| In northern Henan,the main crop rotation system is annual wheat-maize,which lead to low nitrogen fertilizer and water use efficiency.To solve the problems,two field trials were set up.Test 1: Wheat(W),maize(M),soybean(S),peanut(P)and Spring peanuts(SP)are rotated in six treatments:(1)WM-WM-WM;(2)WM-WS-WM;(3)WM-WP-WM;(4)WP-WP-WP;(5)WS-WS-WS;(6)WM-WM-SP.Test 2: four treatments with different ratios of wheat sowing rate and nitrogen fertilizer were set as:(1)Wheat conventional sowing rate + conventional fertilizer(CBCF);(2)increasing sowing 30% + conventional nitrogen application rate(ZBCF);(3)increasing sowing 30% + reducing nitrogen 20%(ZBJF);(4)conventional sowing Quantity +20% reduction of nitrogen(CBJF).By measuring and analyzing the characteristics of soil nutrients and crop yield changes in different soil layers under different treatments,explore reasonable crop rotation and the technology of sowing rate and nitrogen fertilizer ratio to screen reasonable planting patterns for water and nitrogen conservation and weight loss in northern Henan.The main research results were as follows:Test 1 Different crop rotation modesThere was different effect of additional leguminous crops as peanuts and soybeans in wheat-maize system on soil nutrients and crop yields after one crop rotation cycle.(1)Leguminous crops planted reduced the soil bulk density in 0-20 cm.WP-WP-WP and WS-WS-WS had a significant reduction in 0-20 cm in 2018,reducing 0.20 g·cm-3 and 0.15 g·cm-3,0.18 g·cm-3,0.15 g·cm-3.(2)Compared with the control(WM-WM-WM),WP-WP-WP increased the percentage >0.25 mm agglomerates content in 0-10 cm,about 72%.The average weight diameter(MWD)and geometric average diameter(GMD)were increased,and the fractal dimension(D)was reduced.Compared with the control,WS-WS-WS increased the percentage >0.25 mm agglomerates content in 0-20 cm,which were 64% and 46%,respectively.The MWD and GMD were also improved under WS-WS-WS.(3)In terms of soil nitrogen,Compared with Control,WP-WP-WP and WS-WS-WS increased nitrate nitrogen(NO3--N)and ammonium nitrogen(NH4+-N)in 0-20 cm.In 2019,compared with the control,the soil dissolved organic nitrogen(DON)in 0-10 cm and 20-30 cm soil layers were increased under WP-WP-WP and WS-WS-WS,with the value as 53.83 mg·kg-1,63.28 mg·kg-1,27.11 mg·kg-1,27.59 mg·kg-1,respectively.In 0-20 cm,microbial biomass nitrogen(SMBN)under WP-WP-WP and WS-WS-WS was increased.(4)In terms of soil carbon,WP-WP-WP and WS-WS-WS increased the organic carbon(SOC)content in 0-20 cm soil.WP-WP-WP significantly increased the dissolved organic carbon(DOC)in 0-20 cm in 2019,with 132.06 mg·kg-1 and 116.27 mg·kg-1,respectively.WP-WP-WP and WS-WS-WS significantly improved the soil microbial biomass carbon(SMBC)in 2018 and 2019.(5)In terms of soil available nutrients and enzyme activities,in2018,WP-WP-WP and WS-WS-WS increased the alkali-hydrolyzable nitrogen content(AN)in0-20 cm.In 2019,compared to the control,WM-WM-SP increased the AN;WS-WS-WS reduced the soil available phosphorus content(AP).In 2018,WP-WP-WP increased the available potassium content(AK)in 0-10 cm and 20-30 cm as 172.80 mg·kg-1 and 84.97 mg·kg-1,respectively.In 2019,WS-WS-WS and WM-WM-SP increased soil urease activity,while WP-WP-WP increased soil invertase and neutral phosphatase activity.(6)In terms of soil moisture,in 2018,compared to the control,WS-WS-WS and WP-WP-WP increased the soil field water holding capacity.(7)In terms of crops,the nitrogen harvest index of peanuts and soybeans was significantly higher than that of maize.Planting summer peanuts significantly increased in the phosphorus harvest index.Planting soybeans and peanuts significantly increased the potassium harvest index.After one cycle of all treatments,the wheat yield of WM-WM-SP was slightly higher than other treatments,which was 7358 kg·hm-2.Test 2 Wheat Density Increase and Nitrogen Reduction TestAfter four-year,the results of the next two years show that:(1)The different ratios of sowing rate and fertilizer rate do not change significantly in soil physical indicators.(2)CBCF significantly increased the 0-20 cm NO3--N,NH4+-N,DON,and SMBN content.(3)In terms of soil carbon,compared with the control,ZBCF increased the SOC content in 10-30 cm in 2020(with 10.63g·kg-1 and 9.02 g·kg-1,respectively),and increased DOC.ZBJF increased SMBC in 0-20 cm in two years.(4)In terms of soil available nutrients and enzyme activities,different treatments had little effect on AN and AP.However,compared with the control,ZBJF increased the AK content in 0-20 cm soil in 2019 as 174.02 mg·kg-1 and 89.87 mg·kg-1,respectively.The AK content in0-10 cm in 2020 was also increased as147.53 mg·kg-1.In 2019,CBJF improved soil urease activity and soil neutral phosphatase activity,and CBCF was lower than that under other treatments.In 2020,CBCF increased the urease activity in 0-10 cm,which was 0.79 NH3-N mg·g-1·24h-1.CBJF increased sucrase activity in 0-10 cm as 24.98 Glu mg·g-1·24h-1,and also increased the 0-10 cm neutral phosphatase activity as 7.60 Phenol mg·g-1·24h-1.(5)In terms of soil moisture,in 2020,CBJF increased the field water holding capacity in 0-10 cm,and the nitrogen reduction treatments(ZBJF,CBJF)increased the soil water storage capacity and soil water storage capacity compared to the control.(6)In terms of crops,the increased seeding treatment(ZBCF,ZBJF)increased the phosphorus harvest index in 2019,and CBJF increased the potassium harvest index in 2020.After four years of experiments,it has been shown that nitrogen reduction treatments in 2019 can increase wheat yields to 6292 kg·hm-2 and 6181 kg·hm-2,respectively.By 2020,the number of grains per ear of ZBCF was significantly higher than that of other treatments,and the thousand-grain weight of CBJF treatment was significantly higher than that of the control.Compared with the control,the yield difference of each treatment was not significant.In summary,continuous wheat-peanuts and continuous wheat-soybeans were more conducive to reduce soil bulk density,increase soil nutrient content,and soil biological activity,which was suggested as suitable for local area.Regular sowing and regular fertilizer had a better effect on soil nitrogen,and increased regular fertilizer had a better effect on soil carbon.At the same time,a20% reduction in nitrogen can make wheat yield within four years.Therefore,it was suggested that to increase the amount of wheat sowing rate and reduce the amount of fertilizer. |
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