Assessment of measures to reduce the water footprint of cotton farming in India.

Published online
05 Oct 2016
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Pahlow, M. & Krol, M. S. & Hoekstra, A. Y.
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Based on the findings presented in this report, general recommendations regarding measures and strategies to decrease the water footprint (WF) of cotton production can be provided. Given that the grey WF is generally much larger than the consumptive WF, reduction of the grey WF has priority over reduction of the consumptive WF. Yet India has diverse agro-ecological zones and therefore it must be noted that region-specific measures and strategies are essential to achieve best benefit. The zones deviate in climate, soil type and financial means from each other, hence suitability and feasibility of implementation of a certain measure may differ for a given location. There are certain measures that can be termed 'no regret' options, as they require little or no additional investment, yield reduction is not probable and they have WF reduction potential. To that end, pesticides that result in a large grey WF should be replaced with substances that target the same pest(s), are effective, but lead to a WF reduction. Crop rotation has a positive effect on soil fertility and supports pests control. Application of nutrients can be optimized and potentially reduced after determination of actual soil fertility and a sequential adjustment of the amount of fertilizer applied. Furthermore, the amount of nutrients may partially be replaced with organic and locally available replacements such as farmyard manure without sacrificing yield. Mulching with available crop residue is an effective means to reduce evaporation and at the same time may increase yield. Intercropping is very efficient to that end, as the intercrop shades the soil, provides additional yield and crop residue for additional mulching and soil improvement. Field runoff should be reduced through measures such as field levelling, cropping on contour in sloping terrain or a ridge and furrow system. Application of irrigation water can be reduced by applying a deficit irrigation strategy, whereby water is provided at less than full irrigation and at those times where water is most critical for crop growth (flowering and boll formation). Note that in the case of rain-fed farming supplemental irrigation in incidental drought periods is highly effective. Best management practices include, but go beyond the 'no regret' options and may require substantial investment and adequate training of the farmers. These involve the selection of cultivars best suited for the production region, innovative and sustainable cotton-based cropping systems and precise water and fertilizer application systems. In short, the grey WF can be most effectively reduced through organic farming, whereby precision application of water and nutrients (fertigation) is implemented, when compared to conventional farming. The major trade-off may be lower yield, thus larger consumptive WF, at least in the short term. However, in the long term this effect may be small. The consumptive WF can be reduced most effectively by implementation of the following agronomic measures: mulching (organic or, even more effective, synthetic mulching); efficient irrigation technology (with sub-surface drip irrigation resulting in the smallest consumptive WF, followed by drip irrigation, furrow irrigation and finally sprinkler irrigation); a deficit irrigation strategy (reducing field evapotranspiration by 20-40% compared to full irrigation); and precision irrigation in time and space (irrigation scheduling and variable rate irrigation). In the short term it is recommended to aim at implementation of no-regret measures in conventional cotton farming, creating market support for organic cotton and developing a capacity building and investment programme to help farmers switch to conservation agriculture. In the long term it is recommended to strive for a transition to less pesticide-intensive agronomic practices. This leads to direct and substantial reduction of the grey WF. The consumptive WF can be reduced significantly through best management practices.

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