Research On The Soil Fertility Changes Of The Rubber Plantations After Different Stylosanthes Intercropping

Rubber is an important tropical economic crop in China,its planting area is more than 1 million hectares.The soil in hot area usually has many problems,such as low organic matter content,low mineral nutrient content and high acidity.The application of green manure and other organic fertilizers is an important way to solve this problem.Stylosanthes is widely cultivated as green manure in southern China.This paper studied the influence of the Stylosanthes intercropping on the soil fertility of rubber plantation by 5 years positioning experiment.In this experiment,single rubber tree(control),intercropping Reyan No.2,Reyan No.5,Reyan No.7,Reyan No.10,Ubon and Pin125 were established to research the changes of the soil fertility with the respect of the soil nutrients incuding of the diffrent fractions of the soil C,N,P and pH after 5 years intercropping,the main results are as following:The results showed that intercropping of Stylosanthes could significantly increase the yield of rubber and have significant differences between different stylosanthes.RY10 and RY5 were better than others,which increased by 148.2%and 97.0%respectively compared with the control.Intercropping could significantly increase soil organic carbon content.Intercropping could significantly increase soil total organic carbon content and have significant differences between different stylosanthes intercropping.RY5 and Pin 125 were better than others,which increased by 69.9%and 64.3%.Intercropping could significantly affect the content of oxidizable organic carbon in soil In the second year,it showed significant effect and reached the maximum in the fourth year.The content in the fifth year was less than that in the first year,and there were significant differences between different stylosanthes intercropping.RY10 and Pin 125 were better than others,which increased by 364.6%and 119.4%respectively.Intercropping could significantly increase the content of soluble organic carbon and show a significant effect in the second year.There was no significant differences in the last few years.Pinl25 showed better than others,which increased by 84.0%.Intercropping could significantly increase soil nitrogen content.Intercropping could significantly increase soil total nitrogen content and have significant differences between different stylosanthes intercropping.RY5 was better than others,which increased by 177.8%.Intercropping could significantly increase the content of nitrate nitrogen in soil and have significant differences between different stylosanthes.It showed a significant raise in the second year.RY5 was better than others,which increased by 163.3%.Intercropping would significantly reduce ammonium nitrogen in soil and increase nitrate nitrogen.Intercropping could significantly increase acid ammoniacal nitrogen.Intercropping could significantly affect the content of amino acid nitrogen in soil.Intercropping would affect the contents of Al-Pi,Fe-Pi and Ca-Pi in soil and increase the sum of 3 items.RY10 was better than others.Intercropping plants could significantly reduce the content of O-Pi in soil.The upper layer was more sensitive than the lower layer.The content of those components in 0-20cm soil layer were higher than that in 20-40 cm oil layer.Intercropping would reduce soil pH,but after a long period of cultivation,soil pH would increase slightly with a magnitude of 0.1-0.3.The results showed that intercropping stylosanthes could improve soil fertility to prevent soil degradation.