Valuing increased zinc (Zn) fertiliser-use in Pakistan

Use of zinc (Zn) fertilisers may be cost-effective in increasing crop yields and in alleviating dietary Zn deficiency. However, Zn fertilisers are underutilised in many countries despite the widespread occurrence of Zn-deficient soils. Here, increased Zn fertiliser-use scenarios were simulated for wheat production in Punjab and Sindh Provinces, Pakistan. Inputs and outputs were valued in terms of both potential yield gains as well as health gains in the population.

The current dietary Zn deficiency risk of 23.9 % in Pakistan was based on food supply and wheat grain surveys. "Disability-adjusted life years (DALYs) lost" are a common metric of disease burden; an estimated 245,000 DALYs y^-1 are lost in Punjab and Sindh due to Zn deficiency. Baseline Zn fertiliser-use of 7.3 kt y^-1 ZnSO₄.H2O was obtained from published and industry sources. The wheat area currently receiving Zn fertilisers, and grain yield responses of 8 and 14 % in Punjab and Sindh, respectively, were based on a recent survey of >2500 farmers. Increased grain Zn concentrations under Zn fertilisation were estimated from literature data and converted to improved Zn intake in humans and ultimately a reduction in DALYs lost.

Application of Zn fertilisers to the area currently under wheat production in Punjab and Sindh, at current soil: foliar usage ratios, could increase dietary Zn supply from ~12.6 to 14.6 mg capita ^-1 d^-1, and almost halve the prevalence of Zn deficiency, assuming no other changes to food consumption. Gross wheat yield could increase by 2.0 and 0.6 Mt. grain y^-1 in Punjab and Sindh, respectively, representing an additional return of US$ >800 M and an annual increased grain supply of 19 kg capita ^-1.

There are potential market- and subsidy-based incentives to increase Zn fertiliser-use in Pakistan. Benefit-Cost Ratios (BCRs) for yield alone are 13.3 and 17.5 for Punjab and Sindh, respectively. If each DALY is monetised at one to three fold Gross National Income per capita on purchasing power parity (GNI_PPP), full adoption of Zn fertiliser for wheat provides an additional annual return of 405-1216 M International Dollars (I$) in Punjab alone, at a cost per DALY saved of I$ 461-619.