不同生育期土壤基质势调控对棉花生长和土壤水盐分布的影响

针对南疆地区水资源短缺和棉田土壤盐碱化问题,研究不同生育期土壤基质势调控对棉花生长和土壤水盐的影响,为棉田节水控盐和高效生产提供理论依据。通过大田膜下滴灌试验,以棉花灌水时期滴头下方20 cm处土壤基质势下限控制水平-50 kPa为对照(CK),在棉花的苗期(A)、苗期+蕾期(B)、苗期+蕾期+花铃期(C)设置3个基于土壤基质势下限的灌溉水平:W₁(-20 kPa)、W₂(-30 kPa)和W₃(-40 kPa),测定棉花生长、地上干物质量、产量和土壤水盐分布等指标。结果表明:不同生育期土壤基质势调控时,株高、叶面积指数和地上干物质量均表现为:WC>WB>WA>CK;不同土壤基质势水平调控时,随着土壤基质势下限的提高,株高、叶面积指数和地上干物质量也随之增加,其中,W₁C和W₂C处理显著高于其他处理。有效铃数、单铃重和衣分等产量构成要素均随着土壤基质势下限的升高而增加。W₁C和W₂C处理棉花的产量基本一致且显著高于其他处理,W₂C的水分利用效率显著高于W₁C处理。不同生育期土壤基质势均控制在-20或-30 kPa可以改善棉花主根区水分状况。各处理在收获期均表现为浅层积盐(0～40 cm),且膜外大于膜内;土壤基质势越高,膜内主根区(0～40 cm)积盐越少,其中W₁C和W₂C较其他处理减少24%。综合考虑高效生产和节水控盐,建议将当地休作期未淋洗棉田灌水时期土壤基质势控制在-30 kPa为宜。

Effects of soil matrix potential regulation at various growth states on cotton growth and soil water and salt distribution

Water shortage and soil salinization are two main limiting factors for cotton production in southern Xinjiang.We examined the effects of soil matrix potential(SMP)regulation at various growth stages on cotton growth,soil water and salt distribution,to provide theoretical basis for water saving,salts control,and efficient production in cotton fields.The mulched drip irrigation experiments were conducted to monitor cotton growth,aboveground biomass,cotton yield,soil water and salt distribution and other indicators.Three SMP thresholds,i.e.,W1(-20 kPa),W2(-30 kPa)and W3(-40 kPa)were set at the seedling stage(A),seedling stage+budding stage(B),and seedling stage+budding stage+flowering stage(C),with SMP of-50 kPa at 20 cm soil depth below the emitter as the CK.The results showed that plant height,leaf area index(LAI)and aboveground biomass followed the order of WC>WB>WA>CK,when SMP were changed at various growth stages.Plant height,LAI and aboveground biomass increased with increasing SMP thresholds,with the values under W1C and W2C being significantly higher than the other treatments.The effective bolls per plant,single boll weight and lint percentage all increased with the increases of SMP thresholds.The yields of W1C and W2C were similar,which were significantly higher than those of other treatments.However,the water use efficiency of W2C was significantly higher than that of W1C.Controlling the SMP threshold at-20 or-30 kPa at different growth stages could improve soil moisture status of the primary cotton root zone.All treatments presented shallow salt accumulation(0-40 cm)at the harvest stage,with the bare land having greater salt accumulation than the inner film.The higher the SMP threshold was,the less salt was accumulated in the primary root zone(0-40 cm)under film.The salt accumulation(0-40 cm)under W1C and W2C were reduced by 24%compared with other treatments.Considering the efficient production of cotton,water saving and salt control,it was recommended to maintain the SMP threshold of-30 kPa during irrigation at various growth stages in cotton fields without leaching salts during the local off-crop period.