Research On Agroforestry Systems Of Rubber Plantation

From April 2005 to October 2006, Marus migriformis Koidz, Paspalum atratum, Stylosanthes guianensis were intercropped in 3 years'rubber plantations of Rubber Institute's third experimental field of South China University of Tropical Agriculture. Marus migriformis Koidz was intercropped in 6 years'and 25 years'rubber plantations and corresponding control experiment was planed. The main ecological factors of rubber plantations of this intercropping system was studied, and agroforestry ecosystem's ecological benefit; economic efficiency ; social benefit were comprehensively evaluated. The results showed that:1 The agroforestry ecosystem can make use of the solar energy effectively, and increase the total photosynthesis areas and times to increase the total solar energy utilization efficiency. After intercropping in rubber plantation, the net photosynthetic rate and solar energy utilization efficiency have not got any obvious difference between intercropping areas and control experiment, but net photosynthetic rate of intercropping plants themselves (Marus migriformis Koidz, Stylosanthes guianensis) have obvious difference with control area's(grassland plantation).2 Intercropping rubber plantations of the agroforestry ecosystem can reduce photosynthetic available radiation, with the largest extent taken by 25 years'rubber plantations, second largest taken by 6 years'rubber plantations, and with the least taken by 3 years'rubber plantations. During the experiment, the reduction of photosynthetic available radiation has no obvious influence on rubbers, but impacts intercropping plants to a certain extent. The growth condition of intercropping plants of 25 years'rubber plantations is weakest3 The agroforestry ecosystem can reduce atmosphere temperatures. In different months of the year, the intercropping areas in 3 years'rubber plantations were 0.5~2℃lower than control areas. The 6 years'rubber plantations were 0.6～1.5℃and the 25 years'rubber ones were 0.3~1℃. In the seasons with high temperature, the temperature reduction extent of intercropping plantation is obvious. There is 3.5℃-reduction in 3 years'rubber plantations; the 6 years'and 25 years'respectively are separately 2.3℃and 1.8℃. The 3 years'rubber plantations have most katabatic extent, the 6 years'rubber plantations take second place, the 25 years'rubber plantations have the least. The atmosphere temperature reduction is beneficial to the growth of rubbers and intercropping crops.4 The agroforestry ecosystem can raise atmosphere relative humidity. In different months of the year, the intercropping areas in 3 years'rubber plantations are 3～5% higher than control areas, the 6 years'rubber plantations were 2.1～4.5% and the 25 years'rubber plantations were 2.8～6.5% higher than the control areas. In midsummer with high temperature, the humidity increased extent of intercropping area is obvious. There are 8%, 6.5% and 8.3% of humidity increase separately in 3, 6, 25 years'rubber plantations. The air relative humidity increased is beneficial to the growth of latex flow of rubber.5 The agroforestry ecosystem can reduce the soil temperatures of surface layer. 0cm, 5cm, 10cm, 15cm under the surface layer, their reducing extent are separately 1.8~2.9℃,1.0~2.8℃,1.1~2.7℃,0.4~0.9℃in 3 years'rubber plantations, 0.8~1.8℃,0.7~2.8℃,0.3~1.8℃,0.4~0.6℃in 6years'rubber plantations, 0.6~1.2℃,0.5~1.0℃,0.2~0.6℃,0.4~0.6℃in 25years'rubber plantations. The soil temperature reduction of surface layer in the intercropping systems is beneficial to the growth of rubbers and intercropping plants, and the reduction of harm to rubber root in summer or dry seasons.6 The agroforestry ecosystem can improve the soil nutrient content of available P, but the other content of soil O.M., total N and available K were lower. The reason may be for lake of prompt fertilization during the intercropping process, the crops need absorb nutrient from soil constantly and take more nutrient (N/P/K)from soil when the intercropping plants growth . Thereby this results in deduction of soil O.M. ,total N and available K. Besides, the soil of available K is easily lost when raining. The soil of available P is higher after intercropping because the soil's solid P is released continually. So that it must add the dosage of fertilizations timely were beneficial to the growth of rubber and intercropping crops.7 The agroforestry ecosystem can increase the water content of soil and reduce soil pH. The increased extent of soil water content is 0.04~2.46% in 3 years'rubber plantation, 1.44~2.26% in 6 years'rubber plantation and 1.26~3.13% in 25 years'rubber plantation. The pH is in the range of 4.5~5.5 which is suitable to the growth of rubber trees after intercropping.8 The agroforestry ecosystem can promote rubber growth. The growth of rubber trees is faster than that of control area. The extent of intercropping Marus migriformis Koidz and Paspalum atratum and Stylosanthes guianensis are 7.37%,6.89%,4.45% faster in 3 years'rubber plantations. The 6 years'rubber plantations are 8.46% faster than control area.9 The agroforestry ecosystem can promote the holistic economic benefit of rubber plantations. The 3 years'rubber plantations'income increases 37. 6% after intercropping migriformis Koidz; it increase 58.1% after intercropping Paspalum atratum; and 27.4% income after intercropping Stylosanthes guianensis. The 6 years'rubber plantations increases 35.2% income after intercropping migriformis Koidz. And 25 years'rubber plantations'income increases 11.9% after intercropping migriformis Koidz.