The Impacts Of Biochar On The Physical And Chemical Properties Of Limestone Soil And Crop Growth

Carbonate rock is chemical sedimentary formed in cleaning oceans, and its acid insoluble content is low, therefore, the amount of limestone soil by weathering is small, and the soil is thin and more viscous component. Biochar is a multi-carbon product formed in organic straw smoldering at low temperatures, which has rich pore, low specific gravity, and a good improvement effect on limestone soil, including the improvement of the physical structure of the soil, soil moisture, nutrient status and gas migration and so on. Through the out-door pot experiment, this paper explores the improvement effect of biochar on limestone soil widely distributed in karst area and crop yield-increasing mechanism.Potted Time:from April26,2013to August12,2013Potted device:diameter31cm, height50cmPotted treatment:(1)The improvement of brown limestone loam and red limestone loam by the different dosage of bagasse biochar (B1).(2)The improvement of brown limestone loam by bagasse biochar (B1) and bamboo biochar (B2).Test method:field monitoring, periodic sampling and laboratory analysis methodsAnalysis Indicators:In the process of crop growth, crop height, chlorophyll content, soluble sugar content, soluble protein content, net photosynthetic rate, biomass and yield are measured. After harvest, the soil’s mass water content, unit weight, ph value, organic carbon content, nutrient content and content of available nutrient element are measured.The main results are:1. The Impact of different dosage of bagasse biochar on brown limestone loam and red limestone loam. The unit weight of two limestone loam becomes lower (P＜0.05) with increase of B1. But the ph value is different, the ph value of red limestone loam increase while the ph value of brown limestone loam decrease. Two limestone loam’mass water content, organic matter, total nitrogen, total potassium, phosphorus and potassium levels increase with increase of B, while the nitrogen content decreases with increase of B1. The change of total phosphorus content is closely related to soil type and crops. The red limestone loam’organic matter, total nitrogen, and effective phosphorus content increase higher than the brown limestone loam, while the unit weight reduction and total potassium and available potassium content increase of red limestone loam is lower than brown limestone loam.2. The improvement of brown limestone loam by bagasse biochar and bamboo biochar. The unit weight of brown limestone loam decreased with the increase of B1and B2(P＜0.05). The impact of different types of biochar on mass water content and ph value of brown limestone loam is widely different. When B1applied, mass water content of brown limestone loam (P＜0.05) increase, but the increases of ph value is small even decrease; when B2applied, mass water content of brown limestone loam did not change significantly, but pH value was significantly (P<0.05) increased. Brown limestone loam organic matter, total nitrogen, total potassium, available phosphorus and available potassium content increase with the increase of biological carbon dosage, while available nitrogen decrease with the increase of biological carbon dosage, and total phosphorus content relate to the cultivation crop. The increasing impact of B1on brown limestone loam organic matter, total nitrogen, total potassium, available phosphorus and available potassium and the decreasing impact of unit weight are greater than B2, while the decreasing impact of nitrogen content is less than B2.3. The extent of biochar impact on soil properties is closely related to the crop species. In this research, the increasing impact of the ph value, total nitrogen, organic matter, phosphorus, and potassium content of the limestone loam planted soybeans and the decreasing impact of the unit weight are greater than the limestone loam planted corn. The total phosphorus content of brown limestone loam planted soybeans decrease, while the total phosphorus content of brown limestone loam planted corn increase.4. Applying bagasse to brown limestone loam and red limestone loam have influence on crop growth. With the increase of B1, soybean plant height increase in soybeans each growting season. The corn height is suppressed in seedling stage, and has an increasing trend with the increase of B1in jointing stage. Maturity, soybean biomass dosage increases with the increase of B1, while the change of corn biomass dosage is different. In addition, biochar play a role in promoting the accumulation of grain, making the production of soybeans and corn are added with the increase of the amount of B1increases. The use of B1in red limestone loam has a greater promoting influence than in brown limestone loam.5. Bagasse biochar and bamboo biochar have an impact on crop growth. Soybean height increase at first and then decrease in each growing season. The corn height is suppressed in seedling stage, and disappeare with corn growth. The height increases with increasing biochar. Maturity, the biomass of soybeans and corn increases at first and then decrease. In addition, lower concentrations of B1and B2promote the accumulation of substances grain crops, and corn and soybean production increase. But if B1and B2application rate is too high, it is not conducive to the accumulation of dry grain crop, leading to lower yields of corn and soybeans. The promoting effect of B1on crop growth is larger than B2.6Adding biochar to limestone loam has definite influence on the crop physiological characteristics. The net photosynthetic rate of soybean and corn have different improve in varying degree. In nutritional physiology of crop leaves, crop chlorophyll, total soluble sugar, and soluble protein content were improved. Soybean chlorophyll, total soluble sugar, and soluble protein content decrease with the crop growth; corn chlorophyll content decreases with the growth and development of crop, and total soluble sugar and soluble protein content are maximum in the jointing stage, while they are minimum in the heading date.