干旱区膜下滴灌条件下土壤深层水对棉花根系生长、分布及产量的影响

在土柱栽培条件下研究膜下滴灌土壤深层水对棉花根系生长的影响及与植株地上部生长的关系，设置土壤(60～120 cm)有深层水和无深层水2个处理，每处理设2个生育期间灌溉处理，分别为田间持水量70%和55%.结果表明：棉花总根质量密度、40～120 cm土层根长密度、根系活力等与地上部干质量间均具有显著的相关关系.生育期间耕层70%田间持水量条件下，土壤有深层水处理的总根质量密度与无深层水处理无明显差异，但40～120 cm土层的根长密度增加，根系活力增强，提高了土壤贮备水消耗量，增加了地上部干质量，最终获得较高的经济产量及水分利用效率.土壤有深层水条件下，生育期间耕层55%田间持水量处理的根冠比较大，40～120 cm土层根长密度和80～120 cm土层根系活力相对较高，土壤贮备水消耗量大幅提高，但仍无法弥补生育期间水分亏缺对根系及地上部生物量造成的负面影响，导致经济产量显著低于70%田间持水量处理.综上，充足的土壤深层水配合生育期间耕层65%～75%田间持水量，可促进棉花根系向下生长，有利于实现膜下滴灌棉花节水高产高效生产.

Effects of water storage in deeper soil layers on the root growth, root distribution and economic yield of cotton in arid area with drip irrigation under mulch

Taking cotton cultivar Xinluzao 13 as test material, a soil column culture expenment was conducted to study the effects of water storage in deeper (> 60 cm) soil layer on the root growth and its relations with the aboveground growth of the cultivar in arid area with drip irrigation under mulch. Two levels of water storage in 60-120 cm soil layer were installed, i. e., well-watered and no watering, and for each, the moisture content in 0-40 cm soil layer during growth period was controlled at two levels, i.e., 70% and 55% of field capacity. It was observed that the total root mass density of the cultivar and its root length density and root activity in 40-120 cm soil layer had significant positive correlations with the aboveground dry mass. When the moisture content in 0-40 cm soil layer during growth season was controlled at 70% of field capacity, the total root mass density under well-watered and no watering had less difference, but the root length density and root activity in 40-120 cm soil layer under well-watered condition increased, which enhanced the water consumption in deeper soil layer, increased the aboveground dry mass, and finally, led to an increased economic yield and higher water use efficiency. When the moisture content in 0-40 cm soil layer during growth season was controlled at 55% of field capacity and the deeper soil layer was well-watered, the root/shoot ratio and root length density in 40-120 cm soil layer and the root activity in 80-120 cm soil layer were higher, the water consumption in deeper soil layer increased, but it was still failed to adequately compensate for the negative effects of water deficit during growth season on the impaired growth of roots and aboveground parts, leading to a significant decrease in the economic yield, as compared with that at 70% of field capacity. Overall, sufficient water storage in deeper soil layer and a sustained soil moisture level of 65% -75% of field capacity during growth period could promote the downward growth of cotton roots, which was essential for achieving water-saving and high-yielding cultivation of cotton with drip irrigation under mulch.