Effects Of Continuous Reduction Of Chemical Fertilizer On Growth,Yield And Quality Of Spring Wheat

In view of the widespread excessive application of chemical fertilizer in the production process of spring wheat in the Yellow River irrigation area of Ningxia,which leads to the decrease of fertilizer utilization rate,the increase of agricultural production cost,the instability of wheat yield and quality,and the environmental pollution,this study explored the fertilizer demand law of main spring wheat varieties in Ningxia through pot experiments,in order to provide data support for the reasonable reduction of chemical fertilizer.Through three-year field experiment,the effects of nitrogen,phosphorus and potassium monitoring fertilization and reducing fertilization on soil nitrogen,phosphorus and potassium nutrient supply and spring wheat growth,yield and quality were studied,in order to evaluate the soil fertilizer supply capacity and the sustainability of chemical fertilizer quantitative reduction technology in Ningxia irrigation area,and provide a theoretical basis for chemical fertilizer quantitative reduction and stable yield and quality of spring wheat in Ningxia.The results are as follows:(1)Experimental results on fertilizer requirement and grain quality of spring wheat in Ningxia showed that:The jointing stage and filling stage are the key period of nutrient absorption and operation of spring wheat Ningchun4,Ningchun50and Ningchun55.The average absorption of nitrogen,phosphorus and potassium in Ningchun4accounted for about20%-30%of the total absorption from jointing to heading stage,and about40%-79%of the total absorption from filling to maturity stage.The average absorption of nitrogen,phosphorus and potassium in Ningchun 50 accounts for 30%-40%of the total absorption from jointing stage to heading stage and 50%-70%of the total absorption from filling stage to maturity stage.Ningchun 55 accounted for 35%and 40%-70%respectively.At the same time,at the filling stage and maturity stage,the average contribution rate of nutrients transferred from stems and leaves to grains in the three varieties of spring wheat reached about 50%.(2)The results of the monitoring fertilization experiment showed that:Nitrogen application could significantly increase plant height,aboveground biomass and dry matter accumulation of spring wheat.Compared with no nitrogen fertilizer treatment(PK),nitrogen fertilizer treatment(NPK)increased yield by 40.74%,spike length and grain number per spike by 23.20%and 44.43%,respectively,and soil mineral nitrogen supply increased by 17.3%.The accumulation of nitrogen,phosphorus and potassium in wheat at late growth stage was significantly increased,and the crude protein content in grain was significantly increased by 43.79%.Although the application of phosphorus fertilizer and potassium fertilizer had no significant effect on grain yield,it could significantly improve the aboveground biomass,dry matter accumulation and grain quality of spring wheat,and also increase the accumulation of nitrogen,phosphorus and potassium nutrients in the later stage of wheat growth.During the whole growth and development period of spring wheat,the application of phosphorus fertilizer would increase the supply of soil available phosphorus,and the application of potassium fertilizer would increase the supply of soil available potassium.(3)The results of continuous reduced fertilization experiment showed that:Compared with conventional fertilization(CF),aboveground biomass and dry matter accumulation of spring wheat under reduced fertilization(RF2)were increased.The yields of RF1,RF2 and RF3 under reduced fertilization treatments were significantly higher than those under CK treatment,and both significantly increased the spike number and grain number per spike of spring wheat.The yield of RF2 treatment was the highest,which was 95.66%higher than that of CK treatment.At the same time,RF2 treatment could also significantly improve the nutritional quality of grains,and the crude protein content was 6.32%,33.01%and 9.75%higher than CF,RF1 and RF3,respectively.Continuous application of chemical fertilizer(RF2)can also promote the absorption of nitrogen,phosphorus and potassium nutrients in wheat aboveground,which is beneficial to improve nutrient production efficiency.In summary,the application of nitrogen,phosphorus and potassium fertilizer could significantly improve the ability of soil to supply nitrogen,phosphorus and potassium,but the appropriate reduction of chemical fertilizer could not only maintain the ability of soil to supply fertilizer,but also improve the quality of production.In the Yellow River irrigation area of Ningxia,the application of nitrogen,phosphorus and potassium reduced by 17%,50%and 40%(RF2),respectively,can still promote the accumulation of dry matter in various vegetative organs of spring wheat,and significantly improve spring wheat grain filling-maturity stage aboveground dry matter accumulation,which can delay the senescence of flag leaves to a certain extent,improve the photosynthetic efficiency in the late filling stage,improve the grain filling rate of spring wheat,and also reduce the risk of lodging of spring wheat at filling stage.Promote the transport of dry matter to grain at grain filling stage,reduce the distribution rate of stem,leaf and glume,improve the distribution rate of grain,and increase the number of spikes and grains per spike in spring wheat,thereby improving grain yield.