| In response to the problems of excessive input of nitrogen,phosphorus,and potassium fertilizers and low fertilizer utilization efficiency in Ningxia Yellow River Irrigation Area(NYRIA),this study explored the effects of reducing fertilizer application for four consecutive years on soil nutrient supply,growth,yield,and quality of spring wheat by analyzing the effects of factors such as soil fertilizer supply,soil moisture before sowing,and climate on yield and quality stability,then providing a theoretical basis for the rational and sustainable reduction of fertilizer application for spring wheat in NYRIA.The main research results are as follows:(1)The results of reducing fertilizer application for four consecutive years showed that the content of mineral nitrogen,available phosphorus,and available potassium in the soil before sowing and during harvest were relatively higher in the conventional fertilization treatment CF,followed by the RF2 treatment;In the 2019 harvest period,there was a varying degree of increase in soil available nutrients compared to that before sowing,with growth rates of 28.02%-42.45%,35.06%-54.97%,and 86.24%-88.49%,respectively.There was no significant difference between CF treatment and RF2 treatment,but there was a significant difference between CF treatment and CK treatment;However,the continuous reduction of fertilizer application resulted in relatively high levels of soil catalase,urease,and alkaline phosphatase under RF2 treatment,and the average enzyme activity increased by 44.12%,12.35%,and 17.74%at harvest in 2019 compared to that before sowing,respectively,with no significant difference compared to the CF treatment.But there were interannual differences.(2)The dry matter in shoot and grain yield were the highest under the CF treatment in 2019,with 23261.67 kg·hm-2 and 9448.99 kg·hm-2,respectively.However,during the 2020-2022 period,dry matter and grain yield of RF2 treatment was the highest,with an increase of 2.82%-4.47%and 3.21%-16.04%,respectively,compared with CF treatment.Although there was no significant difference between RF2 treatment and CF treatment,the grain yield remained stable for 4 years;Meanwhile,except for 2019,the number of panicles per hectare and grains per panicle of RF2 treatment were significantly higher than that of other treatments;The protein,soluble sugar,and starch contents in the grains reached their highest levels in 2019,with protein increased by 10.93%compared to CF treatment under RF2 treatment,soluble sugar increased by 0.78%compared to CF treatment under RF1 treatment,and starch increased by 1.31%compared to RF2 treatment under CF treatment.From 2020 to 2022,the protein,soluble sugar,and starch contents were relatively high under RF2 treatment,followed by CF treatment,and there was no significant difference between the treatments.However,due to the decrease in precipitation,the increase in average temperature,and the acceleration of average wind speed,the yield and quality of spring wheat grains show a decreasing trend year by year,with interannual differences.(3)Reducing fertilizer application was closely related to microbial biomass carbon and nitrogen.Fertilization treatment could significantly increase soil microbial biomass carbon and nitrogen compared to non fertilization treatment;At a depth of 0-20 cm,the soil microbial biomass carbon,nitrogen,and microbial entropy increased by 14.40%,1.10%,and 25.81%,respectively,with the appropriate reduction of fertilizer RF2 compared to the CF treatment;At 20-40 cm,the microbial biomass nitrogen and microbial entropy of CF treatment increased by 17.02%and 17.64%respectively compared to RF2 treatment,but there was no significant difference.(4)Reducing the application of chemical fertilizer RF2 significantly increased the chlorophyll content(SPAD value)and plant height of leaves,increasing by 0.45%and 0.16%respectively compared to CF treatment;Moreover,the photosynthetic characteristics of flag leaves treated with reduced application of chemical fertilizer RF2 were also better than those of conventional fertilization;The stem strength,leaf area index,and stem diameter of spring wheat reached the best under the RF2 treatment level,which increased by 8.48%,17.77%,and 6.08%compared to the conventional fertilization CF treatment,respectively.To some extent,it increased the lodging resistance of spring wheat,thereby promoting its growth and development.The continuous and moderate reduction of chemical fertilizers(N 225 kg·hm-2,P2O5 75 kg·hm-2,K2O 45 kg·hm-2,compared to conventional fertilization,reducing N by 17.0%,P2O5 by 50.0%,and K2O by 40.0%)in NYRIA would not significantly reduce the supply capacity of soil nitrogen,phosphorus,and potassium,and to some extent,it can increase the number of spikes per hectare,grains per spike,and thousand grain weight of spring wheat,promoting the transfer and accumulation of aboveground dry matter mass to grains,thereby tending to improve the grain yield of spring wheat.However,there are interannual differences in spring wheat yield due to climate factors such as rainfall,wind speed,and humidity,as well as soil moisture,continuous cropping obstacles,and nitrogen fertilizer application ratios.Among them,temperature and wind speed are the main factors affecting wheat yield differences,and their impact on fertilization effects needs further research. |
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