Variability in soybean yields, nutrient use efficiency, and profitability with application of phosphorus fertilizer and inoculants on smallholder farms in sub-Saharan Africa

Abstract

Summary Although soybean is emerging as an important commercial crop in sub-Saharan Africa (SSA), its productivity on smallholder farms is very low. Soybean requires application of phosphorus (P) fertilizer and inoculation with the right rhizobium strains to achieve optimum biological nitrogen fixation and higher yields. However, subsistence farmers in SSA rarely invest in P fertilizers and inoculants due to lack of knowledge of their use and benefits. Most of the early reports on soybean in SSA have been based on work on research stations; hence, information is lacking on the profitability of fertilizer and inoculant use on smallholder farms in SSA. The main hypothesis of the present study was that the combined application of P and inoculants significantly reduces yield risks and increases P use efficiency and profitability compared with P fertilizer alone under smallholder farm conditions. We analyzed a data set of over 2,800 observations from on-farm demonstrations across Ghana, Kenya, Malawi, Rwanda, Tanzania, Uganda, and Zambia. Soybean yields, the partial factor productivity of P (PFPP), agronomic efficiency of P (AEP), and the value cost ratio (VCR) were significantly improved by the combined application of P fertilizer with inoculants than with P fertilizer alone. Combining P and inoculants increased yields over P alone by 17.3% in Kenya, 21.4% in Zambia, 25.7% in Ghana, 56.4% in Tanzania, and 57.1% in Malawi. However, soil organic matter was an important determinant of yield response and P use efficiency. The VCR increased linearly with increasing AEP in P + inoculant (R2 = 0.829) and less so with P fertilizer alone (R2 = 0.672). Net present values were positive in all countries, indicating that investments in P fertilizer and inoculants will generate profits over time. In order to increase uptake of fertilizers and inoculants among subsistence farmers and make soybean production more profitable, appropriate policies and market incentives need to be created.

Influence of phosphorus fertilizers on the yield of soybean varieties in the conditions of Uzbekistan

“…The area of each plot was 72.0 m 2 . The experiments were performed in a field and laboratory manner using "Methods of conducting field experiments" [3], "Methods of field experiments" [4], "Methods of state agricultural research" [5][6][7], and "Agricultural agrochemical methods" [3,7,12] methods.…”

“…Soy is a plant demanding to nutrients. 124 kg of nitrogen, 22 kg of phosphorus, 102 kg of potassium, 34 kg of calcium, 23 kg of sulfur, 191 g of zinc, 18 kg of magnesium, 207 g of manganese, 865 g of iron and 75 g of copper are extracted from the soil to a grain yield of 24 q/ha per hectare [6][7][8]. The absorption of macronutrients during the period of shadow application is not uniform.…”

“…The absorption of macronutrients during the period of shadow application is not uniform. According to one group of scientists, 80% of phosphorus and 50% of potassium are absorbed during the flowering period, and the rest is absorbed during the ripening phase of the grain [6,7]. It is found that from soybean weeding to the flowering period, nitrogen is 5.9-6.8%, phosphorus is 4.6-4.7% and potassium is 7.6-9.4% [9,10].…”

Predictors of inoculant-based technology adoption by smallholder soybean farmers in northern Ghana: implications for soil fertility management

“…In terms of economic benefit, they recorded a value cost ratio of 8.7, which is a measure of returns on investment. Asei et al [6] also recorded a 67% increase in soybean grain yield in a study in northern Ghana, while Kiwia et al [16] reported that combining phosphorus fertilizer with inoculants increased soybean yield over phosphorus fertilizer alone by 25.7%. In another study, Nabintu et al [22] examined farmer' perceptions about rhizobium inoculants in the Democratic Republic of Congo and found that farmers generally perceive higher productivity and cost efficiency of rhizobium but were challenged with its consistent unavailability at the market.…”