黄土高原苜蓿及后茬作物土壤水分恢复效应及蒸散特征

Evapotranspiration and water dynamics of lucerne and following crops in the northwest Loess Plateau

黄土高原种植紫花苜蓿(Medicago sativa)多年后会形成土壤干层,严重影响后茬作物的生长。本研究利用黄土高原建植9年的苜蓿地布设田间试验,研究比较了苜蓿连作(L–L),苜蓿移除后休闲(L–F)或分别种植小麦(Triticum aestivum, L–W)、玉米(Zea mays, L–C)、马铃薯(Solanum tuberosum, L–P)和谷子(Setaria italica, L–M)6种苜蓿-作物种植模式对田间水分蒸散特性的影响及水分动态变化特征。结果表明:苜蓿与作物的轮作中,3年的平均水分利用效率均是苜蓿-马铃薯最高,苜蓿-玉米次之,苜蓿-小麦最低,种植马铃薯和玉米能有效提高作物产量和水分利用效率。苜蓿-玉米处理在高耗水的同时,抑制了土壤棵间蒸发量,显著降低了蒸发与作物耗水量的比率(17.0%),促进了作物的蒸腾作用。经过轮作倒茬后,苜蓿-作物轮作处理下0–300 cm土层的平均含水量较苜蓿连作增加了18.4%～34.9%,苜蓿-休闲处理对于土壤干层水分的恢复效果最佳,其次为苜蓿-马铃薯。综合水分利用效率和农田水分变化特征,在黄土高原半干旱区种植苜蓿多年后选择休闲或轮作其他作物,以苜蓿-马铃薯和苜蓿-玉米轮作的效果较好。该研究结果也表明,合理的利用土地可以减轻土壤干层在黄土高原的形成和发展。

The formation of a dried soil layer after the long-term cultivation of lucerne(Medicago sativa)in the northwest Loess Plateau,China,could seriously affect the growth of subsequent crops.A field study was conducted to investigate the evapotranspiration and water dynamics of crops cultivated after lucerne production.This study involved the following six treatments:lucerne-lucerne(L–L),lucerne-fallow(L–F),lucerne-wheat(Triticum aestivum,L–W),lucerne-corn(Zea mays,L–C),lucerne-potato(Solanum tuberosum,L–P),and lucerne-millet(Setaria italica,L–M).Average water use efficiency(WUE)was greater in the L–P treatment,followed by the L–C treatment,and was the lowest with the L–W treatment after 3 years of continuous production,indicating that 9-year-old lucerne rotated with potato and corn resulted in higher crop WUE than the other treatments.The L–C treatment had the highest water consumption during the crop growing period;however,it had the lowest evaporation among the different treatments,which decreased the percentage of evaporation of crop total water consumption to 17.0% ,which promoted transpiration in the corn crop.Average field water content was increased by 18.4% to 34.9% compared to continuous lucerne in the 0 to 300 cm soil layer depth.The L–F treatment was the best for water restoration among the six treatments,followed by the L–P treatment.Based on the WUE and soil water characteristics,potato and corn are optimal crops for cultivation after lucerne in the northwest Loess Plateau,China.Therefore,optimising land-use management can mitigate the formation of a dried soil layer and assist the development on the northwest Loess Plateau.