Performance evaluation of reservoir-based irrigation schemes in the Upper East region of Ghana

The design of relevant adaptation strategies for water users in irrigation schemes in drylands of Sub-Saharan Africa requires up-to-date information about the current performance of these schemes in view of rapid changes in climate and land use, population growth, and competing water demands. The entire system of two (a small- and a medium-scale) irrigation schemes shared by multiple users in the Upper East region of Ghana were examined, including the water reservoir, water conveyance and distribution network, cropping fields, and management entity. First, multi-level performance indicators with relevance to water delivery, water utilization, and agricultural production were adapted and applied based on measurements of meteorological, soil and groundwater parameters, irrigation water inputs, crop management and yields for two rainy and dry seasons during 2014–2016 in prevalent cropping systems. For field-level evaluation, the FAO AquaCrop model was applied to develop an improved year-round irrigation schedule for dry-season cultivation of tomato and to assess a possibility for supplemental irrigation of maize in the rainy season under “wet” and “dry” climate scenarios. Finally, a scenario-based analysis of irrigation performance was conducted at scheme scale for the period of 2015–2030 using the Water Evaluation and Planning System (WEAP), a decision support modeling tool. These modeling scenarios considered the observed rainfall variability, introduction of supplemental irrigation in the rainy season, irrigable area expansion, and system efficiency improvement. Technical factors, such as underutilized reservoir storage capacity and deteriorated conditions of water delivery infrastructure strongly undermined the irrigation system performance. In particular, the medium-scale irrigation scheme utilized less than 40% of total storage, whereas the small-scale scheme utilized about 70% of the storage. The examination of field-level water management practices suggests that an application efficiency of 58–68% is achievable in both schemes by improving the irrigation scheduling of the major crops. Overall system efficiency can be increased from 50% to 68% by reducing water conveyance network losses and by eliminating over-irrigation of fields. The AquaCrop simulations show that improved irrigation schedule for dry-season tomato cultivation would result in a water saving of 130–1,325 mm compared to traditional irrigation practices, accompanied by approximately 4–14% increase in tomato yield. Supplemental irrigation of maize would require 107–126 mm of water in periods of low rainfall and frequent dry spells, and 88–105 mm in periods of high rainfall and rare dry spells. Therefore, year-round irrigation may be feasible, using water saved in dry-season tomato cultivation for supplemental irrigation of maize in the rainy season. However, as predicted by the WEAP analysis, supplemental irrigation in the small-scale scheme could be possible only if the rise in water demand is counterbalanced by about 10% increase in the system efficiency and by setting limits on the cultivation of the water-intensive tomato crop in the dry season. The unavailability of long-term historical data at present prevents the calibration and validation of the WEAP model in Ghana but the conducted scenario analysis sets the framework for further evaluation of the potential water scarcity adaptation options. Overall, the integrated, whole-system approach is essential in the assessment of suitable options for improving reservoir operations and adapting to water scarcity in Sub-Saharan Africa

Year-Round Irrigation Schedule for a Tomato–Maize Rotation System in Reservoir-Based Irrigation Schemes in Ghana

Improving irrigation management in semi-arid regions of Sub-Saharan Africa is crucial to respond to increasing variability in rainfall and overcome deficits in current irrigation schemes. In small-scale and medium-scale reservoir-based irrigation schemes in the Upper East region of Ghana, we explored options for improving the traditional, dry season irrigation practices and assessed the potential for supplemental irrigation in the rainy season. The AquaCrop model was used to (i) assess current water management in the typical tomato-maize rotational system; (ii) develop an improved irrigation schedule for dry season cultivation of tomato; and (iii) determine the requirement for supplemental irrigation of maize in the rainy season under different climate scenarios. The improved irrigation schedule for dry season tomato cultivation would result in a water saving of 130–1325 mm compared to traditional irrigation practices, accompanied by approximately a 4–14% increase in tomato yield. The supplemental irrigation of maize would require 107–126 mm of water in periods of low rainfall and frequent dry spells, and 88–105 mm in periods of high rainfall and rare dry spells. Therefore, year-round irrigated crop production may be feasible, using water saved during dry season tomato cultivation for supplemental irrigation of maize in the rainy season

Biochar, compost and/or NPK fertilizer affect the uptake of potentially toxic elements and promote the yield of lettuce grown in an abandoned gold mine tailing

