and the nitrogen saving, high yield and cost saving cultivation of rice are realized, which is beneficial to improving the nitrogen utilization efficiency and reducing the environmental pollution caused by nitrogen loss.