Soil nutrient status and enzyme activity in post harvest soils treated with urban and agricultural waste composts

A field experiment was conducted to evaluate the maximum loading rates of urban and agricultural waste composts on soil nutrient status and enzyme activity in vegetable-vegetable (tomato-bhendi) and cereal-pulse (maize-soybean) crop sequence for two years at College of Agriculture, Acharya N G Ranga Agricultural University, Hyderabad. During first season crops, the treatment with 40 tonnes USW compost ha(-1) showed maximum OC, i.e. 0.92 and 0.90% in maize and tomato fields, whereas in second year it was 0.92 and 0.93% in bhendi and soybean fields respectively. The nutrient reserves (N, P, K, Ca, Mg, S, Fe, Cu, Mn and Zn) were more in composts treated plots over RDF and control. The available N content ranged from 196 kg ha(-1)(control) to 275 kg ha(-1) (40 tonnes USW compost per ha (TC16) in tomato, 205 kg ha(-1) (control) to 282 kg ha(-1) (T16) in maize, 183 kg ha(-1) (control) to 278 kg ha(-1) (T16) in bhendi, 191 kg ha(-1) (control) to 284 kg ha(-1) (T16) in soybean post harvest soils respectively. Availability of all the cationic micronutrients, i.e. Zn, Fe, Cu and Mn were also significantly influenced by the application of composts. USW compost with 40 t ha(-1) exhibited more micronutrient build up. The higher availability at higher levels of composts was ascribed to mineralization of the compost, reduction in fixation by organic matter had complexing properties of these composts with micronutrients. The treatment with 40 t USW compost ha(-1) registered highest urease (20.1, 21.4, 20.9, 22.0 microg g(-1) soil), phosphatase (37.1, 40.9, 38.7, 41.0 microg g(-1) soil) and dehydrogenase (26.0, 28.6, 26.4, 29.0 microg g(-1) soil) activity in post harvest soils of tomato, maize, bhendi and soybean respectively, over other treatments and the lowest activity was observed in control plot.