There has been massive information on the success of biochar application in increasing agricultural productivity marginal soil. It is generally believed that biochar improves soil physical, chemical, and biological properties, consequently, increase crop yield. There was almost no information on the use of biochar for fertile soils. On the other hand, Magelang Regency the agricultural lands lay in the area of the volcano. These areas are the main supplier of agricultural products for Central Jawa and other places. Therefore, a strategy is needed to maintain the sustainability of agricultural land productivity. The aim of the present experiment was to introduce the use of biochar to maintaining the fertility of the soil in this area. Our first experiment dealing with the use of bamboo biochar in reducing the use of phosphorus (P) fertilizer in fertile soil. The experiment was carried out in the Bandongan District of Magelang Regency. An area which is surrounded volcanoes. The experiment involved a series of P applied, namely, 0, 25, 50, 100, 200 and 400 kg of SP3 ha-1. They were applied with and without biochar. Mung bean (Vigna radiata) was used as an indicator plant. The results showed that the presence of biochar (1) reduces the use of P fertilizer up zero, (2) decrease in the need of P fertilizer from 50 kg SP36 ha-1 to obtain the optimum yield of Mung bean. and (3) the optimum yield of Mung bean was consistently higher in bamboo biochar treated soil than without biochar. The decrease of Mung bean yields due to application bamboo biochar without P applied. Moreover, the reduction P application in bamboo biochar treated soil than without biochar to obtain optimum yield, indicating, that bamboo biochar may be able to dissolve insoluble P residue from the previously applied P. It may be presumbaly that the increase of P availability of P to plants due to the rise soil pH caused the increases in soil soluble P and activity of P solubilizing bacteria.
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