Combined effect of biochar and castor cake on soil properties and yield of Amaranthus caudatus

Abstract

ABSTRACT

This study investigated the effects of combined applications of biochar and castor cake on soil chemical properties, growth, and yield of Amaranthus caudatus. Screenhouse and field experiments were conducted at Kwara State University, Malete, and the National Centre for Agricultural Mechanization (NCAM), Idofian, Kwara State. Screenhouse experiment was arranged in a Completely Randomized Design, while the field trial followed a Randomized Complete Block Design with three replicates. Treatments included different ratios of castor cake and biochar applied at 10 t/ha (30+70%, 40+60%, 50+50%, 60+40%, and 70+30%), NPK fertilizer at 100 kg N/ha, and a control. Results from the screenhouse study showed that combined applications of biochar and castor cake significantly enhanced growth and dry matter yield of amaranths. In the field experiment, the treatment comprising 60% castor cake + 40% biochar increased yield by 79.5% over NPK and 88.8% over the control after the first cropping. Its residual yield (12,094.3 kg/ha) was also significantly (p < 0.05) higher than that of NPK. The 70% castor cake + 30% biochar treatment significantly improved soil organic carbon, nitrogen, phosphorus, and potassium. Overall, application of 60% castor cake + 40% biochar at 10 t/ha is recommended for improving soil fertility and amaranth production.