Environmental and economic impacts of pesticide treatment in the Yam Minisett Technique

Stephen Morse

doi:10.1017/s0014479720000228

Abstract

AbstractWhite yam (Dioscorea rotundata) is an important tuber crop in a number of countries, but especially in West Africa where it serves as a food staple as well as a cash crop as excess production is sold in local markets. But the availability of quality planting material, most notably seed yams, for yam production remains an important constraint for farmers. Techniques have been developed to help address this limitation by cutting yam tubers into pieces (minisetts), treating them with the pesticide either via a seed dressing dust or pesticide ‘dips’ and planting to grow seed yams of the required size and quality. But while there have been many studies on the agronomy and adoption by farmers of these techniques, there have been fewer studies on their economic performance. Indeed, to date there have been no studies that compare the economic performance of treating setts compared to leaving them untreated, and neither has there been any analysis of the environmental impact of treating setts. This paper reports the results of a study designed to address these two gaps in knowledge and is based upon results from a series of farmer-managed seed yam plots established in the middle belt of Nigeria over 4 years (2013–2016). Results suggest that revenue and gross margin were higher for treated versus untreated setts although the latter still performed relatively well. Using the Field Use Environmental Impact Quotient (EIQ), the commonly recommended pesticide sett treatments were estimated to have a low-to-moderate environmental impact, and further research is needed to see how far pesticide use can be reduced to still be effective and minimise any environmental impact.

Highlights

White yam (Dioscorea rotundata Poir) is an important tuber crop in a number of countries, but especially in West Africa where it serves as a food staple as well as a cash crop when excess production is sold in local markets
The work of Ezeh (1991, 1998) at the National Root Crops Research Institute (NRCRI) in Umudike, Nigeria, provides perhaps the earliest and still most widely quoted cost–benefit analyses (CBA) for the Yam Minisett Technology’ (YMT), the results suggested that YMT may be uneconomic with a −0.5 return on investment and a negative gross margin:revenue ratio of −1.02
Sett treatment had a positive impact on germination rate, average tuber weight, number of tubers harvested and yield; findings that have already been well-noted in the literature (Morse and McNamara, 2018a, 2018b)

Summary

Introduction

White yam (Dioscorea rotundata Poir) is an important tuber crop in a number of countries, but especially in West Africa where it serves as a food staple as well as a cash crop when excess production is sold in local markets. Farmers are well aware of this issue and that is why they prefer to plant good quality seed yams and setts from healthy-looking tubers, and understandably the prices paid in local markets for such material can depend on the visual quality (Ibana et al, 2012). The result is that good quality planting material can be expensive, and availability may be limited. Farmers may have little choice than to plant their own saved material, even if not of the best quality. Researchers have long sought ways to address these constraints on price and availability of yam planting material, and one of the methods developed in the 1970s in Nigeria is called ‘Yam Minisett Technology’ (YMT; Iwueke et al, 1983; Orkwor and Asadu, 1998).

Methods

Results

Conclusion