小麦/玉米轮作旱地长期轮耕的保墒增产效应

Soil moisture preservation and improving of crop yield in dry land under long-term wheat/maize rotation

保护性耕作能改善土壤物理结构,蓄水保墒,提高作物产量。但长期采用单一的耕作方式不仅不能促进作物增产,反而会对土壤和生态环境带来一些不利影响。土壤轮耕技术通过合理配置土壤耕作技术措施,将翻、旋、免等土壤耕作措施进行合理的组合与配置,对于减少长期单一耕作缺点具有重要的作用。为探寻适宜于黄土旱塬地区旱作麦玉轮作田长期生产的耕作模式,于2007-2017年在陕西省合阳县设置长期定位试验,该试验共设置4种轮耕模式:免耕/深松轮耕(NS)、深松/翻耕轮耕(SC)、翻耕/免耕轮耕(CN)和连续翻耕处理(CT),分析了不同轮耕模式的土壤物理性质变化、土壤水分利用规律、休闲期土壤蓄水保墒效应及农田增产效应。结果表明,1)轮耕能有效改善土壤结构,降低土壤容重,其中以CN轮耕处理土壤容重较低,0~60 cm土壤容重为1.31 g/cm^3。2)轮耕能在休闲期蓄存更多的土壤水分,其中以CN处理的蓄水效果较好。3)轮耕能在作物生育期为作物提供更好的土壤水分条件,其中以CN处理在冬小麦和春玉米生育期土壤水分状况较好。4)相较于传统翻耕模式,CN模式显著提高作物小麦/玉米轮作田作物产量和水分利用效率(WUE);冬小麦和春玉米平均产量分别为5 221和7 433 kg/hm^2,平均水分利用效率分别为15.5和20.7 kg/(hm^2·mm)。5)不同轮耕处理以CN处理经济投入较低,经济收益较高,2007-2017年平均经济收益为6254元/hm^2。综上所述,从长期可持续发展的角度考虑,CN模式是适宜于黄土旱塬小麦/玉米轮作田的最佳轮耕模式。

Conservation tillage including no tillage and subsoiling with straw mulching can reduce soil disturbance and superfluous evaporation, reserve more soil water and enhance soil fertility, and promote the crop yield. However, applying mono tillage practices in a long term would decrease the crop yield, and bring some defects for the environment and limit the growth of crop. Tillage rotation rotated different soil tillage practices in a rational sequence, and it combined the conventional tillage, rotary tillage, no tillage, and so on. An optimal rotation can alleviate some disadvantages brought by long-term mono tillage. Now the research on tillage rotations mainly focused on rotation of no tillage with subsoiling and short term（2-5 years） tillage experiment. However, the effect of conservation tillage rotation is a long and slow process. And the research on some other tillage rotations was less. To explore the optimal tillage rotation for the winter wheat-spring maize system on Loess Plateau, a long term experiment was conducted in Heyang County, Shaanxi Province from 2007 to 2017. There were 4 tillage rotations in this experiment： rotation of no tillage with subsoiling（NS）, rotation of subsoiling with conventional tillage（SC）, rotation of conventional tillage with no tillage（CN）, and continuous conventional tillage（CT）. The effects of tillage rotations on soil water use and soil water conservation and crop yield increase were detected in 10 years, and there were 5 whole tillage cycles during this experiment. The result showed CN rotation enhanced soil physical property in 10 years, and the soil bulk density of CN rotation was 1.31 g/cm^3 in the soil depth of 0-60 cm. Tillage rotations can reserve more soil water in fallow period, CN rotation was the best one, and the mean soil water storage was 385.8 mm in 10 years. During crop growth season, tillage rotations can provide better soil water condition for crop growth, and CN rotation had better soil water condition during crop growth season in winter wheat-spring maize rotation. Moreover, tillage rotations can increase the crop yield and water use efficiency（WUE） when compared with CT treatment. In 10 years, CN produced higher yield and WUE of winter wheat and spring maize; the average values of crop yield were 5221 and 7433 kg/hm^2, respectively, and the average values of WUE were 15.5 and 20.7 kg/（ hm^2·mm）, respectively. In 2007-2017, CN rotation provided the best economic profit, and the average value was 6254 yuan/hm^2. In 2007, water deficit in key growth season of spring maize limited the crop yield, yield of NS, SC and CT treatments declined significantly, and the economic profits were all in negative values, but CN rotation produced higher crop yield and better economic profit than other tillage treatments. This illustrated that CN rotation was more suitable for the crop production in arid area and dry year. In a comprehensive consideration, the CN rotation enhances the soil property effectively, reserves more soil water and produces higher crop yield, and is the optimal tillage system for the sustainable development of dryland agriculture.