Utilization of Wastes for Sustainable Agriculture in Thailand

Abstract

In Thailand, soil loss by sheet and rill erosion at the degree that needs management was estimated to be as high as 1 million rai (160,000 ha) per annum. The loss was severe in sandy-textured soil planted to destructive crops such as cassava and usually occurred on sloping lands. The soils that were low in organic matter content (less than 3.5%) accounted for 208.3 million rai (33.3 million ha) or 65% of the total land area. Annually, there were many crop residues and agroindust and cassava wastes produced were 25.45, 9.09, 3.16, 1.44, and 4.50 million tons respectively. Animal wastes such as cattle manure, swine waste and poultry manure amounted to 16.80, 3.61 and 3.81 million tons per annum respectively. There were many experiments conducted by using these wastes for sustaining soil fertility and improve organic matter contents of soils. Generally, rice straw compost (RSC), rice husk and animal manure were widely used for paddy rice. RSC applied at low rate (less than 2,000 kg rai-1 or 12,500 kg ha-1) increased rice yield but it did not significantly increase soil organic matter and CEC after application in 3 consecutive years. RSC at 2000kg rai-1 could replace chemical fertilizer the rate8-4-4 kg rai-1 of N-P2O5-K2O applied for 22 years. Azolla applied either as green manure or dry mass could be a good N source for rice. For deepwater rice, Sesbania rostrata was effective as green manure. Castor meal (CM) and activated sludge cake (AS) from brewery factories were good N sources for acid soils and low fertile sandy soils. As an upland crop, cassava was usually planted on low fertile soil. Depletion of soil fertility was clearly observed year by year in the long-term plots where cassava was continuously grown without fertilizer application. If no fertilizer was sued, cassava stalk should be incorporated into the soil to maintain soil fertility. RSC and animal manure could produce sugarcane yields that were comparable to those produced by chemical fertilizer in many cases. RSC, animal nanure, CM, AS, and effluent of biogas production from swine wastes were good N sources for corn whereas filter cake form sugar refinery factory appeared to be a promising P source for crops and was comparable to triple-superphosphate in the long run. Rice straw mulch, mungbean as green manure and rice bean relay cropping were among good N sources for corn as well.