Preliminary Study On The Improvement Of Albic Soil By Using Biochar

Density of Albic soils is high, which leads drought and logging on surface of soils and loss of water and soil from topsoil, and could be classified into low-productive soil. High porosity and low bulk density of biochar provide multiple services including ameliorating soil condition, which helps improve soil productivity. To explore potential function of biochar on ameliorating Albic soils in northeast of China, a pot study was conducted. We applied different rates of biochar (O、10、30、50t-hm-2) into albic horizon, examined change of soil porosity and water holding capacity, and response of root growth of soybean and yield. Finally, an appropriate application rate was proposed. Results are as bellow:1.Biochar reduced bulk density, improved soil structure and allocation of porosity:At rate of1Ot·hm-2, bulk density of Albic soils arrived at1.00g·cm-3, which got to ideal standard of1.1～1.30g·cm-3. When application rate continued, bulk density was too low for root to settle. It was the same for specific gravity of Albic soils. At10and30t-hm’2, plasticity index arrived at24.37and28.64%, which was apt for cultivation.Meanwhile, application rate of10t·hn-22was the best with total porosity of62.27%, similar to ideal ones for plant growth (50%to60%). Meanwhile, aeration porosity.2. Permeability of water was increased because of improving soil structure and porosity of albic-layer by adding biochar.The results showed that a significant reduction of numbered porosity of albic-layer, big porosity were observed at increase of biochar, while it also increased numbered big pores of albic horizon, big porosity and total numbers of pores (p<0.05). Total porosity of albic horizon at50t·hm-2of biochar reaching up to maximum (27.58%),539.91%higher than control treatments. Biochar significantly decreased the preferred ratio of albic-layer while increased pores, girth. When biochar was50t-hm"2, the peferred ration of blbic-layer reached to minimum (0.80), pores girth reached to maximum(17.72). The results showed that a sinnificant increase of permeability of water in albic-layer were observed as50t-hm"2>30t·hm-2>10t·hm-2>CK. When biochar was50t·hm-2, the primary permeability rate, mean permeability, and stable permeability,100min total permeability and index of saturated permeability were17.8,12.08,13.12,12.76and12.76fold higher than CK. The process of water infiltration after applying biochar into the soil could be fairly simulated by using Kostiakov, but it was not appropriate for CK. The results indicated that soil pore space is different from original porosity to secondary porosity which was formed by adding biochar.3. Biochar have positive effect on water holding and released ability of albic-layer.Biochar increases mass soil water content of all soil suction levels in albic-layer, and all showed that50t·hm-2>30t·hm-2>10t·hm-2>CK. Simulation results showed that bio-char increase the A、B value of empiric formulas of power function and equivalent crater of all soil suction levels in albic-layer, respectively, which indicated water holding ability of albic-layer increased greatly as the adding of biochar. Meanwhile, Biochar increases specific water capacity of all soil suction levels in albic-layer, and all showed that50t-hm-2>30t-hm"2>10t·hm-2>CK, indicating that water released ability of albic-layer was greatly increased. The comprehensive analysis showed that biochar increase the capillary water, saturated water content, field holding water, permanent wilting coefficient at the same time. Soil available water capacity was raised to a fairly high level because of field holding water increase greater than permanent wilting coefficient, indicating that Biochar have positive effect soil physical and chemical properties of albic-layer.4. biochar promote the numbers of microorganism and activities of soil enzymeBacterium numbers as maximum when biochar were301hm-2and50t hm-2,6.2fold higher than CK. Aminated bacterium, nitrogen-fixing bacteria, actinomycetes and total bacterium were maximum when bioCaron was50t·hm-2,24.29,12.09,7.83,7.10fold higher than CK. While fungus was maximum at30t·hm-2of biochar,8.33-fold higher than CK. Biochar increased the amount of urease, catalase, protease and cellulose, while decreased the amount of sucrose. A significant correlation was observed among actinomycetes and activates of other enzymes. The amount of sucrose exhibited negative correlation with the numbers of microbial in albic-layer;in contrast, urease showed positive correlation with fungus and actinomycetes. Catalase was positive correlation with bacteria, fungus and actinomycetes, and amount of protein enzyme was postitive correlation with actinomycetes, cellulose enzyme was positive correlated with aminated microbial, bacteria, fungus and actinomycetes.5. Biochar has a significant influence on the nutrient status of Albic horizon and promote soybean nutrient absorptionBiochar increased total N of the albic horizon in branching and flowering stage, and total P, S of albic horizon in every stage, the results have showed50t hm-2>30t hm-2>10t hm-2CK. The content of available phosphorus, potassium in albic horizon were increased by biochar, but the available nitrogen were decreased. Biochar did not show any obvious regularity that the impacts of EC and pH, but it might indirectly promote the soybean absorption of N, P, K, Ca, S and other nutrients, the total absorption of them of individual plant showed50t hm-2>30t hm-2>10t hm-2> CK. The distribution proportion of N, P, K, Ca, S in soybean root system gradually increased with the amount of biochar increased.6. Biochar promoted the soybean root morphology and yield formation in different extentBiochar increased dry weight, root length, volume, diameter, surface area, tip number of soybean at each growth stage. The root dry weight, root length, volume in mature stage reached its maximum at30t hm-2, increased164.10%,51.50%,120.95%, respectively that compared with CK. Although root dry weight density, length density, volume density, surface area, tip number of the topsoil in mature stage reached the maximum when the amount of biochar was50t hm-2, the principal analysis showed that root growth was the best when the amount of biochar was30t hm-2. Biochar also increased soybean specific absorbing area (absorbing area per gram root weight) and specific active-absorbing area (active-absorbing area per gram root weight) and deoxidization intensity and other physiological traits, it also promoted plant height, seed number per plant, grain weight per plant, biological yield and showed30t·hm-2>10t·hm-2>50t·hm-2>CK, grain weight per plant increased by21.89%compared with CK when the amount biochar was30t hm-2. These results indicated that the optimum range of biochar was about30t hm-2to the current crop.7. Biochar can improve the quality rating of albic horizonMaking a further evaluation for albic horizon quality, the results showed that50t h m-2>30t hm"2> lOt hm-2> CK. The quality index of albic horizon (CK) is0.06, belo nging to the low level (Ⅵ); The amount of biochar was10t hm-2that its quality inde x was0.50, belongs to the level (Ⅲ), quality index was0.75when the biochar dosag e was30t hm-2that belongs to a higher level (Ⅱ), quality index was0.84when the b iochar dosage was50t hm-2that belongs to the highest level(Ⅰ). Determined the mini mum dataset of quality evaluation index of albic horizon are effective water content, a vailable P, available K, ammonifying bacteria, bacteria, fungi, actinomycetes, cellulase, stable nitrogen-fixing bacteria though sensitivity classification, evaluation of quality ind icators correlation analysis and principal component analysis of comprehensive quality indicators. The correlation was0.95of dataset and evaluating results,while it has a go od representativeness.In summary, improving the permeability, soil available water through the improvement of pore structure, improving nutrient supply capacity through rich soil microbial formations to promote crop root morphogenesis, and even promote crop yields improvement when biochar applied into the albic horizon. Therefore, the albic horizon mixed with biochar to improve albic high was feasibile. But it is also found that crop yield and soil quality level in the quarter have no correspondence after biochar applied into soil, its reason remains to be further discussed.