| Natural rubber production provides an important industrial raw materials and strategic materials for China.Hainan is an important natural rubber producing area in China.But the scale of planting was also accompanied by many problems in the ecological environment,such as irrational land use and fertilization methods,super high and super steep slope planting,not according to the procedures for the construction of mountains,serious damage to the protective forest system,which had caused more serious forest land degradation,soil acid and alkali imbalance,soil and water loss,the decline in production capacity and other issues.By "space replacement time" method,the research about soil nutrient and soil and water conservation of rubber plantations at different ages in five areas in Hainan showed that there was a big difference between the ages of various rubber trees on fertilizer and water demand,and mainly manifested in the following aspects:(1)Changes of soil nutrients in rubber plantation.In general,the distribution pattern of soil organic matter content vary with the different rubber tree ages.Soil organic matter content,total nitrogen content,total phosphorus content,total potassium content change with the rubber tree ages are showing a significant or very significant difference.The organic matter,total nitrogen and total phosphorus are generally consistent with the changing trend,all show decline first and then improve at different tree ages,especial decline most at the opening share of rubber tree.The total K with age do not have the significant rule.But in different regions and different nutrient levels,the degree of recovery and the characteristics are difference.This may be related to the soil parent material and the differences of rubber fertilizer management.The nutrient indexes including organic matter,total phosphorus,total nitrogen,total potassium of rubber plantation of the same age were decreased with the increase of soil depth.Soil nutrient of 0 to 20cm soil layer was higher than 20 to 40cm soil layer.This result was consistent with a lot of studies.The reasons are that the soil surface collected more litter,that rubber tree root(especially fine roots)was relatively shallow and mostly concentrated in the 0 to 20cm soil layer,that fertilization was applied to the soil surface.Different age rubber plantation soil nutrient indexes decreased and then increased with the growth of rubber trees.(2)The evolution of the physical of rubber plantation at different ages.From the overall situation of the rubber plantation in Hainan Province analysis,with the rubber tree growth,soil physical property indexes generally showed significant difference,but the trend of the index is not the same.Only in the field of rubber plantation maximum water holding capacity when the rubber tree growth trends in each region are consistent,showed a trend of decreased first and then increased.In different soil layers,the soil porosity,bulk density,and maximum water holding capacity of the soil in the same development stage of rubber plantation showed a certain change.(3)The relationship between soil nutrient components in rubber plantation.Multiple linear correlation analysis of soil organic matter,total nitrogen,total phosphorus and total potassium in rubber plantation was found that organic matter and total nitrogen,total phosphorus showed a significant linear correlation,and had a clear role to promote each other.This showed that organic matter has an important role in the management of soil nutrients in the rubber plantation,need to pay attention to the shortage of organic matter.There was no significant correlation between total potassium and other nutrients.But combined with the change trend of potassium,need to give the rubber tree some potash fertilizer during the growth phase and the opening phase.(4)Through horizontal comparative study,the results showed that rubber plantation soil nutrient was lower than that of secondary forest,to a certain extent in litchi orchard and Eucalyptus in recent years.The reasons were that stimulation tapping and rubber production increased took away more soil nutrients,that affected by the decline of economic benefits of natural rubber industry,large area rubber tree lacked of cultivation and management,less fertilization,random fertilization,no fertilization phenomenon existed generally,that Hainan rubber planting area was hilly region,not implement the technical measures of contour planting?protection forest?the young rubber plantation mulching resulted in a large number of water and soil and nutrients loss.(5)Study on the changes of soil physical and chemical properties of rubber plantation.The results showed that with the development of rubber plantation,soil properties decreased in young stage and increased in adult stage.This showed that the rubber plantation ecosystem had a certain ability to restore soil,if managed properly,had not only economic benefits,but also ecosystem service function.Natural rubber was a long-term economic crops,had a large scale cultivation in Hainan.In the rubber tree planting,must be contour cultivation and reasonable allocation of protective forest in accordance with technical regulations.In rubber plantation nutrient management and rubber tapping,must pay attention to reasonable fertilization,especially the rational use of organic fertilizer,and avoid strong cut and scarified. |
PDF Full Text Request