Modelling maize growth, development and yield for site specific fertilizer recommendation under Guinea Savanna Agro-ecological conditions in Ghana
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Date
2011
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Abstract
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 Kpalisogou. 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).
Sensitivity analysis results showed that the DSSAT model is highly sensitive to changes in weather variables such as daily maximum and minimum temperatures as well as solar radiation. However, the model was found to be least sensitive to rainfall. Similarly, the model was found to be sensitive to soil and genetic parameters of the cultivar.
The DSSAT model was used to conduct economic and strategic analysis to ascertain the most economically and efficient fertilizer rate that should be applied to achieve maximum harvest maturity yield and maximum returns. The result showed that 120-90-60 kg/ha N-P2O5-K2O is the most strategically efficient. However, 120-60-0 kg/ha N-P2O5-K2O is the most economically efficient fertilizer rate in the Guinea savanna agroecological zone of Ghana with a minimum and maximum return of GH ₡-155 and GH ₡ 570 respectfully. However 120-90-60 kg/ha N-P2O5-K2O recorded and average return of GH₡ 509.
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A thesis submitted to the Department of Crop and Soil Sciences, Faculty of Agriculture, Kwame Nkrumah University of Science and Technology, Kumasi, in Partial fulfillment for the requirements for the Degree of Master of Science in Soil Science