Compost and Nitrogen Fertilizer on Maize (Zea Mays L) Growth and Yield and Residual Effects on Cowpea (Vigna Unguiculata (L) Walp) In a Rotation

Abstract

A field experiment was conducted at the University of Ghana research farm to evaluate the influence of compost and Nitrogen fertilizer on soil improvement, growth and yield of maize (Zea mays L) and residual effects on cowpea (Vigna unguiculata (L) Walp) in a rotation. The study area is within the coastal savannah ecological zone of Ghana. Two separate experiments were conducted from July to November, 2016 and from December, 2016 to February, 2017. The experimental set up used was a 2×4 factorial randomized complete block design (RCBD) with 3 replications. The factors were 2 levels of compost (0 and 4t/ha) and 4 levels of N fertilizer (0, 40 kgha-1, 80 kgha-1 and 120 kgha-1). For the first experiment data was collected on soil chemical and physical properties, plant growth, yield and yield components of maize. For the second experiment, data was collected on soil physical and chemical properties before planting, plant growth, yield and yield components of cowpea. The results showed that the application of compost at 4t/ha together with different N fertilizer levels (120 kgNha-1 and 80 kgNha-1) significantly (p<0.05) increased growth and yield parameters of maize. Compost applied at 4t/ha in combination with 120 kgNha-1, 80 kgNha-1 and 40 kgNha-1 significantly (<0.05) increased maize plant height at 6 WAP (by 1.8%) and 8 WAP (by 1.9%), grain yield (9.5%), Stover yield (9.4%), N uptake (9.3%) and P uptake (26.1%) than when the inorganic fertilizer was used alone at the same rates. The interaction effects between compost at 4t/ha and N fertilizer at 120 kg/ha, 80 kg/ha and 40 kg/ha also significantly influenced maize at silking. For that of the residual effects of compost in combination with N fertilizer on cowpea in the rotation, a similar trend was recorded. Residual effects of compost and N fertilizer significantly (<0.05) increased growth and yield parameters of cowpea. Compost at 4t/ha combined with 40 kgNha-1, 80 kgNha-1 and 120 kgNha-1, increased seed yield by 12.0%, 10.0 % and 18.2 % respectively higher than results iii obtained without compost. It was therefore concluded that the compost at 4t/ha in combination with N fertilizer at 80 kgNha-1 level could be used as an alternative or supplementary source of nitrogen fertilizer to enhance maize productivity in the coastal savanna zone and enrich the soil for the follow up crop.