Effects of cocoa pod ash and urea on soil chemical properties and the performance of kale (Brassica oleracea L.) in derived savanna zone of Nigeria

Abstract

Potted experiments were carried out at the Teaching and Research Farm, Landmark University, Nigeria between January and March (1st crop) and April and June (2nd crop), 2015. The aim was to investigate the effects of sole and integrated application of cocoa pod ash (CP) and urea fertilizer (UF) on soil chemical composition and performance of kale (Brassica oleracea L.). There were 12 treatments comprising 3 levels of UF (0, 100, 200 kg/ha) and 4 levels of CP (0, 5, 10 and 15 t/ha). The treatments were arranged in a Completely Randomised Design, replicated three times. For the 1st and 2nd crops of kale, CP alone and integration with UF, increased soil chemical properties compared with the control where neither CPA nor UF was applied. Treatments with 5 t/ha cocoa pod ash + 100 kg/ha urea fertilizer (CP5U100) and 5 t/ha cocoa pod ash + 200 kg/ha urea fertilizer (CP5U200) consistently had the higher values of N, K Ca and Mg in the soil after both the 1st and 2nd kale crops and the mean values of both crops. Treatments with CP5U100 and CP5U200 had significantly higher and similar values of plant height, number of leaves and other yield parameters (root weight, stem weight, leaf weight, stem girth and stem length) of kale compared with other treatments. Compared with the control, CP5U100 and CP5U200 increased the leaf weight of kale by 243 and 268%, respectively. Therefore, integration of cocoa pod ash at 5 t/ha with 100 kg/ha urea fertilizer may be recommended in the production of kale in the derived savanna zone of Nigeria to cut down on the use of urea and its rising cost. More research is, however, needed involving field experimentation and additional soil types to make a firm recommendation.