冻融期灌水和覆盖对南疆棉田水热盐的影响

摘要

Scarce water resources and soil salinity are important limiting factors for agricultural production and environmental melioration in extremely drought area and fragile ecological environment of Tarim Basin in southern Xinjiang. The under-film drip irrigation has gained universal applications as an efficient and economically viable irrigation method for increasing water use efficiency and reducing the adverse effects of cotton growth. But for winter and spring irrigation quotas are relatively high and cause groundwater level to rise, after freezing-thawing in winter, salinization occurs on soil surface and it is harmful to the growth and development of cotton seedlings. Soil surface mulching can effectively reduce soil water loss and soil salt accumulation in winter fallow periods, reduce winter and spring irrigation quota, and achieve the purpose of water saving and salinity controlling. To explore the freezing-thawing characteristics in drip irrigation cotton fields under different soil surface mulching and winter irrigation quotas, field experiments were carried out, which included 3 soil surface mulching methods: bare fields (cotton stubble and plastic film were removed before winter irrigation), high stubble fields (cotton stubble and plastic film remained in fields before winter irrigation), corn straw mulching fields (cotton stubble, plastic film remained in fields and mulched corn residue had the length of about 5-10 cm length and the thickness of 5 cm, 400 kg/hm2), and 2 winter irrigation quotas: winter irrigation 200 mm quota and no winter irrigation.Theexperiment was composed of 6 treatments: winter irrigation with bare land (WIB), winter irrigation with high cotton stubble (WICS), winter irrigation with corn straw mulching (WICM), no winter irrigation with bare land (NWIB), no winter irrigation with high cotton stubble (NWICS), and no winter irrigation with corn straw mulching (NWICM). The soil temperatures in 5, 10, 15, 20, 30, 40, 60, 80 and 100 cm were measured; soil water contents and soil salt contents of different soil depth profiles (10, 20, 30, 40, 50, 60, 70, 80, 90 and 100 cm) were measured for different treatments. The field experiments were conducted from November 15th, 2013 to April 4th, 2014 and from November 15th, 2014 to April 4th, 2015. And the results showed that: 1) mulching of soil surface and irrigation could prevent soil temperature from decreasing during soil temperature falling period and play cooling effect during soil temperature rising period; winter irrigation with corn straw mulching could stabilize soil temperature; soil temperature variation in temperature decreasing period was less than soil temperature rising period, and soil temperature variation degree was NWIB > NWICS > NWICM; 2) the freezing index over the experiment periods was bare fields > high cotton stubble fields > corn straw mulching fields under the same winter irrigation quotas; for winter irrigation increased soil moisture, soil heat capacity and soil temperature, the freezing index under WIB, WICS and WICM was 0.35, 29.03 and 41.95℃·d smaller than NWIB, NWICS and NWICM respectively; the thawing index under no winter irrigation was more than winter irrigation treatment under the same soil surface mulching, showing NWIB (300.64℃ ·d) > WIB (292.55℃ ·d), NWICS (256.43℃ ·d) > WICS (239.49℃ ·d), and NWICM (200.82℃ ·d) > WICM (156.80℃ ·d); 3) soil surface with corn straw mulching and winter irrigation was beneficial to maintain soil water during winter fallow period; under the same soil surface, soil moisture storage in 0-100 cm under winter irrigation was higher than no winter irrigation, and under the same winter irrigation quota, soil moisture storage in 0-100 cm under corn straw mulching was higher than cotton stubble and bare fields; WICM moisture storage was 29.10% and 10.36% higher than WIB and WICS respectively, and NWICM moisture storage was 14.97% and 2.21% higher than NWIB and NWICS respectively. After freezing and thawing process, 0-100 cm soil water storage under NWIB, NWICS and NWICM reduced respectively by 18.32, 7.36 and 2.62 mm on average; 4) 0-30 cm soil salt content was arranged as bare fields > high cotton stubble fields > corn straw mulching fields. Winter irrigation with 200 mm could leach soil salt, the leaching effect was corn straw mulching fields > high cotton stubble fields > bare fields, and the leaching rate was 34.86%, 15.82% and 7.26% respectively. Under no winter irrigation, soil salt content was accumulated, and soil salt accumulation rate was bare fields (10.11%) > high cotton stubble fields (7.96%) > corn straw mulching fields (3.01%). The research results can provide important information for the soil water-temperature-salt regulation in winter fallow periods in south Xinjiang.%为了探索不同冬灌定额和地表覆盖模式对棉田水热盐的影响，该文设置了冬灌裸地（winter irrigation with bare land, WIB）、冬灌留秆（winter irrigation with high cotton stubble, WICS）、冬灌玉米秸秆覆盖（winter irrigation with corn straw mulching, WICM）、免冬灌裸地（no winter irrigation with bare land, NWIB）、免冬灌留秆（no winter irrigation with high cotton stubble, NWICS）和免冬灌玉米秸秆覆盖（no winter irrigation with corn straw mulching, NWICM）6个处理。经过2013-11-15－2014-04-04和2014-11-15－2015-04-04冬季大田试验，得到：灌水和地表覆盖可以平抑土壤温度的变幅，免冬灌或冬灌条件下，温度变异幅度均为裸地＞留秆＞玉米秸秆覆盖。玉米秸秆覆盖更有利于土壤水分保持，WICM 土壤储水量比WIB和WICS分别多29.10%和10.36%，NWICM土壤储水量比NWIB和NWICS分别多14.97%和2.21%，经过两年冻融过程NWIB、NWICS和NWICM 0～100 cm土壤储水量平均减少了18.32、7.36和2.62 mm。（免）冬灌0～30 cm土壤含盐量均为裸地＞留秆＞玉米秸秆覆盖；0～100 cm土壤范围冬灌盐分淋洗率为玉米秸秆覆盖（34.86%）＞留秆（15.82%）＞裸地（7.26%）；免冬灌0~100cm积盐率为裸地（10.11%）＞留秆（7.96%）＞玉米秸秆覆盖（3.01%）。研究结果可为南疆冬季休闲期棉田土壤水热盐调控提供科学依据。