[Regulation effects of irrigation methods and nitrogen application on soil water, nitrate, and wheat growth and...

Field experiments were conducted to examine the effects of flooding irrigation (FI), micro-sprinkler irrigation (SI), drip irrigation (DI), combined with nitrogen application (N₁:157.5 kg·hm^-2 as basal, 67.5 kg·hm^-2 top dressed at jointing stage; N₂:157.5 kg·hm^-2 as ba-sal, 45 kg·hm^-2 and 22.5 kg·hm^-2 top dressed at jointing stage and filling stage, respectively) on soil moisture, nitrate (NO₃^--N) content, and wheat growth and development, under maize straw returning to field. Results showed that irrigation methods and nitrogen application modes affected soil water content and soil water storage (SWS). Irrigation methods had limited effect on soil water content in the 0-60 cm soil depth at the wintering and re-greening stages, 0-160 cm soil depth at the booting and filling stages, 100-160 cm soil depth at the mature stage, but had substantial effect on water content in the 80-160 cm soil depth at the wintering and re-greening stages, 0-80 cm soil depth at the mature stage. The effects of irrigation methods on water content and SWS were in the order of FI>DI>SI. Under SI and DI, water content, SWS of soil layers, and their changes increased with increasing irrigation rate. Nitrogen application had obvious effect on NO₃^--N content in the 0-20 cm soil depth. In the SI, variation of NO₃^--N content among different growth stages was evident. In the DI, changes of NO₃^--N content were non-evident during wintering and booting stages, and were evident after booting stage, with opposite change treand in the FI. In general, NO₃^--N content was influenced by irrigation rate at early and middle stages of wheat growth, but was mainly affected by N application at late stage. In the SI and DI, NO₃^--N content changed larger by irrigation rate before winter. Total stem number and tillers per plant during overwintering period, panicle number rate, panicle number, yield, WUE and nitrogen use efficiency (NUE) were in the order of SI>DI>FI. In the SI and DI, total stem number and panicle number were higher in the N₁ than that in the N₂, but grain number per panicle, 1000-grain mass, yield, WUE and NUE were lower. Sowing wheat after maize straw returning to the field, replacing FI with micro-sprinkler irrigation four times during the wheat growth period, applying sufficient basal fertilizer and then topdressing at jointing and filling stages, are the high-efficiency and water-saving cultivation strategies of wheat in wheat-maize double cropping area in southern Shanxi.