Effects Of Intercropping Stylosanthes As Green Manure On Soil Fertility In Coconut Plantation

To investigate the effect of intercropping of Stylosanthes as green manure on soil fertility of coconut plantation,and to provide theoretical reference support for intercropping of green manure and rational application of green manure in coconut plantation in the acidic soil.Effects of different of Stylosanthes as green manure on the soil fertility of coconut plantation were studied by three-year field experiment,three treatments including of single coconut tree without intercropping with green manure,intercropping Stylosanthes with green manure mulch utilization,intercropping Stylosanthes with green manuring utilization,were designed to observe the dynamics of soil fertility indexes including of soil organic carbon,organic nitrogen fractions,inorganic nitrogen fractions,organic phosphorus fractions,inorganic phosphorus fractions,available potassium,micronutrient,and p H in cultivated soil layer.After three years intercropping,the green manuring and mulch treatments increased the organic matter content by 65.9%and 41.5%,respectively（P<0.05）.Particulate organic carbon,mineral bound organic carbon,recombinant organic carbon and light group organic carbon increased by 584.8%,319.6%,63.1%,45.7%,60.8%,40.7%,227.6%,155.2%,respectively（P<0.05）.Green manuring was effective in increasing soil total nitrogen and organic nitrogen content of each component,with 96.0%increase in soil total nitrogen in the third year,and 121.6%,124.3%,91.6%,102.1,171.7%,and 49.3%（P<0.05）increase in soil acid hydrolyzable organic nitrogen,hydrolyzable ammonia nitrogen,hydrolyzable amino acid nitrogen,hydrolyzable amino sugar nitrogen,hydrolyzable unknown nitrogen,and non-hydrolyzable nitrogen,respectively.In the mulch treatment,total soil nitrogen increased by 55.2%（P<0.05）in the third year,and soil acid hydrolyzable organic nitrogen,hydrolyzable ammonia nitrogen,hydrolyzable amino acid nitrogen,hydrolyzable amino sugar nitrogen,hydrolyzable unknown nitrogen,and non-hydrolyzable nitrogen increased by 71.0%,98.3%,33.4%,54.1%,102.2%,and 26.3%,respectively（P<0.05）.organic nitrogen components were higher under the green manuring treatment compared to the mulch treatment.Both treatments increased the proportion of acid hydrolyzable organic nitrogen and hydrolyzable unknown nitrogen and hydrolyzable ammonia nitrogen to total soil nitrogen and decreased the proportion of non-hydrolyzable nitrogen to total soil nitrogen after intercropping Stylosanthes with green manuring.After three years of intercropping,the green manuring treatment increased NH₄⁺-N and NO₃^--N content by 131.9%and 116.9%（P<0.05）;the mulch treatment increased by 75.7%and 67.3%（P<0.05）.The green manuring and mulch treatments increased the effective phosphorus content by308.0%and 138.0%,respectively（P<0.05）,and increased the inorganic phosphorus content of Al-P,Fe-P,and Ca-P by 403.6%,127.7%;103.6%,36.6%;and 61.7%,18.8%,respectively（P<0.05）.The O-P content was reduced by 47.0%and 30.6%,respectively（P<0.05）.Active O-P,moderately active O-P,and highly stable O-P were elevated by 423.9%,305.5%,and 54.6%,respectively（P<0.05）,and moderately stable O-P was reduced by 31.1%（P<0.05）under the green manuring treatment.Under the mulch treatment,active organophosphorus and medium active organophosphorus increased by 264.0%and 119.7%（P<0.05）,medium stable organophosphorus decreased by 115.5%,and high stable organophosphorus did not change significantly（P>0.05）.The green manuring and mulch treatments increased the contents of fast-acting potassium,slowly available potassium,effective iron,effective manganese,effective zinc,and effective copper by 88.2%,48.7%;24.7%,17.7%;109.5%,67.3%;112.3%,94.8%;34.1%,13.1%（P<0.05）;and 30.1%,21.1%,respectively（P<0.05）.green manuring and treatment also elevated soil p H with increases of 18.1%as well as 14.4%（P<0.05）,respectively.Intercropping of Stylosanthes as green manure could significantly improve soil fertility and soil acidity,and the effect of green manuring was better than that of green manure mulching.