Comparison of municipal and agriculture-based solid waste composts: short-term crop-yield response and soil properties in a tropical Ultisol

Abstract

Most farming communities are reluctant to use municipal solid waste compost (MSWC) although the use of agriculture-based waste compost (AWC) is already highly popularized. The objective of this study was to comparatively assess MSWC and AWC considering their effects on soil acidity, salinity, fertility, and short-term crop yield response in a tropical Ultisol in Sri Lanka. Seven MSWC samples (samples named as S1 – S7) and two AWC samples (samples named as S8, S9) were applied in the field at 10 and 20 Mg ha⁻¹ rates in two consecutive years with bush bean and maize in the first year, and only bush bean in the second year. The soil was initially acidic (pH: 5.3–5.7) and non-saline (Electrical conductivity, EC_1:5 < 0.05 dS m⁻¹). The pH significantly increased with the application of MSWC (6.4–7.6), but not with AWC (5.1–5.7). The application of MSWC increased the EC_1:5 more significantly compared with AWC. Yields of both crops were > 35% lower compared with the expected average yield in all the treatments in the first year of cultivation. The yields of bush bean cultivation in the second year showed increases, however, slightly lower than the expected average yield. Yields were higher when the soils were comparatively higher in phosphorous (P) and potassium (K). Application of AWC did not produce high yields compared with MSWC. Results revealed that MSWC was comparable or better than AWC considering the crop yield response. However, the use of MSWC can be considered better suited for soils with more acidic conditions. The application of AWC is suitable, while MSWC is not, for soils with already high pH and saline conditions or when the expected crop prefers acidic soil reaction. Further experiments are required on effects of continuous applications on soils and methodologies for lowering the salinity levels of MSWC.