Screening Of Fertilization Methods To Improve Protein Concentration Of Winter Wheat In Plastic-mulched Fields

The Northwest dryland is a typical rainfed dry farming area in China.Uneven precipitation distribution and insufficient rainwater management are the main limiting factors for crop production in this region.Plastic film mulch（PM）system is widely used in dryland because it provides a conducive soil hydrothermal condition to crop yield.However,the current fertilizer application method（PM1;ridging after fertilizers broadcast application）had negative impacts on grain protein concentration of wheat due to insufficient supply of soil water and nitrogen（N）after anthesis.Optimizing fertilizer application ways has been considered as an effective way to overcome the current wheat production challenges.Although there have been many studies for the effects of optimizing N management on crop quality in recent years.However,few studies have focused on the coupling of spatial distribution of soil water and nutrient in order to improve grain yield and protein formation for film mulching of winter wheat.Therefore,a field experiment was conducted to research the effects of optimizing fertilization ways on the spatial distribution and dynamic changes of soil water and nutrition after anthesis.And based on ¹⁵N-labeled method,we explored the contributions of plant N uptake and apparent N remobilization to grain N accumulation at post-anthesis.The main results were as follows:（1）Optimizing fertilizer application ways to improve wheat yield and grain protein concentration.The main reason for PM1 to reduce grain protein concentration by 8%was found to decrease gliadin concentration at 14-48 days after flowering（DAF）by 7%–14%.Compared with PM1,PM3（fertilizers striped application on the side of seed and under the ridge）increased grain yield and protein concentration by 5%and9%,respectively.PM3 increased gliadin concentration by 11%–60%at 21-48 DAF.Therefore,optimizing N fertilizer management can provide potential opportunities for simultaneous improvement of crop yield and grain quality.（2）Improving plant N uptake and remobilization by optimizing fertilizer application ways.It was found that the difference of grain total N accumulation of winter wheat was mainly due to chemical N fertilizer.PM3 increased the contribution N supply from ¹⁵N-labeled fertilizer to grain N accumulation by 51-89%,and increased shoot N uptake from ¹⁵N-labeled fertilizer by 39%,71%and55%at 14,28 and 48 DAF,respectively.On average,apparent N remobilization from shoot contributed 39-56%of grain N accumulation at harvest stage.However,the difference in grain N accumulation of PM systems mainly came from plant N uptake after flowering.PM3 promoted direct distribution of N uptake from plant to grain through increasing plant N uptake by 7%–17%after anthesis,further increased total N uptake of grain by 29%,16%and 15%at14,28 and 48 DAF,respectively.Our results clearly showed that the dynamic absorbing and remobilizing manner of fertilizer N and soil N after wheat flowering was not the same,i.e.,optimized N application way increased the apparent remobilization of fertilizer N,but it did not affect the apparent remobilization of total N.（3）Improving the supply of ¹⁵N-labeled fertilizer and water by optimizing fertilizer application ways after anthesis.Compared with PM1,PM3 increased soil water storage in Wheat Rows and furrows of 10–20 cm soil layer by 11%and 12%,respectively.The spatial distribution of N in soil was regulated by N fertilizer application ways and soil hydrothermal condition,which affected the absorption and utilization of N after anthesis.PM3 reduced NO₃-N accumulation of Ridge in 0–10 cm soil layer by 73%and 83%at anthesis and harvest stage,respectively.PM3 increased NO₃-N accumulation of Wheat Rows in 0-10 cm soil layer by 94%at anthesis stage.PM3 increased N supply from ¹⁵N-labeled fertilizer in Wheat Rows of 0-20 cm soil layer by 146%,thus increased the contribution of N fertilizer to grain N accumulation.In conclusion,optimizing fertilizer application ways can improve the spatial distribution of soil water and nutrient of winter wheat after anthesis in plastic film mulch system,which is beneficial to tap the potential of soil water and nitrogen utilization under the ridge,improve the contribution N supply from fertilizer,promote plant N uptake and grain N accumulation at harvest stage to increase grain protein concentration.Therefore,such improved measure can promote crop yield,ensure grain quality and provide a reference for facing the limitation of wheat production in dryland agriculture.