Effects Of Seeding Rate And Nitrogen Application On Winter Wheat Yield And Water Use Efficiency Under Straw Mulching On Dry-land

Soil moisture is a major limiting factor for wheat production in the rainfed area in Loess Plateau. Population size and nutrition management can significantly affect wheat growth and water use efficiency. This paper studied effects of population size, nitrogen fertilizer and straw mulching on soil moisture, wheat growth and development, as well as wheat yield and water use efficiency in Weibei Dryland. Field experiment was divided into two parts, one involved seeding rates and population regulation measures, including 10 treatments which were high density with conventional tillage, normal density with conventional tillage, low density with conventional tillage, high density with mulching, normal density with mulching, low density with mulching, high density with root pruning under mulching, high density with defoliation under mulching, normal density with root pruning under mulching, normal density with defoliation under mulching. Another involved N rates and N split-applications, including 8 treatments which were high N rate with one application and normal N rate with one application under conventional tillage, high N rate with one application, high N rate with two applications, high N rate with three applications, normal N rate with one application, normal N rate with two applications and normal N rate with three applications under mulching. The main results obtained were as follows: 1) Straw mulching in fallow period stored 77 mm more water in 0-3m soil profile conventional tillage. Sowing density mainly affects population size before jointing stage, after jointing population sizes were similar. Grain yield was in the range from 5664 to 6533kg/ha, sowing density did not significantly affect wheat production, but compared with normal density and low density treatments, high density treatment reduce harvest index significantly. The yield of high density was significantly higher than that of low density under straw mulch. Compared with conventional tillage, straw mulch reduced wheat yield and harvest index, and increased water consumption, resulting in decreased water use efficiency. Sowing density and straw mulching had no significant interactions.2) Root pruning or defoliation treatment did not affect the 0-3m soil water storage at sowing and at harvest. Wheat grain yield was in the range from 5337 to 6669 kg/ha, water use efficiency ranged from 10.0 to 12.3 kg/ha/mm. Root pruning increased wheat grain yield and harvest index, and improve water use efficiency; there’s a trend to reduce the yield and water use efficiency under the defoliation treatment. 3) Nitrogen rates did not affect the SPAD value in studied wet year. And basically N rates had no significant effect on photosynthetic rate, transpiration rate and soluble protein and MDA contents of flag leaves. Both straw mulching and nitrogen split applications did not have a significant impact on physiological characteristics of flag leaf. Nitrogen rates and nitrogen split applications had no significant effects on grain filling rate, yield and yield components. Grain yield varied from 5562 to5861 kg/ha.Based on the above results, in wet year of dry-land area in Loess Plateau, seeding density did not significantly affect winter wheat yield and its components. Straw mulch reduces wheat yields and harvest index relative to conventional tillage. Root pruning increased wheat grain yield and harvest index under straw mulch, and increased water use efficiency. Nitrogen rates and straw mulching did not significantly affect physiological characteristics of flag leaves and wheat yield. Therefore, the interactions between seeding density, straw mulch and nitrogen need further research in other climatic conditions to comprehensively evaluate the impact of these factors.