不同耕作措施对旱地作物生育期农田耗水结构和水分利用效率的影响

陇中黄土高原旱农区降水有限、水分利用效率低下是导致该区作物生产力水平低而不稳的主要原因。发展保护性耕作是保护水土资源、提高水分利用效率的重要途径。为揭示耕作措施影响水分利用效率的机制,2015—2016年在陇中黄土高原旱农区研究了不同耕作措施对土壤棵间蒸发、农田耗水量、作物蒸腾量、棵间蒸发与蒸散的比例、产量及水分利用效率的影响。试验设置传统耕作(T)、免耕秸秆覆盖(NTS)、免耕(NT)、传统耕作+秸秆翻入(TS)、传统耕作+覆膜(TP)、免耕覆膜(NTP)6个处理,春小麦和豌豆年间轮作。结果表明:(1)春小麦和豌豆全生育期棵间蒸发量NTS、TP、NTP比T显著减少6.52%~50.81%,NTS降低棵间蒸发量的作用主要在小麦开花后和豌豆结荚后,地膜覆盖在各个生育时期基本上都显著减少了棵间蒸发。(2)NTS对全生育期耗水量无显著影响,NTP的耗水量只在小麦地显著高于T。相比T,NTS显著提高了小麦开花-收获和豌豆结荚-收获期间的阶段耗水量及其占总耗水的比例。(3)NTS、TP、NTP均显著提高了春小麦和豌豆的蒸腾量,降低了田间的蒸发占蒸散的比例,降低了水分的无效损耗。(4)各年份春小麦和豌豆的产量NTS、TP、NTP比T提高了7.64%~62.79%,水分利用效率比T提高了0.43%~50.88%。因此,在陇中黄土高原旱农区,免耕秸秆覆盖、地膜覆盖等保护性耕作措施均能提高水分利用效率及小麦和豌豆的产量。免耕秸秆覆盖通过降低作物生长后期棵间蒸发量,提高作物生长后期耗水量,降低蒸发与蒸散的比例,从而提高春小麦和豌豆的水分利用效率及产量。而地膜覆盖处理主要是通过减少全生育期棵间蒸发量,增加作物全生育期蒸腾量,降低蒸发与蒸散的比例,从而实现作物水分高效利用,提高作物产量。

Effects of Different Tillage Practices on Water Consumption Structure and Water Use Efficiency During Crop Growth Period in Arid Farmland

The limited rainfall and low water use efficiency are the main causes of the low and unstable crop productivity in arid agricultural area of the Loess Plateau in Long Zhong. Developing conservation tillage practices is an important way to protect water and soil resources and improve water use efficiency. The aim of the study was to determine the underlying mechanisms of different tillage practices in improving yield and water use efficiency. The effect of different tillage practices on soil evaporation, field water consumption, crop transpiration, ratio of evapotranspiration to evaporation, yield and water use efficiency were studied from 2015 to 2016. The study was conducted in a long-term tillage experimental field located in the arid farmland of Long Zhong. The experiment included six treatments, which were conventional tillage with no straw (T), no-till with straw cover (NTS), no-till with no straw cover (NT), conventional tillage with straw incorporated (TS), conventional tillage with plastic mulch (TP) and no-till with plastic mulch (NTP), all the fields were used for the rotation of spring wheat and pea. The results showed that: (1) Compared with T treatment, the evaporations of spring wheat and field pea in NTS, TP and NTP treatments significantly reduced by 6.52%~50.81% during the whole growth period, and the effect of NTS to reduce the evaporation was mainly after the flowering of wheat and the pod of the pea, and the plastic mulching could significantly reduced the evaporation in each growth period. (2) NTS treatment had no significant effect on water consumption during the whole growth period, and the water consumption in NTS treatment was significantly higher than that in T treatment in wheat fields. Compared with traditional tillage, NTS treatment significantly increased the amount of water consumed and the proportion of total water consumption in the stages of wheat flowering to harvest and pea podding to harvest. (3) NTS, TP and NTP significantly increased the transpiration of spring wheat and pea, reduced effectively the proportion of evaporation to evapotranspiration in the field, and the ineffective loss of water. (4) Compared with T treatment, the yield of spring wheat and pea in NTS, TP and NTP treatment increased by 7.64%~62.79% in each year, and the water use efficiency increased by 0.43%~50.88%. Therefore, the conservation tillage measures, such as no-tillage straw mulching and plastic mulching, could improve the water use efficiency and yield of wheat and pea in the arid agricultural area of the Loess Plateau in Long Zhong. No-till with straw cover could improve the water use efficiency and yield of spring wheat and pea by reducing the evaporation and increasing the water consumption in the later period of crop growth, and reducing the ratio of evaporation to evapotranspiration. The plastic mulching was mainly to reduce the evaporation during the whole growth period, increase the total transpiration of the crop and reduce the proportion of evaporation to evapotranspiration, so as to realize efficient use of water and increase crop yield.