Current Acidification Status Of Farmland In Enshi Autonomous Prefecture And Primary Exploration On Deacidification Effect Of Soil Conditioner (Lime,ect.)

Since the 80 s of last century,90% farmland in China has shown different degrees of acidification.Over the past 25 years,the p H value of almost all soil types in China has decreased by 0.13 to 0.80,a decreasement of 0.5 in average,soil acidification is very common.Enshi is located in the hinterland of Wuling Mountainous area in Hubei province,which soil acidification is increasing under the influence of environment,climate and other natural factors,crop cultivation,fertilization habits and other human factors.Due to soil acidification induced agricultural production and quality of the problem is gradually emerging and expanded,become the new potential dangers of steady development in agricultural production in Enshi Autonomous Prefecture.In order to comprehensively understand the soil acidification status of cultivated land in Enshi Autonomous Prefecture and similar areas,to provide the basis for the formulation of soil acidification control and control measures,soil p H during the past three decades was analyzed,datasets are from the Second National Soil Survey（1980-1983）and the Cultivated Land Quality Evaluation（2010-2013）.The combination of culture experiment and pot experiment was used to study the effect of different soil conditioners on soil p H and crop growth,using the field experiment to further verify the effect of applicated lime and to determine the appropriate application rate of lime.The main results were as follows:1.At Enshi Autonomous Prefecture,farmland soil showed an obvious acidification trend during the past three decades,with spatial variation of higher in the eastern part and lower in the western part of the region.Furthermore,soil p H decline occurred among different land use types in different areas.During the Second National Soil Survey,the p H of cultivated land is 6.5,after 30 years the soil p H of cultivated land decreased to 5.6,which declined 0.90 units on average,upland soil acidification was severe than paddy soil.2.The direct cause of soil pH decline in Enshi Autonomous Prefecture is the strong effect of human factors.It is mainly because of unreasonable fertilizer combination,fertilizer ratio change,more base cations taking away by high crop yield and long-term lime disused.3.The effects of acid reduction on different types of conditioner has different,which works best was lime,it’s compared with the control treatment increased 0.66 p H unit,the content of exchangeable Al3+ were decreased 2.01 cmol/kg,respectively,until 90 day.Though the treatment of rape straw had not reduced the soil acidity effectively,but still can obviously promote the crop growth,which can be used as acidic soil improvement material.So in actual production,should adjust measures to local conditions to application of various regulating substances to promote crop growth.4.The optimum evaluation index for the evaluation of alkaline materials to improve acid soil is the potential acid（exchangeable acidity,exchangeable Al3+ and H+）.The effect of low lime（≤ 0.9 g/kg）on the improvement of soil p H was not significant,but its effect on reducing the potential acidity of soil was significant,and the results of barley seedling test showed that lime can significantly increase the biomass of barley seedlings.This suggests that soil p H,as a reflection of soil acidity,has a simple and rapid test,but it is the one-sided to use only p H to assess acid soil improvement.5.It had verified that Ca（OH）₂ titration is a feasible method to calculate lime requirement.Under the condition of this study（p H3.9）,the application of lime improved soil significantly promoted the growth of barley seedlings,and the amount of lime was closely related to the soil improvement effect.The amount of lime was 1.8 g/kg of soil（equivalent to 4 t/hm² lime）improved the acidity of soil,which was consistent with the requirement of 1.76 g/kg calculated by Ca（OH）₂titration.6.Field test results were consistent with the culture test.Application of lime can increase corn yield significantly,under the soil conditions of p H 4.31（Hefeng County）and p H 5.03（Lichuan City）,taking the corn production as the standard,the appropriate amount of lime were 3000 kg/hm² and 2250 kg/hm²,the increasing ratio were 57.1% and 9.1%,respectively.Under the field conditions of p H 5.03,after a season of the first crop planting could increase the soil p H by0.68 units under the lime dosage of 2250 kg/hm².