| Water scarcity and poor soil fertility are two major restricting factors affecting northwest dryland farming. Straw returning can increase soil fertility, improve soil quality, regulate nutrient supply, conservate water, and increase crop yield. Green manure is the soil-improving crop, which not only increases soil fertility, but also improves the soil quality. Therefore, using different cultivation methods of dryland farming, especially straw returning and green manure planting, are the efficient options to resolve the drought and problem of poor soil fertility in the northwest area of China. With bare fallow in summer as control, field experiments were carried out to study influences of wheat straw returning, green manure planting and their mixture under no-tillage on winter wheat yield, contents of soil water and available nutrents, water use efficiency and uptake of nutrents by winter wheat, the accumulation and translocation of nutrients on dryland of the Loess Plateau, China. The main objective of this study was to evaluate the effects of different cultivation methods, and provide theoretical supports for improving soil fertility and productivity on dryland of the Loess Plateau. The main results were as follows:1.After one-year of field experiment, obtained results showed that straw returning and green manure planting in summer fallow period had no effect on the winter wheat yield and biomass. Planting green manure and straw+green manure decreased water storage in 60-160 cm soil layers in stages of pre-seeding and flowering. Compared with the control, planting green manure significantly increased soil nitrate-N in 0-20 cm soil layer by 10.7 kg·hm-2 at pre-seeding and 18.4 kg·hm-2 at harvest. At flowering stage, planting green manure enhanced the amount of available P in surface soil by 43.4 kg·hm-2 and 24.4 kg·hm-2 at harvest. However, straw returning and planting green manure had no significant effect on soil ammonium-N and available K.2. Straw returning in summer fallow period increased water consumption of winter wheat while planting green manure and their mixture treatments decreased it. Compared with the control, straw returning increased it by 10 mm while planting green manure and their mixture decreased it by 11 mm and 9 mm. However, straw returning and planting green manure had no significant effect on water use efficiency. Additionally, planting green manure and straw returning plus planting green manure in summer fallow period significantly declined nutrient uptake by winter wheat with N uptake by 6.0% and 6.6%, P by 5.9% and 6.2%, and K 7.9 % and 7.9%, respectively.3. Straw returning and green manure planting in summer fallow period had increased the amount of pre-anthesis accumulation of dry matter and N,P,K nutrients to different extends, straw returning > straw returning plus planting green manure> planting green manure > the control. Compared with the control, straw returning significantly increased the amount of pre-anthesis accumulation by 25.4%. Additionally, straw returning, planting green manure and straw returning plus planting green manure in summer fallow period increased the amount of pre-anthesis nutrient accumulation by winter wheat with N accumulation by 34.2%,13.4% and 20.9%, P by 31.3%,7.2% and 21.7%, and K by 28.9%,12.2% and 18.3%, respectively. The nutrient accumulation caused by straw returning and straw returning plus planting green manure treatments were significant at P≤5%. In terms of the amount of post-anthesis dry matter accumulation, straw returning, green manure planting and their mixture treatments significantly decreased it by 65.2%, 49.2% and 47.2%, respectively. No obvious post-anthesis N and P accumulation was observed for the three soil surface returning treatments, while K was found to be lost after flowering compared to the control. |
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