Research On The Formation Of Agrarian Acidification In Lichuan County And Its Prevention

Soil is the natural presentation of life. There is a great quantity of bacteria, funqi, algae and protozoa in every gram of fertile farmland soil, besides ten and thousands of roots and other casts. Soil is an interesting place for creature.It is also the most complex ecosystems and the most luxuriant biologic resource pool in nature. The existence of a great deal of creature leads to hearty metabolism of substance and energy. Not only is soil the product of the activities of creature and the cradle of life, but it also the object of biological habitats and effects of life as well as the birth and evolution of a hoed on earth. There is evidence proving that the property of soil and crop growth and agricultural production are closely related.By the research of changes of soil, we can search the reasons and analyse the technical countermeasures in time to mitigate the negative impact on agricultural production due to soil changes and promote the smooth development of agricultural production.Lichuan town is located in the southwest of Hubei Province. The east is on Enshi. The south is on Xianfeng County. The southwest is to Qianjiang county and Pengshui County of Chongqing province. The city crosses108°21’E-109°18’E,29°42’N-30°39’N,92km wide from east to west,105km from north to south. The total land area of the city is4605.2km2, in which the farmland110699.58ha, accounting for12.96%of the total area, the tree farm10043.65ha, accounting for48.64%, and lawn19605.69ha, accounting35.36%.Soil acidification in Lichuan is an important manifestation of the change of soil. It causes deterioration of soil physical properties, changes of soil nutrient supply, and activation of heavy metals and toxic elements in the soil, causing changes of soil micro-environment and the microbial flora, and affecting the normal growth of crops. It has become a major obstacle to improve the farmland soil productivity. So it is necessary to study the countermeasures thoroughly. In this study, historical documents were consulted, the organic fertilizer resources in the region, the labor migrant situation, conventional fertilization level data were investigated and surveyed; the sample’s pH, organic matter, available N, P and K,the precipitation pH value parameters of the arable soil in representation region were tested; soil acidification treatment and material screening test were launched. And progress in the phasal sense was obtained.(1)The study of serious acidification in regional cultivated land.The mean value of pH is5.12in study of regional cultivated land,1.38units lower than the second national soil survey in1982, in strong acidic level, ranging from 2.85to7.63. Compared with the second national soil survey (amplitude comparison of4.2～8.7), the highest value, mean and minimum values declined in sync. The alkaline soil whose pH>7.5had nearly disappeared, and strong acidic arable land with pH<4.5reached to33.23%, nearly300000acres. And the paddy’s pH changes less than dry land. Degree of arable soil acidification in the development of different parent materials:quartz sandstone> argillaceous shale> purple rock> Quaternary clay> limestone> alluvial material; of acidification in different soil type:yellow> brown> purple soil> yellow brown soil> paddy soils> aquic soil> limesoil.(2) The causes of the arable land’s acidification were worked out initially.It was first found that Lichuan is one of the areas with acid rain in China. The winter precipitation monitoring result alone showed the frequency of acid rain (including snow) had reached54.54%. The higher frequency of acid rain accelerated soil acidification. The analysis also showed that:precipitation (including acid rain) contributed63.04%to arable land acidification, which was higher than that of tillage, fertilizing and other human factors. Under the influence of a larger annual precipitation (average annual rainfall,1300mm), base cations in the soil leaching, the potassium in the cultivated soil decreased25.5mg/kg,and decreased by18.7%during24years, compared with the second national soil survey.Stop of conventional measures in controlling soil acidification. Due to the discovery of the cultivated soil’s "sub-podzolizing" reaction in the second national soil survey, conventional arable land acidification governance measures—Liming was stopped more than thirty years. Long-term soil acidity is not neutralized, speeding up the arable soil acidification process. A large number of partial uses of chemical fertilizer, especially long-term partial use of nitrogen and phosphate fertilizers, causes soil nutrient imbalance. Base elements in the soil colloidal particles such as calcium, magnesium are very likely to be replaced by hydrogen-ion, resulting in rapid decline in pH value. At the same time, in condition of high-yielding crop varieties being popular, bases of calcium, magnesium, potassium and other elements in the soil are over-consumed by the way of to being brought out the soil with the crop harvest and conventional fertilization has not been an effective complement, leading to development of soil acidification.The amount of organic fertilizer application has been reduced, so organic matter declines consequently. The analysis indicates that more than1000kg chemical fertilizer has been put into every hectare yearly in the studied district of farmland since2003. with an increasing rate of7.43%each year, especially nitrogen getting an increasing rate of9.14%each year. The amount of manure dosage seriously decreased, and the fertilization area is only half of the cultivation area, the application rate652kg/mu, reducing the soil organic matter content. The soil organic matter reduced by3g/kg during last24years, and thus decreased the acid buffering capacity, resulting in the acceleration of soil acidification.(3) The materials for controlling soil acidification were filtered.Sodium carbonate, lime,plant ash, large grain silicon (silicon fertilizer), commercial organic fertilizer and pig manure water were applied to Vegetables (carrots, the sphere cabbage), food (rice, maize),and fruit (pears) to study their impact on crop yield and changes in soil pH.The results displayed that:liming is practicable to govern farmland acidification, and it can neutralize soil acidity, improve soil nutrient availability, improve soil structure and kill the insects and disinfect; silicon fertilizer has some effect on governance of arable land acidification, which can be extended; commercial organic fertilizer with characteristics of both commercial fertilizer and organic fertilizer, is a good substitute of farmyard manure; plant ash a limited resource, manure requiring a lot of labor, making a certain limitation to use them in practice; the use of sodium carbonate is difficult, easily leading to injury of crop seeds and seedlings, resulting in the production, while pig manure water’s effect is not obvious.(4)Measures of governing soil acidification were figured out.Comprehensive study suggested that:①Widely applying lime and other alkaline minerals, and promoting silicon and alkaline fertilizer and commercial organic fertilizer gradually instead of manure, are fast and portable measures to control and study cultivated land acidification of some area, improve crop yields and quality, and enhance the quality of arable land. It can be promoted in similar areas;②The general promotion of soil testing and fertilizing, full use of resources, and maintaining the balance of the soil base cations, adding farmyard manure, and enhancing soil organic matter, can enhance the buffering capacity of the soil acidity.③The implementation of straw mulching cultivation, the development of tea cymbidium, blueberries and other acid-resistant crops, and utilizing weeds and straw of tanabe and corner to smoke fire fecal, can be used as important measures of controlling farmland acidification.