Effect of Rice Hull Biochar on the Fertility and Nutrient Holding Capacity of Sandy Soils
12 Pages Posted: 11 Feb 2016
Date Written: December 30, 2015
In the Philippines, under an integrated and diversified system of farming called Palayamanan, rice hull biochar (carbonized rice hull) has a lot of uses. Among other things, it is popularly used as soil conditioner and as main ingredient in the production of organic fertilizers. It is also used as bedding or absorbent material to facilitate urine and manure collection as well as help eliminate foul odor in poultry, swine and livestock. Once saturated, it is collected and applied to the soil as fertilizer. This study tries to further explore more uses of biochar and was generally conducted to determine the effects of rice hull biochar on the growth of upland kangkong and peanut and its effects on residual properties of sandy loam soil. Specifically, it aimed to (a) determine the appropriate level of rice hull biochar for peanut and upland kangkong grown in sandy soils, (b) evaluate N, P and K uptake of peanut and upland kangkong with different rates of rice hull biochar grown in sandy soils, and (c) evaluate the nutrient holding capacity of rice husk biochar in sandy soil. The experiment was carried out in a sandy loam with the following particle size distribution: 71.22% sand, 20.41% silt, and 8.37% clay; had a pHKCl of 4.93 , 0.64 % organic C, 0.16% total N, 1.53 mg kg-1 extractable P, 2.88 cmol kg-1 soil exchangeable Al, 3.08 cmol kg-1 soil exchangeable acidity, 0.25 cmol kg-1 soil exchangeable K, 3.57 cmol kg-1 soil exchangeable Ca, 1.38 cmol kg-1 soil exchangeable Mg, and 0.25 cmol kg-1 soil exchangeable Na. There were six treatment combinations from levels of amendment (0, 10, 20, 30, 40 and 50 g kg 1 soil). The processed biochar was applied at levels specified in the treatment on oven-dried weight basis. It was added and mixed well with the soil just immediately before filling the pots. The pots were allowed to stabilize for 3 days before planting. Blanket application of 70 mg each of N, P2O5 and K2O kg-1 soil using urea, solophos and muriate of potash was done five days after seedling emergence. Urea and muriate of potash were applied as aqueous solution while solophos was applied as granules. A linear trend in the liming benefit and positive change in pHKCl with biochar application were observed in two “plant biotest” especially at higher levels (30, 40 and 50 g kg-1 soil). On the other hand, the positive change in extractable P due to residual effect of rice hull biochar application was obtained even at 10 and 20 g kg-1 soil in both upland kangkong and peanut. In peanuts, direct effects of application of uncharred or charred poultry litter resulted in better plant growth, nodulation, biomass, and K uptake than the control plants. From the results of the study, it can be concluded that the application of biochar can enhance fertility of acid sandy loam soil. The rice hull biochar holds nutrient in place that is needed for plant growth and development. Application at 30-40 g kg-1 soil appears to be the most appropriate rate for both upland kangkong and peanut grown in acid sandy loam soils.
Keywords: biochar, nutrient-holding capacity, organic fertilizer, rice hull, sandy soil
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