Effects Of Different Nitrogen Application Rates On Soil Fertility Of Spring Wheat And Vegetable Double Cropping

In order to study the effect of multiple cropping of three kinds of vegetables after harvest of spring wheat in Ningxia Yellow River irrigation area on soil fertility under different nitrogen application treatments,this study used multiple crops of pepper("Jiaolong No.7")and cabbage("XiaoyiHeqiu")and radish("Xinlimei")are the test materials,and the split plot design is adopted.The main plot contains 3 different vegetables,pepper(A),baby cabbage(B),and radish(C);the sub-plot is Four different nitrogen application levels,N1:0 kg·hm-2、N2:180 kg·hm-2、N3:225 kg·hm-2、N4:270 kg·hm-2.Through the determination of soil physical and chemical properties,soil enzyme activities,soil microorganisms and other related indicators,the comprehensive effects of different nitrogen application rates of three kinds of vegetables on soil fertility were studied,and the suitable vegetable types and corresponding nitrogen application rates for spring wheat post-replanting and soil fertility conservation were screened.The main results are as follows:1.Under different nitrogen application rates,pepper,cabbage and radish had significant effects on soil enzyme activities in 0-40 cm soil layer.During the whole growth period,soil urease,sucrase and alkaline phosphatase activities of the three vegetables increased gradually with the increase of nitrogen application rate,and the values were the highest under N3 treatment.Each treatment increased by 0.8%-47.66%,1.8%-44.67%,0.32%-48.03%;0.11%-28.35%,0.53%-37.38%,2.63%-41.1 6%;0.62-25.77%,0.83%-46.09%,1.12%-58.68%.Soil catalase activity decreased gradually as N1>N2>N3>N4.Compared with N1,catalase activity decreased by 0.26%-15%,0.92%-13.76%and 0.09%-22.83%.2.Pepper,baby cabbage and radish have different trends and effects on soil physical and chemical properties in 0-40 cm soil layer under different nitrogen application rates.Moisture content has a significant effect.With the increase of nitrogen application rate,there was no significant difference in soil bulk density,electrical conductivity and pH value among the treatments.The soil conductivity of different vegetables under the same nitrogen application treatment was as follows:pepper>radish>baby cabbage;pH value was as follows:baby Vegetable>radish>pepper;soil water content and available potassium content gradually decreased,the water content was as follows:N1>N2>N3>N4,and available potassium was as follows:pepper>baby cabbage>radish;total nitrogen,alkaline hydrolyzed nitrogen,total phosphorus,organic matter and fast phosphorus content increased and the value was the largest under N3 treatment,indicating that the appropriate nitrogen application rate has obvious effect on improving soil physical and chemical properties.3.Through the analysis of Alpha and Beta diversity indices,it can be concluded that there are significant differences in the diversity indices of soil bacteria and fungi under different nitrogen fertilization treatments for pepper,baby cabbage,and radish.A total of 44 bacterial communities were detected in the soil samples,and the top 14 bacterial genera groups in the relative abundance of each treatment were similar.Among them,the relative abundance of Protrobacteria was the highest,accounting for 28.08%-22.49%;fungal communities were detected in 14 There were differences in the relative abundance of fungal phyla in each treatment.PCA analysis showed that each treatment could explain 74.84%and 87.02%of the differences in bacterial and fungal composition.The analysis results show that:suitable nitrogen fertilization It can increase the diversity and richness of soil bacteria and fungi.4.Different nitrogen application treatments had different effects on the yield and contribution rate of soil fertility of pepper,cabbage and radish.The maximum yield of pepper and radish under N3 treatment was 1095.19kg/667m2and 6031.31kg/667m2,respectively.With the increase of nitrogen application rate,it showed a gradually increasing trend,which was N4>N3>N2>N1.There were significant differences in the contribution rate of soil fertility among the three vegetables under different nitrogen application treatments.The contribution rate of soil fertility is the largest,and the contribution rate of pepper to soil fertility is higher than that of baby cabbage and radish by 10.58%and 18.37%respectively.The overall performance of the three kinds of vegetables’ contribution rate to soil fertility is:pepper>radish>baby cabbage.5.The correlation analysis of soil fertility index and yield of three vegetables was carried out,and the comprehensive evaluation of soil fertility index showed that urease,sucrase,rapid phosphorus in pepper and radish soil and total nitrogen in cabbage soil had extremely significant positive correlation with yield.The results of principal component analysis showed that N3 treatment had a strong effect on soil fertility improvement,while N1 treatment had the worst effect on soil fertility improvement.The optimal planting mode of pepper was selected,and the optimal nitrogen application rate was 225 kg·hm-2.