[Effects of ridge and furrow rain harvesting with supplemental irrigation on winter wheat photosynthetic characteristics, yield and water use efficiency in Guanzhong irrigation district].

A field experiment was conducted to determine the regulation of crop photosynthesis and output and water saving effect under ridge and furrow rain harvesting with supplemental irrigation in Guanzhong irrigation district. The experiment was set with 5 treatments with irrigation at returning green stage, and the widths of both ridge and furrow being 60 cm. T1, T2 and T3 were in the ridge and furrow rain harvesting planting pattern, with the irrigation volumes being 0, 375 and 750 m3 · hm(-2) respectively, T4 was flat planting with irrigation (border irrigation) of 750 m3 · hm(-2) and CK was flat planting without irrigation. Effects on winter wheat photosynthetic organs, photosynthetic rate, yield and water use efficiency, etc. were tested. The results showed that compared with T4, T1, T2 and T3 treatments increased the grain yield by 2.8%, 9.6% and 18.9%, improved the harvest index by 2.0% to 8.5%, advanced the flag leaf chlorophyll content by 41.9% to 64.4% significantly, and improved the 0-40 cm layer soil moisture content by 0.1%-4.6% during the whole growth period. Photosynthetic rates at the flowering and filling stages also increased by 22.3% to 54.2% and -4.3% to 67.2%, respectively. Total water use efficiencies (WUEy) were 17.9%, 10.4% and 15.4% higher than that of T4, and 69.3%, 58.6% and 65.7% higher than that of CK (P < 0.05), respectively, and enhanced precipitation utilization efficiency ( PUE ) by 94.3%-124.5% than CK. Leaf areas of T2 and T3 treatments at each growth stage were significantly higher than that of T4 and CK, irrigation water use efficiencies (IUE) were 119.1% and 18.8% higher than that of T4, respectively. Therefore, it was concluded that ridge and furrow rain harvesting cultivation could maintain higher grain yield than border irrigation without irrigation or with irrigation reduction by 50%. The utilization efficiency of irrigation water under the condition of irrigation reduction by 50% was improved significantly, and the ridge and furrow rain harvesting could significantly improve whole cropland water use efficiency in the year of less rainfall.

[Effects of straw mulching on the soil aggregates in dryland wheat field under no-tillage].

A field experiment was conducted to study the effects of full period and growth period straw mulching with an amount of 3000, 6000, and 9000 kg x hm(-2) on the soil aggregates in a no-tillage dryland wheat field in Weibei Loess Pleateau of Shaanxi Province, taking no full period straw mulching as the control. In the 0-40 cm soil layer, the content of > 5 mm aggregates increased with depth, while that of <5 mm aggregates was in adverse. Under straw mulching, the total contents of > 0.25 mm mechanical stable aggregates (DR0.25) and of > 0.25 mm water stable aggregates (WR0.25) were significantly higher than the control, with an increase of 13.0%-26.4% and 18.6%-45.6%, respectively and the largest increment in the treatment 6000 kg x hm(-2) of straw mulching. Straw mulching increased the soil organic matter content, and the latter had a significant positive correlation with the WR0.25 content. All the straw mulching treatments decreased the soil unstable aggregate index (E(LT)) which was the lowest in treatment 6000 kg x hm(-2) of straw mulching. This study showed that straw mulching could increase the >0.25 mm aggregates and organic matter contents in 0-40 cm soil layer and improve the soil structural stability, and mulching with an amount of 6000 kg x hm(-2) had the best effect, being a reasonable straw mulching mode to be applied in the agricultural production in Weibei Loess Plateau.