Study On Effects Of Soil Improvement By Employing Agricultural And Animal Husbandry Wastes

The Zoige Alpine Grassland,located in the transition zone from the Qinghai-Tibet Plateau to the Sichuan Basin,has an important ecological status.However,in recent years,grassland desertification has seriously threatened the ecological security of the region.The typical areas of Zoige county and Hongyuan County in Zoige alpine grassland were selected,and the change characteristics of soil physical and chemical properties in the process of grassland desertification and restoration were described by using typical index analysis method.The effects of agricultural and animal husbandry wastes on the growth of sandy soil and vegetation were quantitatively analyzed.And then,the principal component analysis method was used to comprehensively evaluate the improvement effect of different agricultural wastes on alpine sandy soil.The research results are as follows:(1)Soil desertification characteristics and vegetation control status of alpine grassland in ZoigeSoil desertification causes significant changes in soil organic carbon and aggregate composition.As the degree of desertification increases,the total organic carbon content of the soil decreases significantly.On the one hand,the organic carbon of the agglomerates above 2mm decreases while that of the ones below0.25mm increases.On the other hand,the soil aggregates show a decrease in stability,and the large aggregates transform to micro aggregates.The current situation is that tamarisk planting,the main local vegetation control method,has increased the organic coverage of the surface,but the organic carbon content of the soil does not increase significantly in the early stage of tamarisk planting,and it will increase markedly within 10-15 years.In addition,tamarisk planting significantly increased the content of grain-size aggregates above 2mm in desertified soil,but failed to change the original pattern of sandy soil with grain-size microaggregates below 0.25mm as the main body.(2)Effects of agricultural and animal husbandry wastes on the physical properties of desertified soilThe application of agricultural and animal husbandry wastes can effectively improve the physical properties of the alpine sandy soil.First,in the year of application of wastes,straw and bacterial residue products can increase the moisture content of sandy soil,reduce bulk density,improve agglomeration structure,increase capillary pores and increase field water holding capacity;and the effect is particularly significant in the following year after application(P<0.05).Second,the effects of straw and fungus residue on improving the physical properties of sandy soil will increase over time.The difference is that the amount of application required for the two to achieve the durability of the effect during the experimental monitoring period is different,and the consumption of fungus residue is greater.Furthermore,after the application of agricultural and animal husbandry wastes to the desertified soil,the looseness of the soil and the improvement of the structure will be beneficial to the improvement of the ability of the desertified soil to maintain fertilizer.(3)Effects of agricultural and animal husbandry wastes on the organic carbon pool of desertified soilAgricultural and animal husbandry wastes are rich in organic matter,which can effectively increase the capacity of the organic carbon pool of desertified soil and improve the carbon pool management index.On the one hand,the application of straw to sandy soil made the content of total organic carbon and active organic carbon significant(P<0.05),and the effect increased with the increase of application amount and treatment time.Specifically,in the year of application,the bacterial residue treatment increased the microbial biomass carbon of the sandy soil by 373.27%,and the value reached 1007.03%in the following year.When the straw application rate reached 18 t·hm^-2,the continuous improvement of the carbon pool management index could be guaranteed.On the other hand,the application of agricultural and animal husbandry wastes not only increases the soil organic matter content,but also increases soil active organic carbon reserves.Also,it provides a rich carbon source for soil microorganisms,which has a positive effect on the expansion of the desertified soil organic carbon pool and the improvement of the carbon cycle process.(4)Effects of agricultural and animal husbandry wastes on nutrients and leaching of desertified soilAgricultural and animal husbandry wastes contain a lot of nutrients,which can effectively increase the nutrient content of desertified soil and reduce the leaching rate.First,straw treatment increased the total nitrogen content of sandy soil with time,and the values increased by 56.59%and 78.51%respectively from the beginning to the end of the experimental monitoring period.As for the bacterial residue treatment,the total nitrogen content of the sandy soil increased with the increase of the application amount.After the application amount exceeded 24 t·hm^-2,there was still a tendency to significantly increase the total nitrogen content of sandy soil.In addition,straw and bacterial residue can also significantly reduce the leaching rate of exogenous nutrients in the treatment of high application rate(P<0.05).And then,the application of agricultural and animal husbandry wastes provides rich nutrients for desertified soil and stimulates the rapid development of soil microorganisms.Meanwhile,it can accelerate the degradation of agricultural and animal husbandry wastes while improving the soil structure and the ability to retain fertilizer,thereby reducing the leaching rate of exogenous nutrients and further increasing the soil nutrient content.(5)Effects of agricultural and animal husbandry wastes on vegetation growth in desertified soilThe application of agricultural and livestock wastes promoted the growth of vegetation in desertified soil.For example,the use of straw to treat ryegrass increased the number of seedlings by 18.74%in that year on average,and the value reached 43.11%in the following year,and the survival rate increased with the growth of straw application years;for ryegrass treated with bacterial residue,the plant height increased significantly with the increase of the application amount(P<0.05),and the application amount of 18 t·hm^-2 basically met the requirements for the growth of the plant height.Besides,the chlorophyll content of ryegrass treated with straw and fungus residue increased significantly(P<0.05)with the increase of application years and application amount.Also,both of them had obvious effects on the improvement of root morphology,above-ground biomass and other indicators.In short,adding agricultural and animal husbandry wastes can optimize the structure of desertified soil,alleviate the lack of organic matter and nutrients,and improve the status of water and fertilizer,thereby promoting the growth of vegetation in desertified soil.(6)Contrast of effects of agricultural and animal husbandry waste products on improving alpine desertification grasslandUnder the same application conditions,different agricultural and pastoral wastes have obvious interannual differences in improving water and fertilizer retention capacity and contributing to organic carbon pool.Also,the physiological responses of ryegrass grown in the wild are different.First,in the year of application,biochar has outstanding advantages in soil moisture content,weight on rye grassland and other indicators,while straw has excellent performance in organic carbon pool and nutrients.For other indicators such as bulk density,basic seedlings,root morphology,and chlorophyll,the performance of the three agricultural and livestock waste products are better than cow dung.Second,after one year of application,all indicators of soil organic carbon pool and vegetation growth showed that straw was better than fungus residue,fungus residue was better than biochar,and the biochar was better than cow dung,and the improvement effects of the four products were significantly different(p<0.05).In a word,judging from the effects of soil improvement experiments on alpine sandy land,straw has the best effect,followed by fungus residue,and finally biochar and cow dung.As mentioned above,based on the characteristics of soil desertification and the current situation of sand control by vegetation in Zoige alpine grassland,this paper studies the changes in the nature of desertified soil and the physiological responses of vegetation under the application of agricultural and animal husbandry waste products.The research results show that increasing soil organic matter is the key to the success of sandy soil improvement.In addition,a relationship must be established between the resource utilization of agricultural and animal husbandry wastes and the ecological restoration of alpine deserted grasslands.Most importantly,the research results can provide helpful suggestions for the ecological management of Zoige grassland.