不同水分条件下有机无机肥配施对棉花根系特征及产量的影响

【目的】 探究不同水分条件下有机无机肥配施对棉花根系生长发育、干物质积累和产量的影响,为干旱区合理利用水肥资源提供理论依据。【方法】 2018—2019年进行田间定位试验,采用裂区试验设计,主区为重度水分亏缺（W1）、轻度水分亏缺（W2）和正常水分（W3）,控制土壤含水量分别为田间持水量的32%—46%、51%—62%、67%—81%,副区为不施肥（F0）、单施化肥（F1）、30%有机肥+70%化肥（F2）和70%有机肥+30%化肥（F3）,分析不同水分条件下施肥对棉花花铃期根系形态特征、根长垂直分布、根系活力、地上部干物质积累和产量的影响。【结果】 水分亏缺抑制了棉花花铃期根系生长,根长、根表面积、根体积、根系活力较正常水分显著降低,地上部干重下降而根冠比增大,单株铃数和单铃重降低并导致籽棉产量的下降,其中W1负面影响最为严重。不同水分条件下各施肥处理对根系形态特征的影响存在显著差异,W2和W3下,施肥显著增加棉花根长、根表面积和根体积,且有机无机肥配施显著高于单施化肥F1处理,其中W2下,根长、根表面积和根体积随有机肥配施比例的提高而增加,F3较F1处理根长、根表面积和根体积两年平均分别提高18.1%、12.2%和35.0%;W3下,F2处理对根系形态的促进效应最为显著,较F1根长、根表面积和根体积分别提高7.6%、17.0%和20.1%;W1下,各施肥对根长和根表面积具有抑制作用,其中F1处理抑制效应最显著。W2和W3水分条件下有机无机肥配施能够促进20—40 cm土层根系的生长,并显著提高根系在该土层的分布比例,较单施化肥能显著提高各土层根系活力,促进地上部和根系干重的增加并降低根冠比,增加单株铃数和籽棉产量,其中W2下F3处理单株铃数和籽棉产量最高,较F1处理单株铃数和籽棉产量分别提高13.2% 和17.2%,而W3下F2处理单株铃数和籽棉产量表现最高,较F1分别提高16.1% 和9.2%。【结论】 有机无机肥配施能够优化根系形态与空间分布,提高根系活力,促进地上部干物质积累并提高籽棉产量,缓解轻度水分亏缺对棉花根系生长发育的影响。不同水分下有机无机肥配施处理中,轻度水分亏缺下70%有机肥+30%化肥（F3）,正常水分下30%有机肥+70%化肥（F2）为最优施肥处理。

Effects of Combined Application of Organic Fertilizer and Chemical Fertilizer on Root Characteristics and Yield of Cotton Under Different Water Conditions

【Objective】 The aim of this study was to explore the effects of combined application of organic and chemical fertilizer on the growth and development of cotton root system, dry matter accumulation and yield under different water conditions, so as to provide a theoretical basis for rational utilization of water and fertilizer resources in arid areas.【Method】 The fixed position experiments were conducted in 2018 and 2019. The experiment was designed by split block, the main plot treatment consisted of severe water deficit (W1), mild water deficit (W2) and normal water deficit (W3), and the soil water content was 32%-46%, 51%-62% and 67%-81% of the field capacity, respectively. The split-plot treatment was composed of four fertilizer treatments: no fertilizer (F0), single application of chemical fertilizer (F1), 30% organic fertilizer with 70% chemical fertilizer (F2) and 70% organic fertilizer with 30% chemical fertilizer (F3). The effects of fertilizer on root morphological characteristics, vertical distribution of root length, root activity, dry matter accumulation in shoot and yield traits of cotton at flowering and boll stage under different water conditions were analyzed.【Result】 The results showed that the growth of cotton root at the flowering and boll stage was inhibited by water deficit, and the root length, root surface area, root volume and root vitality were significantly reduced compared with normal water. The dry weight of the shoot decreased and the root-shoot ratio increased, then the number of bolls and boll weight per plant decreased, finally leading to a decline in seed cotton yield, while W1 had the most serious negative effect among the water treatments. The effects of various fertilizer treatments on root morphological characteristics under different water conditions were significantly different: the root length, root surface area and root volume were increased by fertilizer treatments significantly, and the combined application of organic and chemical fertilizer were significantly higher than that of single fertilizer F1 under W2 and W3. Under the condition of W2, the root length, root surface area and root volume were improved with the increase of the proportion of organic fertilizer, and F3 had an average increase of 18.1%, 12.2% and 35.0% in 2 years compared with F1, respectively. Under the condition of W3, F2 had the most significant promotion effect on root morphology, which was 7.6%, 17.0% and 20.1% higher than that of F1 on root length, root surface area and root volume, respectively. Under W1, the treatments of fertilizer had an inhibitory effect on root length and root surface area, among which F1 had the most significant inhibitory effect. The combined application of organic and chemical fertilizer could promote the growth of roots in the 20-40 cm soil layer under W2 and W3, and significantly increase the distribution ratio of root. Furthermore, compared with single application of chemical fertilizer, it could significantly increase the root activity of each soil layer, promote the increase of shoot and root dry weight, reduce the root-shoot ratio, and increase the number of bolls per plant and the seed yield of cotton. Under the water condition of W2, the boll number per plant and seed cotton yield under F3 was the highest one, which were 13.2% and 17.2% higher than that under F1, respectively. However, under the condition of W3, the boll number per plant and seed cotton yield under F3 was the highest one, which was 16.1% and 9.2% higher than that under F1, respectively. 【Conclusion】 Combined application of organic and chemical fertilizer could optimize root morphology and spatial distribution, improve root activity, promote dry matter accumulation in shoot and increase lint yield, and alleviate the effects of mild water deficit on cotton root growth and development. With the combined application of organic and chemical fertilizer under different water condition, the optimal fertilizer treatments were 70% organic fertilizer with 30% chemical fertilizer (F3) under mild water deficit, and 30% organic fertilizer with 70% chemical fertilizer (F2) under normal water condition.