Assessment of the 2006 Abuja Fertilizer Declaration With Emphasis on Nitrogen Use Efficiency to Reduce Yield Gaps in Maize Production

Abstract

The Abuja Fertilizer Declaration in 2006 recommended the increase of fertilizer use from the current practice for Sub-Saharan Africa (SSA) to achieve food sufficiency and improve soil fertility status. However, the current recommended rates of fertilizer have not been evaluated for specific crops on their potential to reduce the yield gap and optimize nitrogen use efficiency (NUE). In this study, with nitrogen (N) being a significant yield-determinant nutrient, four N use scenarios were drawn from existing recommendations and were evaluated under field conditions for maize crops in two catchments of the Lake Victoria basin. The scenarios included Business as Usual (BAU, 0 kg N ha−1), 25% of the Abuja declaration (ADS 12.5 kg N ha−1), 50% of the Abuja declaration (ADS 25 kg N ha−1), and Abuja declaration–Abuja scenario (ADS, 50 kg N ha−1). The results revealed that increasing N input levels significantly influenced the growth and yield of maize crops. The ADS scenario recorded the highest grain yield increase (167.39%) in Nyando and 103.25% in Rangwe catchments compared to the BAU scenario. N deficits were observed in all the N use scenarios with a range of −66.6 to −125.7 kg N ha−1 in Nyando and −62.5 to −105.4 kg N ha−1 in Rangwe catchments with the 50% ADS scenario having the highest deficits. The deficits imply that the added N input is insufficient to create an N balance for optimal NUE with consequent high risks of soil N mining. In both catchments, all N use scenarios were within the recommended agro-physiological N efficiency (APEN) level of between 40 and 60 kg kg−1 N. The partial N balance obtained at Nyando (1.56–3.11) and Rangwe (1.10–4.64) was higher than the optimal values, a sign of insufficiency of N inputs and possible risk of soil N depletion in all the scenarios. Our findings conclude that the proposed N rates in the region are still very low for food sufficiency and optimized NUE. Therefore, there is a need to explore other sources of N such as biological N fixation and organic manure and inform policy- and decision-makers to recommend higher rates beyond the “Abuja declaration” with the prospect of reaching target yield and optimizing NUE values based on specific crop recommendations.

A historical review of fertilizer policies in Nigeria

“…Although average consumption for Nigeria improved to 17.4 kg/ha between 2016 and 2018, this was still more than 2.5 times less than the average for SSA (44.4 kg/ha) and about 10 times less than the world average of 184.37 kg/ha (World Bank, 2018). This average is also below the recommended fertilizer application target of 50 kg/ha set for Africa by the Abuja Declaration on Fertilizer for an African Green Revolution (Maria, 2011;Tsakok, 2019;Winnie et al, 2022). Fertilizer consumption in developing countries like Nigeria has been highly dependent on government policies and programs, including subsidies that provide farmers access to fertilizer at discounted rates.…”

Influence of farmers’ socio-economic characteristics on nutrient flow and implications for system sustainability in smallholdings: a review

“…In SSA, fertilizer use is definitely very low compared to the developed world (122). Reports have shown that the average fertilizer use on crop land is 135 kgha -1 year -1 in developed countries, whereas SSA exhibits the lowest rate of less than 15 kg ha -1 year -1 (123,124). The 2006 Abuja Fertilizer Declaration estimated that by 2015 the fertilizer use in SSA could be 50 kg ha -1 of N, P, and K (123).…”

“…Reports have shown that the average fertilizer use on crop land is 135 kgha -1 year -1 in developed countries, whereas SSA exhibits the lowest rate of less than 15 kg ha -1 year -1 (123,124). The 2006 Abuja Fertilizer Declaration estimated that by 2015 the fertilizer use in SSA could be 50 kg ha -1 of N, P, and K (123). Generally, there are some efforts to increase fertilizer use in SSA countries, yet the pace is too slow to meet the target, with an average of 5 kg in 1990 and 10 kg in 2008 (122).…”

Nitrogen fertilization and liming increased CO2 and N2O emissions from tropical ferralsols, but not from a vertisol

“…In sub-Saharan Africa, farmers are highly encouraged to use N fertilizers to boost soil fertility and crop productivity (van Loon et al, 2019). The current average N fertilizer application rate is 12.5 kg N ha −1 in contrast to the recommended potential of 50 kg N ha −1 (Masso et al, 2017;Ntinyari et al, 2022). Low N input and continuous cropping without matching the crop N demand have led to widespread N mining and the depletion of soil N stocks in tropical soils (Leitner et al, 2020).…”