Research
Cowpea Yield as Affected By Level and Time of Mineral Phosphorus Fertilizer Application in the Guinea Savanna Agro-Ecological Zone of Ghana
Phosphorus, although not required in large quantities, is very critical to cowpea production because of its multiple effects on nutrition; shoot development and its influence on nodulation. Phosphorus application stimulates plant root growth, early flowering, enhances fruiting, initiate nodule formation as well as increase in yield of cowpea. In spite of this immense importance of P in soils, its availability to cowpea growth and development is influenced by several factors, which include level and time of application. Knowledge in level of P and time of application to facilitate timely availability of the P fertilizer to improve cowpea yield is critical in order to avertthe continues reduction of cowpea yield by farmers. As a result a 3x4 factorial experiment arranged in split-plot design was conducted at the University for Development Studies experimental site, Nyankpala near Tamale in the northern region of Ghana campus to determine the appropriate P fertilizer levels and timing of application. Three levels of P fertilizer; 24, 48 and 60 kg ha-1 P was applied at 30, 15 days before plating. However, a third application was implemented at sowing.
Modeling Maize Production towards Site Specific Fertilizer Recommendation in Ghana
The use of crop growth simulation models such as those incorporated into Decision Support System for Agro technology Transfer (DSSAT) are useful tools for assessing the impacts of crop productivity under various management systems. The maize growth model of DSSAT is CERES-Maize. To use it to predict fertilizer recommendation for maize (Zea mays L.) under Guinea savanna agro ecological conditions, data on maize growth, yield and development as well as data on soil and weather were collected from field experiment conducted during the 2010 growing season at Kpalesawgu in Ghana. The model was calibrated using various crop growth and development data observed at the field experiment at Kpalesawgu. Maize variety obatanpa was used in the experiment. The cultivar coefficient was calibrated with data collected from the field experiment. All measured data on phenology, grain yield and biomass from the field experiment were used for model validation and simulations. Validation results showed good agreement between predicted and measured yields with a NRMSE value of 0.181. Highest observed mean harvest maturity yield of 3831and 3795 kg/ha were obtained from plots which received 120-90-60 and 120-60-60 kg/ha N-P2O5-K2O respectively. However, the model under predicted weight per unit grain. The mean difference between observed and simulated by-product produced at maturity and top weight at maturity was significant (P ≤ 0.001).In general, maize yield simulation by DSSAT under Guinea savanna agro-ecological conditions was good. Average predicted harvest maturity yields were very close to measured values with MD of 336.0, RMSE of 498.77, NRSME of 0.181 and simulated and observed mean yields of 3096 and 2750 kg/ha for the entire treatments respectively. The mean difference between predicted and observed was not significant. The highest harvest maturity yield predicted and observed was achieved with 120-90-60 kg/ha N-P2O5-K2O. The predicted and observed average mean yield were 383
