不同施氮量下干旱胁迫对棉花生长及种内关系的影响

Effects of drought stress on cotton growth and intraspecific relationship underdifferent nitrogen application rates

土壤水分和氮肥是影响荒漠绿洲区作物生长和种内关系的主要因素。为明确不同施氮量下干旱胁迫对棉花产量以及种内关系的影响,本研究以集群栽培(1穴3株)下棉花为研究对象,设置3种施氮量[300 kg(N)·hm^-2、225 kg(N)·hm^-2、150 kg(N)·hm^-2]和3种水分处理(正常水分、中度干旱胁迫、重度干旱胁迫),测定了不同处理下棉花的生长指标和棉花产量,分析了不同处理下棉花种内关系的变化。结果表明:1)同一施肥条件下,2016年和2017年棉花株高在重度干旱胁迫下显著降低,而茎粗随干旱胁迫加剧显著降低,但叶面积随干旱胁迫加剧却有所增加,且在中度干旱胁迫下的叶面积最大。2)同一施肥条件下,与正常水分相比,中度和重度干旱胁迫下棉花的茎秆生物量均显著下降;叶片生物量和籽棉产量在中度干旱胁迫下最高,在重度干旱胁迫下却降低。3)在当地施氮量300kg·hm^-2下,随着干旱胁迫的加剧,相对邻体效应(relativeneighbor effect,RNE)数值从正值变为负值;在氮肥减少处理(225 kg·hm^-2)下,随着干旱胁迫的加剧,RNE数值先升高后降低,而在施氮量为150 kg·hm^-2处理下,RNE数值随着干旱的加剧逐渐降低,且均为负值。总之,在当地施氮量和中度干旱胁迫下棉花能够获得较高的籽棉产量,且在此处理下棉花的种内关系为助长关系;其他处理均降低了棉花的产量,并使得棉花的种内关系转变为竞争关系。

Soil,water,and nitrogen fertilizer are the main factors which affect crop growth and intraspecific relationships in the desert oasis region,but little is known about the effects of drought stress on interspecific or intraspecific relationships under different nitrogen application rates.This study aimed to investigate the response of yield to drought stress under different nitrogen application rates and analyze changes in the intraspecific relationship of cotton under different treatments.A field experiment was conducted in Gansu Province of China,the growth parameters and yield of cotton were measured,and the changes in intraspecific relationships were analyzed under three nitrogen applications(300 kg·hm^-2,225 kg·hm^-2 and 150 kg·hm^-2)and water treatments(normal water,moderate drought stress,and serious drought stress).The results showed that:1)under the same nitrogen application rate,the plant height of cotton significantly decreased under serious drought stress in 2016 and 2017,and the stem diameter significantly reduced as the drought stress intensified,but the leaf area increased slightly with increasing drought stress and was highest in moderate drought stress conditions.2)The stem biomass significantly decreased in conjunction with decreased water conditions under the same nitrogen application rate,and the leaf biomass and seed cotton yield were highest under moderate drought stress,and decreased under serious drought stress.3)Under the local nitrogen application rate of 300 kg·hm^-2,the relative neighbor effect(RNE)changed from positive to negative with increasing drought stress.The RNE first increased and then decreased with increasing drought stress under the 225 kg·hm^-2 treatment,and the RNE significantly reduced with increasing drought condition and the values were all negative in the 150 kg·hm^-2 treatment.In summary,the combination of local nitrogen application rate of 300 kg·hm^-2 and moderate drought stress resulted in high cotton yield,and intraspecific facilitation.The cotton yield decreased under the other treatments and the interactions all demonstrated intraspecific competition.