不同土壤湿度对膜下滴灌棉花根系生长和分布的影响

 【目的】精量制定膜下滴灌棉花的田间水分管理制度和揭示滴灌棉花的增产机理。【方法】以田间试验为基础，设置90%θf、75%θf和60%θf（θf田间持水量）3个土壤湿度处理，在棉花不同生育阶段采用双向切片法测定棉花根系和根冠比;用时域反射仪测定土壤水分;最终测棉花产量。【结果】3个土壤湿度所对应的棉花根系生长过程呈“S”形变化，但是，由于75%θf处理的棉田土壤含水量始终处于适宜范围内，全生育期棉花根系生长速度快及最终根重大;90%θf处理的土壤水分太充足，根系生长速度缓慢，其根区土壤中根重最小;60%θf处理的根重介于其它2处理的根重之间。3个处理的棉花根重垂直分布呈锥形负指数递减模式，且随土壤湿度提高，深层根重减小幅度大，根系变浅。0～30 cm土层中，75%θf处理的棉花根系所占总根重比例最高。水平方向上棉花根系主要分布在膜下窄行和宽行土壤中，膜外裸地中根重很小;各土壤湿度处理中，75%θf处理下膜下窄行或宽行的根重都比90%θf和60%θf处理的根重大。棉花根冠比随着土壤湿度的增加有减少的趋势。不同土壤湿度处理对棉花产量有不同的影响，75%θf处理下的产量最高。【结论】膜下滴灌条件下土壤水分持续维持较高水平，对棉花根系生长及产量有不利的影响。

Effects of Soil Water Content on Cotton Root Growth and Distribution Under Mulched Drip Irrigation

【Objective】 The relation between soil water content and the growth of cotton root was studied for the scheme of field water and cotton yield under mulched drip irrigation. 【Method】 Based on the field experiments, three treatments of soil water content were conducted with 90%θf, 75%θf, 60%θf (θf is field water capacity). Cotton roots and root-shoot ratio were studied with digging method, and the soil moisture was observed with TDR, and cotton yield was measured. 【Result】 The results indicated that the growth of cotton root accorded with Logistic growth curve in corresponding three treatments of soil water content, the cotton root grew quickly and its weight was very high under the soil water treatment of 75%θf because of the suitable soil water condition, grew slowly and its weight was lower in the soil of the treatment of 90%θf beyond the suitable soil water condition, and the root weight was mediate under the soil water treatment of 60%θf. For the three water treatments, the cotton root weight decreased with soil depth, and decreased extensively in deeper soil layer with the soil moisture increment. Compared with other treatments, the ratio of cotton root weight in 0-30 cm soil layer to the total root weight was the highest under the soil water treatment of 75%θf. The cotton root system was distributed mainly in the soil narrow row and wide row mulched with plastic film, and the distribution of root was small in the soil outside plastic film. Compared with other treatments, the weight of cotton root was the highest in the soil narrow row or wide row mulched with plastic film under the soil water treatment of 75%θf. Root-shoot ratio decreased with the soil moisture increment. The soil water content affected cotton yields, and cotton yield was the highest under the soil water treatment of 75%θf. 【Conclusion】The sustained higher soil moisture level is unfavorable to the growth of cotton root system and yield of cotton under mulched drip irrigation.