Abstract
Background and aimsEnhanced understanding of plant and nutrient interactions is key to improving yields. We adapted the model for QUantitative Evaluation of the Fertility of Tropical Soils (QUEFTS) to assess cassava yield response to soil and fertilizer nutrients in West Africa.MethodsData from on-station and farmer’s field experiments across Togo and Ghana were used.ResultsSoil nutrient supply ranged from 86 to 177, 18–24 and 70–104 kg ha−1 of N, P and K, respectively, and induced variable cassava responses to fertilizer application. Considering harvest (HI) in deriving the physiological nutrient use efficiencies for maximum dilution (PhEmax) and for maximum accumulation (PhEmin), which are key QUEFTS parameters, improved model predictions with reduction in normalized root mean square error from 32 to 13% at Davié (Southern Togo) and from 18 to 13% at Kumasi (Southern Ghana). Model overestimated yields in Nyankpala (Northern Ghana) where drought stress reduced yields. Estimated PhEmin and PhEmax at HI of 0.50 were 41 and 96 kg kg−1 N, 232 and 589 kg kg−1 P, and 34 and 160 kg kg−1 K.ConclusionsQUEFTS can be used for site-specific estimates of cassava yield responses to fertilizers under rain-fed conditions in West Africa, provided that yield is primarily constrained by N, P and K supplies, and not by drought or other nutrients.
Highlights
The differences between potential or attainable yields and actual yields, known as yield gaps, are large for cassava (Manihot esculenta, Crantz) in West Africa
The largest total N and P uptake was found in Davié (P < 0.001) and the smallest in Nyankpala, whereas the smallest K uptake was obtained in Kumasi and the largest in Davié (P < 0.001)
While the current model could be improved through further model testing experiments in other locations in West Africa and with the development of equations for estimating SAβ to cassava based on soil properties, it provides a useful tool for estimating cassava yield response to fertilizer applications
Summary
The differences between potential or attainable yields and actual yields, known as yield gaps, are large for cassava (Manihot esculenta, Crantz) in West Africa. Yields of fresh storage roots in smallholder farmers’ fields average only 11.2 Mg ha−1 (average 2000–2013) (FAOSTAT 2014), equal to about 4 Mg ha−1 storage root dry matter (DM). This yield is far less than yields of 60 Mg ha−1 (20–24 Mg ha−1 storage root DM) recorded in researcher-managed field experiments in the region (Odedina et al 2009). Accurate assessment of nutrient supplies on a site-specific basis is important for enhanced estimates of crop yields. We adapted the model for QUantitative Evaluation of the Fertility of Tropical Soils (QUEFTS) to assess cassava yield response to soil and fertilizer nutrients in West Africa. Methods Data from on-station and farmer’s field experiments across Togo and Ghana were used
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