Abstract:
Composting of wastes has become popular worldwide because it provides an organic fertilizer, when considering the continuous flow of municipal waste. Although municipal solid waste compost (MSWC) is commonly used for agriculture in many countries, Sri Lankan farmers are still reluctant to use it. On the other hand, the use of agriculture-based waste compost (AWC) is highly popularized. The objective of this study was to compare MSWC and AWC considering their effects on short-term crop yield response in an Ultisol. Seven MSWC samples (S1–S7) and two AWC samples (S8, S9) were used in the field at rates of 10 and 20 Mg ha–1, with chemical treatment (inorganic fertilizer recommendation/Department of Agriculture) and a control (no amendment). Bush bean (Phaseolus vulgaris) was used as the crop. The average expected yield (YEX) of bush bean in Sri Lanka is reported to be 6000–10000 kg ha–1. At the low application rate (10 Mg ha–1) in most treatments including the chemical (except in S5, S7, S8), the yield of bush bean showed >50% of the YEX. Six of these treatments did not show any significant differences in yield (p< 0.05), where the highest yield was about 65% of the lower level of YEX (6000 kg ha–1). Considering the yields at both 10 and 20 Mg ha–1 rates, the highest yield obtained was about 60–65% of the lower level of YEX. Results revealed that the yield of bush bean with compost treatments were well below the lower level of YEX, in almost all the treatments. The P requirement of bush bean is not met as the available P levels in composts were originally low. The original available soil P levels were also low (1.84 mg kg–1). Therefore, low P levels in compost might be the reason for the very low yield levels in all the treatments. However, when compared to recommended chemical fertilization, the compost application did not lower the yield, which might be a result of high leaching of nutrients due to sandy nature of soils. The 10 Mg ha–1 rate seemed sufficient to obtain substantial yield for bush bean at home garden levels under tested soil conditions. No significantly higher yields (p< 0.05) were observed with AWC compared with MSWC. Basic analysis of composts showed that the nutritive characteristics (N, P, K) of MSWC were not lower when compared with that of AWC. The study revealed that MSWC has performances comparable to, or better than, AWC, in contrast to the widely acknowledged opinion of Sri Lankan farmers on higher nutritive value and better crop productivity of AWC.