Background and study objectives: The low soil quality status and the high concentrations of potentially toxic elements (PTEs) found in gold mine tailings make them unfit for crop production. Assessing the possibility of mine tailings for crop production after mining is important since the presence of these PTEs harms food safety and human health. In this study, we aimed to investigate the effects of biochar, poultry litter compost, and inorganic fertilizer on the uptake of PTEs and the soil quality improvement of tailings from a decommissioned mine tailing in Ghana.Materials and methods: Rice husk biochar, poultry litter compost, and NPK were applied alone or in combination to the abandoned mine tailings at the rate of 5 t ha−1. After a 42-day pot experiment, we extracted the content of nutrients and PTEs in the soil and plant, and determined their uptake by the Lactuca sativa L.Results and discussion: Rice husk biochar, poultry litter compost and NPK applied alone or in combination significantly increased the soil pH, organic matter, available P as well as the CEC (Ca2+, K+, Mg2+, Na+) but reduced the exchangeable acidity in the mine tailings. Additionally, tailings amended with NPK increased the N uptake by 42%. Also, tailings amended with 2.5 t ha−1 biochar + 2.5 t ha−1 NPK increased both P and K uptake by 128% and 101%, respectively. For PTE uptake (i.e., Pb, Hg, As, Cd, and Cr), biochar, poultry litter compost and their combinations reduced the Hg uptake (mg kg−1) in the pot by a maximum 49% as compared to the control. Plausible formation of metal-hydroxo complexes at high pH with its consequent strong adsorption of Hg and presence of exchangeable K which contributed to the ion binding strength of the amended mine tailings reduced mobility and uptake of Hg by the lettuce. However, biochar, compost, and/or inorganic fertilizer enhanced Cd, Cr, and Pb uptake, which may pose lettuce food chain contamination problems for the inhabitants.Conclusion: As a result, we conclude that the use of inorganic NPK fertilizer and rice husk biochar can be used to improve the soil quality of abandoned gold mine tailings for safe food production, minimize Hg uptake by lettuce, and lower the associated environmental risk

Yield potentials of improved rice varieties for increased lowland rice production within the mankran watershed in Ghana

ABSTRACT Rice production in Ghana is limited by low varietal choices, which puts farmers at a disadvantage in meeting the market demand for consumers. The objectives of this study were to (i) assess the yield potentials of improved rice varieties developed by the Africa Rice Center (AfricaRice), and (ii) to allow farmers to select improved varieties of their choice based on growth and yield, as observed in the field, in order to ensure a high adoption rate, increase productivity and food security. Two seasons (i.e. 2020 major and 2020–2021 minor) field experiments were conducted at two lowland within the Mankran watershed in the Ashanti region of Ghana. The experiment comprised thirteen (13) improved varieties and two local checks and was conducted using recommended good agronomic practices. The key findings of the study showed that growth and yield parameters vary significantly between varieties across locations. The biplot analysis showed that varieties FARO 66, SAHEL 317, and Amankwatia are the best in the major season while WITA 9, GT 11, ARS-957-BGJ-171-15-D-B, NERICA L36, and AGRA were the best in the minor season at both locations. Farmers’ preference for the varieties was based not only on growth and yield but on resistance to lodging, pests, and diseases. In conclusion, the best performing varieties have demonstrated yield potential which is about 92% higher than the yield of the local checks and can be recommended for adoption by farmers. Future breeding programs on these varieties should include the most preferred attributes by farmers in this study

Increasing lowland rice yields of smallholder farmers through the adoption of good agricultural practices in the forest agro-ecological zone of Ghana

ABSTRACTRice is an important food crop in Ghana. However, its production has constantly been below 40% of the demand, and most of the requirements meet from imports. Such low production level is largely attributed to farmers’ sub-optimal crop and water management practices. As an effort toward sustainably improving rice yield, three-season on-farm participatory experiments were conducted within the Biem watershed in Ghana to determine the potential of good agricultural practices (GAP) for closing the rice yield gap with agronomic and economic sustainability. Good agricultural practices were compared with 23 farmers’ traditional practices on lowland rice growth and yield, profitability, and nutrient use efficiency. The effect of alternate wetting and drying (AWD) with GAP on grain yield of rice was also determined. Rice yield was on average 28% higher under GAP than farmers’ practices (FP). Alternate wetting and drying did not have significant effect on rice yield when compared to continuous flooding. However, when GAP was combined with AWD, rice yield was 13% higher than under FP. Furthermore, the results of the study indicate that major gains in nitrogen use efficiency (+1.48 kg grain kg−1 N; +2.4%), and net profit (+694.35 USD ha−1; +59%) were achievable through the adoption of GAP. There is therefore, a high potential to close lowland rice yield gap and achieve rice self-sufficiency through the adoption of GAP in the lowlands of the Inland valley of Ghana and similar rice production regions of West Africa