• Authors:
    • Narh, S.
    • Akponikpe, P. B. I.
    • MacCarthy, D. S.
    • Tegbe, R.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 102
  • Issue: 1
  • Year: 2015
  • Summary: This study set out to (1) calibrate and evaluate the performance of APSIM in simulating maize response to N, P and residue management and (2) identify strategies to reduce instability in crop production, and increase the efficiency of mineral fertilizer use. The response of maize to inorganic nitrogen (N) and phosphorus (P) additions were determined in the coastal savannah agro-ecology in the main rainy and secondary rainy seasons, of 2008 and 2009. Field experiments were set-up in a randomized complete block design with different levels of N (0-120 kg N ha(-1)) and P (0-30 kg P2O5 ha(-1)) mineral fertilizer. The APSIM model adequately simulated agroecosystem dynamics, resulting in the following RMSE values: anthesis (1.2 days), maturity (2.0 days), maximum LAI (0.18 m(2)m(-2)) total-biomass (543 kg ha(-1)), grain yield (318 kg ha(-1)), N uptake (12.6 kg ha(-1)), P uptake (2.2 kg ha(-1)) and in-season soil water content (0.01 mm). A long-term simulation study (30 years) showed that probabilities of obtaining higher yields were higher in the main growing season than in the secondary growing season. The efficiency of mineral N fertilizer use was also higher in the main growing season. The use of 40 kg N ha(-1) mineral N fertilizer in both seasons was more efficient than using 80 kg N ha(-1). The variability in the efficiency of mineral fertilizer use was higher in the secondary growing (44-96 %) than in the main growing season (27-48 %). Retaining crop residues yielded higher stability in grain production and increased the minimum grain yield production significantly. Applying 40 kg N ha(-1) and 30 kg P2O5 ha(-1) mineral fertilizer with crop residue retention will reduce the uncertainty in maize production, particularly in the secondary growing seasons which are characterized by prolonged drought spells. This study suggests that resource-poor farmers will be better off prioritizing the main growing season for rainfed maize production and applying a moderate amount (40 kg N ha(-1)) of N fertilizer rather than the 90 kg N ha(-1) currently recommended for the coastal savannah of Ghana in the secondary growing season because of the higher instability in yields associated with N fertilizer use in this season.
  • Authors:
    • Naab,J. B.
    • Mahama,G. Y.
    • Koo,J.
    • Jones,J. W.
    • Boote,K. J.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 102
  • Issue: 1
  • Year: 2015
  • Summary: Sustainable management practices are needed to enhance soil organic carbon (SOC) in degraded soils in semi-arid West Africa. We studied the effects of three amounts of nitrogen (N) (0, 60 and 120 kg N ha(-1)) and three amounts of phosphorus (P) fertilizer (0, 26 and 39 kg P ha(-1)) application over four seasons on maize residue production, residue C, N, and P concentrations, and their impacts on SOC, total soil nitrogen (TSN), and total soil phosphorus (TSP) in the 0-20 cm soil layer. Combined application of N and P fertilizers substantially increased maize grain yield on average by 294 % and biomass produced and returned to the soil by about 60-70 % compared with no fertilization. Annual C, N, and P inputs from crop residue were significantly higher with combined application of N and P fertilizer. The increased amount of crop residue and consequent increased residue C, N and P returned to the soil significantly increased SOC, TSN and TSP in the 0-20 cm soil layer after four seasons. There was a significant correlation between the amount of crop residues returned to the soil over four seasons and SOC (r = 0.82; P = 0.007), TSN (r = 0.75; P = 0.020) and TSP (r = 0.69; P = 0.039). We concluded from these experiments that returning crop residues, application of inorganic fertilizer improves SOC, TSN and TSP concentrations and enhances crop productivity. The farmers who traditionally remove crop residues for fodder and fuel will require demonstration of the relative benefits of residues return to soil for sustainable crop productivity.
  • Authors:
    • Owusu, E. S.
    • Ozor, N.
    • Acheampong, E. N.
  • Source: CLIMATIC CHANGE
  • Volume: 126
  • Issue: 1-2
  • Year: 2014
  • Authors:
    • Awo, M.
    • Schraven, B.
    • Laube, W.
  • Source: CLIMATIC CHANGE
  • Volume: 111
  • Issue: 3-4
  • Year: 2012
  • Summary: Climate change and land degradation result in decreasing yields and crop failures in Northern Ghana and have caused further impoverishment of Ghana's poorest region. Farmers have diversified their livelihoods to adapt to uncertain environmental conditions in various ways. While traditionally a diversification of the production and migration were the prime means of adaptation, many farmers have started to intensify their production by adopting shallow groundwater irrigation for vegetable gardening for Ghana's urban markets. This has helped to cope with a changing environment, ameliorated poverty and reversed rural-urban migration, while the local hydrology curbed an over-exploitation of groundwater resources, commonly associated with an uncontrolled farmer-driven expansion of groundwater irrigation. This research confirms that farmer-driven small-scale irrigation can play an important role in the process of climate change adaptation. However, while farmers tried to integrate in the larger economy, they have become subject to market failures that in their essence are caused by unfair and unpredictable patterns of global trade. It is this double exposure to global environmental change and economic globalization that need to be taken into consideration when local adaptive capacities are discussed. Many convincing arguments call for the revision of some of the most unfair and devastating economic practices; however, the need to enhance adaptive capacity towards global climate change for poor parts of the population in the south should be added to the discussion.
