Effect Of Conservation Management On Red Soil Fertility And Maize Yield

Conservation management,including organic fertilizer application,crop straw coverage and no tillage technology,can not only promote soil nutrient availability and improve soil structure,but also promote soil biological community and increase crop yield.The soil nutrient,microbial community and enzyme activity are important indicators of soil fertility level.Red soil is located in hilly regions which is vulnerable to erosion,and can seriously endanger the sustainable development of agricultural ecosystem.Currently,few integrated studies have explored the effects of conservation management on the biophysical properties integrating soil nutrients,microbial community and enzyme activity in various aggregates.Moreover,the short-term effects of field conservation management referring to no-till and organic amendment type on soil fertility and crop yield was still a knowledge gap-This thesis included two paralleled field experiments.First one aimed to investigate the effect of long-term application of organic amendment(pig manure)and chemical fertilizer on soil fertility and maize yield,including no fertilizer treatment(CK),chemical fertilizer(NPK),manure(OM),chemical and manure(NPKM).The experiment would demonstrate the influence of organic and chemical fertilizers on soil nutrients,microbial community structure and enzyme activity,especially changes of nutrients,microbial community and enzyme activity in different size of soil aggregate.The results were as follows:1)Long-term application of manure could significantly increase soil nutrient content(p<0.05),promote soil microbial biomass,reduce C:P ratio,N:P ratio and G+:G-bacteria ratio(p<0.05),and also increase the activity of most enzyme activities,while phosphatase activity was the highest in the NPK treatment(p<0.05).2)The application of manure could promote the formation of>2 mm aggregates and soil structure stability.The order of Mean Weight Diameter(MWD)values in different treatment was as followed,OM>NPKM>CK>NPK.3)Long-term application of manure facilitate soil nutrients and soil enzyme activities,participating in soil carbon cycle,to smaller aggregates(2-0.25 mm,<0.25 mm),but the various microbial biomass is more concentrated in medium aggregate(2-0.25 mm).The second experiment,based on the short-term effects of different organic materials(pig manure,straw cover)with no tillage management on soil fertility and maize yield,investigated the response of soil chemical properties in two soil layers(0-10 cm and 10-20 cm)and maize yield in different tillage system in continuous 3 years.The results are as follows:1)In 0-10cm soil layer,comparing to treatments without manure,soil pH tended to increase and especially reached a significant level in manure treatments at the third year(p<0.05).The treatment including straw cover,manure with no-till had a highest soil pH value.Soil EC also had the same trend.2)In 0-10cm soil layer,total carbon(SOC)in straw cover with no-till treatment was significantly higher than that of conventional tillage treatment from the second year(p<0.05).Application of manure had a significant effect on soil total nitrogen(TN)in late maize of the first and third year(p<0.05),the treatment including straw cover,manure with no-till was the largest and was significantly higher than no-tillage(p<0.05).Manure can significantly increase total phosphorus(TP)from the second year(p<0.05).3)In 0-10cm soil layer,manure application significantly increased soil avaible P(AP)in late maize every year(p<0.05).Straw cover application had a higher content of soil avaible K(AK)than without straw cover applicaiton.Overall,soil AK content was the highest in the treatments including straw cover,manure with conventional tillage and was significantly higher than conventional tillage without straw cover and manure treatment(p<0.05).4)In 10-20cm soil layer,there were no significant effects of straw cover,manure,tillage and their interactions on pH,SOC,TN,TP.And manure has the tendency to increase soil EC in late maize every year.Comparing with the conventional tillage,no-till had a tendency to decrease NO3--N,mineral N,especially in second and third year.However,Straw cover significantly affected AK in 10-20 cm soil in late corn of second and third year.After the second year,soil pH of depth to 10 cm was lower than 10-20 cm.And other chemical properties have larger values in the 0-10 cm soil than 10-20 cm soil.5)Straw cover mainly influenced maize yield in the late maize of second and third year.Moreover,maize yield in straw cover treatments was higher than without straw multching treatments.In summary,the responses of different conservation management and sampling time on soil fertility and crop yield were various.The long-term experiment showed that organic fertilizer combined with chemical fertilizer treatment may be the best way to improve soil fertility and maize yield.The 3 years short-term experiment illuminated that,the application of organic manure combined with different tillage management on soil fertility and maize yield effect has not fully displayed,on the whole,three years of application of organic materials mainly improve the soil available nutrient content and yield of maize.