氮密处理提高迟播栽粳稻资源利用和产量

Nitrogen and density treatment to improve resource utilization and yield in late sowing japonica rice

苏中地区为稻麦两熟制地区,近年来受气候变化和稻虾综合种养规模扩大的影响,水稻迟播迟栽现象较为普遍,使水稻品种的生长发育等与光、温资源不匹配,成为制约水稻高产稳产的重要因素之一。本研究在迟播迟栽(6月12日播种、6月30日移栽)条件下,采用毯苗机插方式,设置4个纯氮施氮量(N_(0):0 kg hm^(-2);N_(240):240 kg hm^(-2);N_(300):300 kg hm^(-2);N360:360 kg hm^(-2))、3个穴栽苗株数(D_(3):3株苗、D_(4):4株苗、D_(5):5株苗)处理,以适播适栽期(5月29日)常规施氮量和穴栽苗株数处理(N300D4)为对照(CK),探究氮肥水平与穴栽苗数对迟播迟栽粳稻生长发育和产量形成的影响,为提升苏中地区迟播迟栽粳稻产量潜力和资源利用效率提供依据。结果表明,较CK相比,迟播迟栽条件下各处理产量均下降,主要原因是迟播迟栽处理群体颖花量显著降低,2年最高群体颖花量分别较CK分别降低11.94%和8.12%;迟播迟栽条件下温光资源利用率降低,植株吸氮量和氮肥利用率降低,导致干物质积累量降低。迟播迟栽条件下,除处理N_(360)D_(5)外,随着施氮量和穴栽苗株数的增加,产量增加。主要原因是提高了群体颖花量,抽穗期叶面积指数和高效叶比例,延长了生育期,从而提高了温光资源利用率,进而提高了成熟期干物质积累量,缓解产量下降;另外,氮肥利用率随施氮量增加呈先增加后下降趋势,N_(300)D_(5)处理氮肥利用率最大。因此,迟播迟栽条件下应首先考虑增加穴栽苗数,再适量增加氮肥施用量,可以缓解产量损失,并提高氮肥利用率。

Recently,the phenomenon of late sowing and late transplanting in rice is becoming more and more common in central Jiangsu,a rice and wheat double cropping system area,which is caused by climate change and the expanding of comprehensive rice-and-shrimp planting model.It will lead to the mismatch of rice growth period with light and temperature resources,restricting the stable high yield of rice.This study was conducted under the condition of late sowing and late transplanting(sowing date was June 12th,transplanting date was June 30th)and the seedling was transplanted by machine.Four nitrogen application rates(N_(0):0 kg hm^(-2);N_(240):240 kg hm^(-2);N_(300):300 kg hm^(-2);N_(360):360 kg hm^(-2))and three density treatments(D_(3):3 seedlings per hole;D_(4):4 seedlings per hole;D_(5):5 seedlings per hole)were arranged,and the suitable sowing period(May 29),conventional nitrogen ap-plication rate,and the seedling number per hole(N300D4)were taken as the controls.Our goal is to explore the effects of nitrogen fertilizer and seedling number per hole on the growth and yield formation in late-sown japonica rice,and to provide theoretical basis for improving yield potential and resource use efficiency in late sowing and late transplanting japonica rice in central Ji-angsu province.The results showed that compared with CK,the yield of each treatment decreased,mainly because of the signifi-cantly reduced spikelet number under the late sowing and late transplanting condition.The highest spikelet numbers were 11.94%and 8.12%lower than those of CK in the two years.In addition,the utilization rate of temperature and light resources,nitrogen uptake,and nitrogen utilization rate decreased under late sowing and late transplanting treatment,leading to a decrease in dry matter accumulation and yield.The yield increased with the increase of nitrogen application rate and seedling number per hole under the late sowing and late transplanting condition,while there was no consistent with the trend under N_(360)D_(5)treatment.We assumed that it was mainly due to the increased spikelet number,larger leaf area index at heading stage,the larger proportion of efficient leaf,and the extended growth period.In summary,the utilization of temperature and light resources and the dry matter accumulation at maturity stage was improved,and the decline in yield was alleviated.Nitrogen use efficiency increased first and then decreased with the increase of nitrogen rate,and N_(360)D_(5) treatment reached the maximum.In general,under the late sowing and late transplanting condition,in order to alleviate the yield loss and reduce nitrogen fertilizer waste,we should increase the seedling number per hole and then increase the amount of nitrogen fertilizer.