Yield gap analysis and resource footprints of Irish potato production systems in Zimbabwe

tIrish potato is the third most important carbohydrate food crop in Zimbabwe after maize and wheat. In2012, the Government of Zimbabwe declared it a strategic national food security crop. In this study, weexamine the country’s potential for increasing Irish potato yield and help ease the nation’s food secu-rity challenges. The magnitude of food production increase on already existing croplands depends onthe difference between the current actual yields and the potential yield of the crop in the given agro-ecological environment, also called the yield gap. We used three already well-understood types of yieldgap: (1) the gap between actual farmer yields, Ya, and the maximum (potential) yield, Yp, achieved whena crop is grown under conditions of non-limiting water and nutrient supply with biotic stress effectivelycontrolled; (2) the gap between Yaand the water-limited yield, Yw, which is the maximum yield attain-able under rainfed systems; and (3) the gap between Ya, and the highest yield, Yh, achieved by the bestfarmers in an agro-ecological area. A grower survey was conducted on the different potato productionsystems in the country in order to establish the actual yields and input application rates used in potatoproduction. The actual potato yields were used to calculate efficiencies of natural and synthetic resourcesuse. Potential and water-limited yields, and planting times of potato were established for the differentagro-ecological regions using the LINTUL-POTATO model, a model based on interception and utilisationof incoming solar radiation. The mean actual yield observed ranged from 8 to 35% of the potential yield,translating to a yield gap of 65 to 92%, hence there is a huge potential to increase production. Simu-lated potential water use efficiency based on evapotranspiration range was 19–27 g potato/l against theactual water use efficiency of 2–6 g potato/l based on irrigation and rainfall. The current high fertiliserapplication rates and low actual yields we report, suggest inefficient fertiliser use in potato productionin Zimbabwe. The average actual fungicide and insecticide use efficiencies were 0.7 and 13 kg potato/gactive ingredient, respectively, across all production systems. All sampled growers lacked knowledge onintegrated pest management, a concept which could possibly improve the biocide use efficiency throughlowering biocide application rates while maintaining or even improving yields. Our analysis suggeststhat there is opportunity to improve water, nutrients and biocides resource use efficiencies and increasepotato actual yields in Zimbabwe.

Wageningen Univer-sity and Research Centre PhD Sandwich programme (grant number318338) with additional funding from the Chinhoyi University ofTechnology (grant number RB2240) for field data collection inZimbabwe.

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hb2015