水氮调控对轻度盐化土膜下滴灌棉花根干质量的影响

The Effects of Water-nitrogen Regulation on Cotton Roots in Drip-irrigated Salinized Soils

【目的】探究干旱区轻度盐化土条件下水氮调控模式对膜下滴灌棉花根干质量的影响规律。【方法】开展轻度盐胁迫(4~5 g/kg)下膜下滴灌棉花水氮调控对根系干重的影响研究,设置3个施氮水平:300、600 kg/hm^(2)和900kg/hm^(2)(分别记为N1、N2和N3)和3个灌水水平:2750、3750m^(3)/hm^(2)和4750m^(3)/hm^(2)(分别记为W1、W2和W3)共9个处理,分析膜下滴灌棉花根干质量及根干质量密度的差异性变化。【结果】水分对根干质量的作用较氮素明显。相同施氮水平下,根干质量随灌水量增大先增后减。根干质量随着土层深度的增加而减小,适当增加灌水量和施氮量可以促进30cm以下土层中根干质量增加;而在水平方向上,当灌水量偏低时,根干质量在距离滴头较远的水平范围内较其他灌水处理有明显减小的趋势;水氮互作效应对根干质量密度的影响达到极显著水平(P<0.01),随着施氮量的增加,根干质量密度随着土层深度和水平方向的增加而下降。【结论】轻度盐化土膜下滴灌棉花适宜灌溉定额为2 750 m^(3)/hm^(2),适宜施用尿素量为300 kg/hm^(2)。

【Objective】Root growth and its consequence for water and nutrient uptake from soils are modulated by a multitude of biotic and abiotic factors.The aim of this paper is to study the effect of water-nitrogen coupling on the roots of cotton in drip-irrigated salinized soils.【Method】 The experiment was conducted in pots packed with mildly salinized soil(4~5 g/kg),with the local cotton variety Nongfeng 133 used as the model plant.All pots were drip-irrigated.There were three nitrogen(urea) fertilizations:300(N1),600(N2) and 900 kg/hm^(2)(N3),and three irrigation treatments:2 750(W1),3 750(W2) and 4 750 m^(3)/hm^(2)(W3).We measured dry-root weight to compare the difference between the treatments.【Result】 Irrigation affected the roots more significantly than nitrogen fertilization.When nitrogen fertilization was the same,the dry root weight increased first and then fell with the increase in irrigation amount.Along the soil profile,the dry root weight decreased with the soil depth in the 0~40 cm soil layer,and increased with depth in the vicinity of the pot bottom.Increasing irrigation amount and nitrogen application in certain ranges increased dry root weight in the soil below the depth of 30 cm.Horizontally,reducing irrigation amount led to a reduction in dry root weight in the soil distant from the emitter.Increasing nitrogen application did not promote horizontal root growth.The dry root weight decreased along the soil depth,especially in the 0-30 cm soil layer in which the dry root weight declined with depth steadily.The effect of water-nitrogen coupling on the roots was significant(P<0.01).【Conclusion】The effect of nitrogen on the root system was modulated by soil water,and on average increasing nitrogen fertilization negatively affected root growth at significant levels.