Abstract

The extent to which cricket frass placement and rate regulate fertility restoration and crop response in tropical acidic sandy soil remains insufficiently resolved. This greenhouse bioassay tested whether incorporated or surface-applied cricket frass differentially improved soil fertility and Chinese kale biomass, and whether these responses were rate-dependent. Cricket frass was applied by incorporation or surface placement at 3.125, 6.25, and 12.5 Mg (tonnes) ha−1 and compared with an unamended control. The frass had pH of 6.95, EC 19.6 mS cm−1, 10.7 g N kg−1, 8446 mg P kg−1, and 12,425 mg K kg−1 and a C:N ratio of 16.8. At 12.5 Mg ha−1, incorporation produced the greatest shoot dry biomass (7.16 g plant−1), exceeding surface placement (4.78 g plant−1) and the control (1.70 g plant−1). High-rate incorporation increased NH4+–N, net ammonification, available P, and microbial activity, reduced exchangeable acidity, and promoted greater nutrient uptake. Pearson correlation analysis showed that shoot biomass was strongly associated with plant nutrient uptake, soil P, pH, CEC, NH4+–N, and net ammonification, and was negatively associated with soil Al and exchangeable acidity. Both placement methods improved fertility and yield relative to the control, but incorporation was superior at the high rate. Surface placement remains useful where soil disturbance must be minimized, although field validation with larger soil volumes and rainfall-driven processes is required.

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