Dolomite-based Calcium-magnesium-silicon Soil Conditioner And Its Effects Of Soil Acid Treatment And Improvement

The problem of soil acidification is more prominent in southern China especially red soil regions.Agricultural intensification and high multiple cropping index and extensive use of chemical fertilizers intensified the acidification.Soil acidification will delined soil fertility and damaged the soil micro-ecology,which will seriously affect crop growth,cause decrese of crop quality and yield,and restrict the sustainable development of agriculture in the region.Therefore,soil acids treatment and improvement must be carried out to maintain and promote agricultural development in southern China.The currently used method of soil acidification treatment is to apply lime and other alkaline industrial and agricultural products.However,long-term application of lime will cause the soil craking and compaction and have the risk of burning users.For those reasons,it is particularly important to develop soil conditioner that is as effective as or better than lime in treating soil acid and can avoids the harms caused by lime application.In this paper,natural mineral dolomite is selected as the raw material,and calcined and non-calcined calciummagnesium-silicon soil conditioner or amendments are developed through different processing.Through incubation experiments,the soil conditioners’ properties and potential ability to treat soil acids were clarified.Through field experiment,effect of calciummagnesium-silicon conditioners on treatment and improvement sisal garden soil acids was studied.Research results would provide theoretical and technical support to develop natural dolomite calcium-magnesium-silicon soil conditioner and to treat soil acids by use of the conditioner.The main results were as follows:1.Following two techniques to manufacture calcium magnesium silicon soil conditioner from dolomite were determined.1)The first one is no calcining process being foumulation of calcium,magnesium and silicon raw material,mechanical grinding(particle size < 0.15mm)and mixture.2)The soncond process is low temperature calcining technique.The main parameters are formulation and raw material,grinding the dolomite rack into particle with 3 mm in diameter,calcining under 850℃ for 1 to 2 hours.Both un-calcinated and calcinated calcium magnesium silicons can be applied directly.The latter has a better effect of reducing active acid than the former,while the former has a better effect of reducing latent acid than the latter.Low temperature calcination for 1 h can significantly enhance the activity and alkalinity of dolomite and increase the effect of reducing active acid of calcium magnesium silicon.2.While neutralizing soil acid,the calcium magnesium silicon soil conditioner can release and supply calcium and magnesium nutrients to plants.The calcium and magnesium release curve devided into three phases being rapid release,uniform release and slow release.Among them,the release rate of calcium is greater than that of magnesium.Richards equation is the most suitable one to fit the release characteristics of calcium and magnesium from calcined dolomite and predicte the release rate of calcium and magnesium.3.It is proved by soil incubation that the calcined calcium magnesium silicon conditioner is better than lime to treat and improve soil acides.During the 35-day cultivation period,the soil pH can be increased from pH 4.51 to around pH 8 and the soil pH can be maintained constantly.The uncalcined calcium-magnesium-silicon conditioner is able slowly to increase the pH of the soil during the 35-day incubation which is the same effective of lime treatment.However,the soil pH value is 2.44 units higher than that of CK on average.4.Under field experiment condition,one year after application of uncalcined calcium magnesium silicon soil conditioner combined with conventional fertilizer,the soil pH value increased by 0.25 units.The soil pH increased by 0.57 units compared with that of the soil treated with conventional fertilizer.Total exchangeable acid content of the soil decreased by56.01% and tatal exchangeable aluminum decreased by 60.19%.Cation exchangeable capacity increase significantly because the increase of exchangeable calcium and magnesium ion content.The exchangeable calcium and magnesium ion content increased by1.44 times and 3.04 times respectively.5.At sisal harvested stage,one year after the application of uncalcined calcium magnesium silicon soil conditioner combined with conventional fertilizer,the total number of new leaves increased by 2.56% and the yield increased by 5.58% compared with those of control treatment.