An integrative approach based on crop modeling and geospatial and statistical analysis to quantify and explain the maize (Zea mays) yield gap in Ghana

Abstract

In Ghana, maize (Zea mays) is a crop crucial to achieving food and nutrition security. Maize consumption has increased exponentially over the past decades and contributes to 25% of the caloric consumption in the country. In order to assist in decision-making and guide investment in sustainable intensification of maize production, this study set out to identify the determinants of yield and to arrive at potential interventions for closing the maize yield gap. These were quantified using analytical approaches that combine a light use efficiency crop model (LINTUL-1) with statistical and geospatial analyses. Legacy data, auxiliary covariables, and maize fertilizer trials on eight experimental stations in Ghana were used in this study. Overall, the maize yield gap across the stations and trial treatments ranged from 17% to 98%. The variation in yield gap within a single station indicates a significant scope for closing the yield gap through site-specific nutrient management. Multiple linear regression models that explained 81% of the variability in maize yield gap identified soil organic matter, soil water-holding capacity, root zone depth, rainfall, sulfur fertilizer, and nitrogen fertilizer, in that order of importance, as the major determinants for closing the yield gap in the major agroecological zones of Ghana. The yield gap decreased by 1.4 t ha-1 with a 1% increase in soil organic matter. A 1 mm increase of the soil water-holding capacity reduced the yield gap by 1.06 t ha-1, while an increase in pH and in the application of potassium fertilizer widened the gap. These results suggest that both soil physical and chemical properties, together with weather data, should be taken into consideration to arrive at site-specific fertilizer recommendation and other agronomic practices.

Fertilizer use efficiency and economic viability in maize production in the Savannah and transitional zones of Ghana

“…The estimated yields in this study were lower than the yields reported by MoFA due to differences in estimation methods (Adzawla et al, 2023). Consistent with previous studies (Buah et al, 2017;Klutse et al, 2018;Adzawla et al, 2021a;Boullouz et al, 2022;Kouame et al, 2023), the use of different fertilizer formulations resulted in a significant increase in yield among the farmers. Nonetheless, the AE and PFP values estimated in this study were low at 2.0-2.9 and 13.7-18.5 kg/kg, respectively (Table 5).…”

“…This means that higher fertilizer application rates alone may not lead to improved FUE, but its use with other production practices and inputs, environmental factors, and farmer characteristics is necessary to enhance the impact of fertilizers on yields. Consistently, Boullouz et al (2022) determined that climate, soil physicochemical properties, and management practices explained a significant part of the maize yield gap in Ghana, rather than mineral fertilizers. In a meta-analysis of agronomic efficiency in SSA, Vanlauwe et al (2011) established that complementing mineral fertilizer with compost or manure results in higher nitrogen efficiency, using mineral fertilizers with improved seeds also showed significant yield gains (Martinez et al, 2023) while using local organic resources together with mineral fertilizers improves yield and its stability (MacCarthy et al, 2023).…”

“…Maize is an important crop for achieving food self-sufficiency in Ghana. Despite its economic importance and the associated high level of attention given to its production, yields remain below the potential yield (MoFA, 2021;Boullouz et al, 2022), with even the best-yielding locality in the country recording only 71.3% of the potential yield (MoFA, 2021). This has necessitated the implementation of several policies, including fertilizer subsidies, to intensify maize production in the country.…”

“…This suggests that the soils in the Transitional zone are relatively fertile and could support maize production without fertilizer, in contrast to the soils of the Guinea Savannah zone. With the huge yield gap of maize in the Guinea Savannah zone (Boullouz et al, 2022), improving the FUE can be a step toward closing the yield gaps and improving farmers livelihoods. Access to credit led to a significant increase in the FUE among the farmers, specifically in 2019.…”

“…These challenges make it difficult to maintain high yields over the long term. Meanwhile, the use of improved technologies such as improved seeds and appropriate fertilizers and farm management practices such as effective weed control can result in yields of 5-8 mt/ha or even higher for the Ghanaian maize farmer (Adzawla et al, 2021b;Boullouz et al, 2022).…”