| At present,the soil organic carbon content of arable land in Inner Mongolia decreases year by year,resulting in a serious decrease in the water and fertilizer retention capacity of the soil in the cultivation layer,while the river-loop irrigation area is the main grain-producing area in Inner Mongolia,which is subject to diffuse irrigation by the Yellow River water all year round,and the soil organic carbon content is even lower,and it is mostly saline.Therefore,this experiment was conducted on mildly alkaline soils in the river-loop irrigation area,with five treatments of biochar(BC),cow dung(CD),goat manure(GM),straw(SW)and control(CK)in the field from 2019 to 2020.The experiment was added in spring each year,and the addition standard was the full amount of straw returned to the field(10.5 t/ha),the amount of organic carbon(2.4 t/ha)added.The effects of different organic materials on the organic carbon pool,chemical properties,physical characteristics and enzymatic activities of alkalized soils under equal organic carbon addition patterns were analyzed.On this basis,the fuzzy evaluation method of soil quality was applied to further evaluate the quality of the soil,so as to screen out the organic material addition mode suitable for application in the alkaline soil of the river-loop irrigation area,and provide feasible suggestions and scientific basis for future improvement of the quality of alkaline soil and rationalization of organic material resources utilization.The results of this study indicated that:(1)In terms of carbon storage of alkalized soil,organic matter addition can increase the organic carbon content of alkalized soil,among which the organic carbon content of0-30 cm soil layer is most significantly increased.Through the two-year experiment,the organic carbon content of soil treated with biochar and cow dung increased by 27.1% and47.4% compared with CK(P<0.05),while the organic carbon density of soil treated with biochar,cow dung and goat manure also The organic carbon density of soil treated with biochar,cow manure and sheep manure also increased by 30.9%,52.3% and 13.8%compared to CK(P<0.05).The organic carbon fractions under different organic matter additions were different,with cattle manure and sheep manure contributing 55.3% and41.6%(P<0.05)more to the soil organic carbon pool than CK,while biochar contributed82.5%(P<0.05)more to the soil organic carbon pool than CK,mainly with hard-to-oxidize organic carbon.The analysis of soil organic carbon oxidation stability coefficient showed that straw and cow dung were more favorable to improve the stability of organic carbon in alkalized soil and the accumulation and preservation of organic carbon in alkalized soil.(2)As for the salinity of alkalized soil,the addition of organic matter could reduce the p H of alkalized soil.By the end of 2020,the p H of 0-30 cm soil layer in biochar,cow manure,sheep manure and straw treatments decreased by 0.38,0.21,0.27 and 0.24,respectively,compared with the control(P<0.05),and the p H of each treatment in 30-60 cm soil layer decreased by,biochar: 0.26,cow manure: 0.11,sheep manure: 0.18 and straw: 0.18(P<0.05).The ESP of biochar and cow manure treated 0-30 cm soil layer decreased by 36.9% and 29.3% compared to the control(P<0.05),where biochar also inhibited the return of salt to the alkalized soil,and the EC value decreased by 36.3%compared to the control(P<0.05).(3)In terms of alkalized soil nutrients,cattle manure and sheep manure significantly increased alkalized soil nutrients,with 45.2% and 8.8%(P<0.05)increase in fast-acting potassium and total nitrogen content in cattle manure treatment compared with the control in the 0-30 cm soil layer,29.6%(P<0.05)increase in total nitrogen content in sheep manure treatment compared with the control,and 35.6% and 35.6%(P<0.05)increase in fast-acting phosphorus and fast-acting potassium content in cattle manure treatment compared with the control in the 30-60 cm soil layer.(P<0.05),and 39.1% and 32.1%(P<0.05)for fast-acting phosphorus and fast-acting potassium in the sheep manure treatment compared with the control.(4)Regarding the physical properties of alkalized soil,cow manure significantly improved the water holding capacity of alkalized soil,and there was no significant difference in the surface soil capacity of each treatment because the irrigation method was diffuse irrigation with Yellow River water,while the capacity of each organic matter treatment in the 30-60 cm soil layer decreased,among which biochar and sheep manure treatments decreased significantly by 5.6% and 8.9% compared with CK(P<0.05).However,each organic matter treatment increased as the percentage of water-stable agglomerates became smaller in diameter and increased,with 158.05%,357.45% and77.62%(P<0.05)more water-stable agglomerates larger than 2 mm in cattle manure,sheep manure and straw treatments compared to CK,while 0.25-2 mm water-stable agglomerates in cattle manure and straw treatments increased by 81.51% and 83.01%(P<0.05).(5)Regarding alkalized soil quality and crop yield,the yield could not be compared between annual seasons because of the different varieties of maize planted in two years,but the above-ground biomass and crop yield of cattle manure treatment performed best until the autumn harvest of 2020,and the SQI(Soil quality index)index of cattle manure treatment was the largest,and the alkalized soil quality increased by 30.5%(P<0.05),that is best soil quality.In conclusion,different organic materials play different roles in the nature of mildly alkaline soils in the river-loop irrigation area,but cow manure has a high agricultural use value due to its actual application cost and use effect on both crop yield and and soil quality,and can provide a good guarantee and ground strength basis for subsequent soil production. |
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