Effects Of Tillage Methods On Red Soil Quality And Maize Growth In Upland

Agricultural management measures are the main factors affecting farmland soil quality and crop growth,in which the tillage methods act on the soil through the mechanical power of the agricultural machinery,thereby changing the soil structure and affecting the fertility supply.With the deepening of research and application of conservation tillage,it was found that the tillage system has obvious regional characteristics due to the influence of soil types and climate.Therefore,soil types are different in different regions.It is of great significance to study different tillage methods on soil quality and crop growth.Red soil is the main soil resource in tropical and subtropical regions of China.Generally,the red soil texture is heavy,the acidity is strong,and the water retention and fertility conservation are poor.The research of the impacts of tillage methods on this soil type needs to be strengthened.In this paper,according to the characteristics of upland red soil in northern Guangdong Province,the field experiment was conducted to study the effects of rotary tillage(RT),rotary tillage + subsoiling(RTSS),subsoiling(SS)and no-tillage(NT)on the quality of red soil and the growth and yield of maize,and the principal component analysis(PCA)method was used to comprehensively evaluate the soil quality.Combined with soil quality index,the paper puts forward a suitable tillage method in the region.The experiment was studied in a randomized complete block design(RCBD)with three replications.The depth of rotation was 20 cm and the depth of deep soil was 40 cm.The main conclusions were as follows:(1)Effects of tillage methods on soil physical characteristics.Compared with NT,RT mainly reduced the soil density in 0-20 cm soil layers,and the RTSS and SS reduced soil density in the entire soil layer(0-40cm),and increased the soil porosity.After harvest,the increased in soil density was measured and there was no significant difference among the treatments,but the soil density in the SS remained the lowest.The variation of soil moisture content was small during the whole period,and the soil moisture content in the SS was the highest after harvest,especially in the 10~30cm soil layer.RT and RTSS reduced 0~20cm depth of soil moisture content.The order of the content of micro-aggregates(<0.25mm)from high to low was RTSS> RT> SS> NT,and the order of mean weight diameter(MWD)was NT> SS> RTSS> RT.RT and RTSS reduced the content of >10mm aggregates,the MWD was low and the stability of soil structure was poor.(2)Effects of tillage methods on soil fertility and microbes.SS and RT increased soil pH value by 0.1~0.3 units compared with other treatments,which helped to slow down soil acidification.NT is conducive to the storage of organic matter and total nitrogen nutrients.The total phosphorus nutrient showed the highest level of SS in all periods,followed by RT and NT,and the lowest is RTSS.The total potassium was evenly distributed in all soil layers,and has little response to the effects of tillage.Both SS and NT have the effect of increasing the soil available nitrogen content.NT is more advantageous for increasing the surface available nitrogen.SS promoted the availability of phosphorus,which had a positive effect on the increase of soil available phosphorus content.After harvest,NT significantly increased the available phosphorus content of the surface layer.SS is conducive to the storage of available potassium,especially after harvest.The surface fertility of RT was better,so the quantity of bacteria,fungi and actinomycetes increased.The quantity of bacteria and actinomycetes in the SS was the highest,but the quantity of fungi was low.NT significantly increased the quantity of fungi.The catalase activity was the lowest in the RTSS,and there was no significant difference among other tillage measures.Urease activity is highest in the SS.(3)Effects of tillage methods on crop growth and yield.Through the determination of the growth conditions of maize at the jointing stage,the big bell stage,the tasseling stage,the silking stage and the milk ripening stage,the plant height value of each growth stage was the largest in the SS,and the RT was the second.There is no difference in stem diameter value between RT and SS,which is higher than NT and RTSS.The order of the leaf area from large to small is RT> SS> RTSS> NT.And NT had a larger decrease in leaf area after the tassel stage.The maize ear traits and yield were measured and found that the number of maize ear grain under SS conditions was the highest,and the 1000-grain weight and yield in the SS were the highest.The number of ear grain and 1000-grain weight in the RT was the second only to SS,and the yield was lower by 3.17% than SS.The 1000-grain weight in the RTSS was significantly lower than SS,and the yield was lower by 5.82% than SS.NT had poor ear traits,and the 1000-grain weight decreased by 9.18% than SS,which resulted in the lowest yield.(4)The comprehensive evaluation of soil quality under different tillage conditions was carried out by PCA.According to the correlation among the indexes,the bulk density,pH value,total nitrogen,available phosphorus,available potassium,acid phosphatase,fungi and actinomycetes were selected as the index of soil quality evaluation.The data was standardized by the membership function to calculate the soil quality index.The soil quality index showed that the SS treatment was the highest,followed by RT and NT,RTSS was the lowest.Combined with maize growth and yield,it is suggested that SS can create good soil structure and fertility conditions,thereby improving land productivity.