  • Authors:
    • MacCarthy, D. S.
    • Fosu-Mensah, B. Y.
    • Vlek, P. L. G.
    • Safo, E. Y.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 94
  • Issue: 2-3
  • Year: 2012
  • Summary: Under low input subsistence farming systems, increased pressure on land use and decreased fallow periods have led to a decline in soil productivity. The soils in sub-humid region of Ghana are generally poor and require mineral fertilizer to increase crop productivity. This paper presents the use of Agricultural Production Systems sIMulator (APSIM) to simulate the long term influence of nitrogen (N) and phosphorus (P) on maize (Zea mays L.) yield in Sub-humid Ghana. The APSIM model was evaluated at two sites in Ejura, on a rainfed experiment carried out on maize in 2008 major and minor seasons, under various nitrogen and phosphorus rates. The model was able to reproduce the response of maize to water, N and P, and hence simulated maize grain yields with a coefficient of correlation (R-2) of 0.90 and 0.88 for Obatanpa and Dorke cultivars, respectively. A 21-year long term simulation, with different rates of N and P mineral fertilizer application, revealed that moderate application of N (60 kg N ha(-1)) and 30 kg P ha(-1) improves both the long term average and the minimum yearly guaranteed yield. Variability in grain yield increased with increasing application of N fertilizer in both seasons. Treatments with P fertilizer application shows a similar trend for the major season and reverse trend for the minor season, thereby suggesting an interactive effect with rainfall amounts and distribution. Application of 30 kg P ha(-1) significantly increased the response to N. The response to mineral fertilizer (N and P) applications varied between seasons, suggesting the need to have a range of fertilizer recommendations to be applied based on seasonal weather forecast.
  • Authors:
    • Donkoh, S. A.
    • Amikuzino, J.
  • Source: African Crop Science Journal
  • Volume: 20
  • Issue: Suppl. 2
  • Year: 2012
  • Summary: Climate variability, the short-term fluctuations in average weather conditions and agriculture affect each other. Climate variability affects the agroecological and growing conditions of crops and livestock, and is recently believed to be the greatest impediment to the realisation of the first Millennium Development Goal of reducing poverty and food insecurity in arid and semi-arid regions of developing countries. Conversely, agriculture is a major contributor to climate variability and change by emitting greenhouse gases and reducing the agroecology's potential for carbon sequestration. What however, is the empirical evidence of this inter-dependence of climate variability and agriculture in Sub-Sahara Africa? In this paper, we provide some insight into the long run relationship between inter-annual variations in temperature and rainfall, and annual yields of the most important staple food crops in Northern Ghana. Applying pooled panel data of rainfall, temperature and yields of the selected crops from 1976 to 2010 to cointegration and Granger causality models, there is cogent evidence of cointegration between seasonal, total rainfall and crop yields; and causality from rainfall to crop yields in the Sudano-Guinea Savannah and Guinea Savannah zones of Northern Ghana. This suggests that inter-annual yields of the crops have been influenced by the total amounts of rainfall in the planting season. Temperature variability over the study period is however stationary, and is suspected to have minimal effect, if any, on crop yields. Overall, the results confirm the appropriateness of our attempt in modelling long-term relationships between the climate and crop yield variables.
  • Authors:
    • Andrasko, K.
    • Bosquet, B.
  • Year: 2010
  • Authors:
    • Yang, H.
    • Walters, D. T.
    • Dobermann, A.
    • Cassman, K. G.
  • Source: Annual Review of Environment and Resources
  • Volume: 28
  • Issue: 1
  • Year: 2003
  • Summary: Agriculture is a resource-intensive enterprise. The manner in which food production systems utilize resources has a large influence on environmental quality. To evaluate prospects for conserving natural resources while meeting increased demand for cereals, we interpret recent trends and future trajectories in crop yields, land and nitrogen fertilizer use, carbon sequestration, and greenhouse gas emissions to identify key issues and challenges. Based on this assessment, we conclude that avoiding expansion of cultivation into natural ecosystems, increased nitrogen use efficiency, and improved soil quality are pivotal components of a sustainable agriculture that meets human needs and protects natural resources. To achieve this outcome will depend on raising the yield potential and closing existing yield gaps of the major cereal crops to avoid yield stagnation in some of the world's most productive systems. Recent trends suggest, however, that increasing crop yield potential is a formidable scientific challenge that has proven to be an elusive goal.