EFFECTS OF FERTILIZER TYPE AND HARVESTING TIME ON YIELD OF CASSAVA (ManihotesculentaCrantz) IN IBADAN, NIGERIA

Abstract

Cassava productivity is limited by soil fertility status and maturity period. Frequently used mineral fertilizer is expensive and detrimental to soil health and productivity while information on specific harvest period is scarce. Thus, studies were conducted to assess the influence of Organomineral Fertilizer (OF) and harvesting period on cassava yield. Field experiments were conducted at Ajibode and Oluana in Ibadan. Five OF rates (1.5, 2.5, 3.5, 4.5, 6.0 t/ha), NPK 15:15:15 at 600 kg/ha and No Fertilizer (NF) treatments were evaluated on the performance of two cassava varieties: TMS 30572 (V1) and TMS 92/0326 (V2). Cassava (main plot) was planted at 10,000 plants per hectare and fertilizer (sub-plot) applied at planting using a split-plot arrangement in a randomized complete block design with three replicates. After harvest at 12 Months After Planting (MAP), cassava was replanted in-situwithout fertilizer application to assess the residual effects of fertilizer. Optimum fertilizer rate was selected based on cassava performance and subsequently used to assess the best period of harvest at 9, 12, 15 and 18 MAP. Data on Plant Height (PH) and Number of Leaves (NL) at 1-6 MAP, Shoot Yield (SY), Root Yield (RY), Harvest Index (HI) and Root Dry Matter Yield (RDMY) were analysed using ANOVA at p= 0.05.

The mean NL (118 ± 0.37) at 6 MAP obtained with 3.5 t OF/ha was significantly higher than that of NF (82) treatment. Similar result was obtained for SY and PH while RY (36.5, 31.8 ± 0.49 t/ha) recorded in 2.5 and 3.5 t OF/ha treatments respectively were significantly higher than NF (21.5 t/ha). The same results were obtained for RDMY and HI. The RDMY of V2 (12.3 ± 0.67 t/ha) was significantly higher than forV1 (10.5 ± 0.41 t/ha). Highest RDMY (13.2 t/ha) obtained with 2.5 t OF/ha was comparable with yields of higher rates of OF and NPK. Residual effects of OF rates above 1.5 t/ha produced significantly higher RY of 36.8 t/ha (4.5 t/ha) > 36.7 t/ha (6.0 t/ha) >35.9 t/ha (3.5 t/ha) >31.6 t/ha (2.5 t/ha) than NPK (19.8 t/ha) and NF (18.9 t/ha) in the first season. Similar trend was observed in the following season on RDMY and HI. The RDMY of 17.6 t/ha and 17.2 t/ha obtained at 15 MAP (V2 and V1 respectively) were significantly higher than that obtained at 9 MAP (6.6, 10.9 t/ha) and 12 MAP (7.1, 11.8 t/ha) in V1 and V2 respectively. The RDMY of V1 (18.8 t/ha) and V2 (13.2 t/ha) at 18 MAP were comparable with that obtained at 15 MAP. Application of OF at 2.5 t/ha and NPK produced RDMY of 15.0 t/ha and 14.2 t/ha respectively which were significantly higher than that of NF (7.8 ± 0.54 t/ha).

Optimum root yield of cassava was obtained with application of 2.5 t/ha of organomineral fertilizer. One application supported optimum crop yields in two cropping seasons. The best time to harvest TMS 30572 and 92/0326 in Ibadan was at 15 months after planting.