This smart tech can promote water efficiency

Information on root zone moisture status gives farmers the confidence to plan their irrigation schedules and to avoid over watering

Four decades ago, I believed that plenty of water availability was central to successful farming. This belief also guided all governmental policies and practices for agricultural development. I worked on issues concerning small farmers and the focus, thus, was on digging and energising irrigation wells.

But this approach caused water levels to dip. Within a few years, the farmers were in debt. The farm yield was low since the soil was of poor quality and water had become scarce.

Soil required application of external nutrients and water shortage demanded tapping deeper aquifers, adding to the cost of farming. But, farmers did not earn proportionately to match the rise in cost.

Working in states like Andhra Pradesh, Telangana and Karnataka with small farmers, I saw thousands of peak-yield-age, high-value fruit trees drying due to lack of water availability at the right time. This caused huge economic losses and of valuable farm assets. This was also the prime trigger for farmers to commit suicide. While water remains central to farming, the quest was to how to make it available at the right time and also in a water-scarce landscape.

Under the Mahatma Gandhi National Rural Employment Guarantee Act, water conservation has the highest priority and investments. Women walk miles to fetch water to irrigate horticulture and forestry plantations.

We at Hyderabad-based non-profit Centre for Environment Concerns developed water trolleys to efficiently push 200 litres, instead of them carrying 20 litres in pots and vessels on their heads. This significantly reduced their drudgery. But the core issue of water shortage, especially in the summer months, when plant-soil thirst is high, remained unsolved.

This led us to think in terms of increasing the efficiency of water use. Indian agriculture water utilisation efficiency is 38 per cent compared to 75-80 per cent in the US.

Our quest was to innovate on technologies based on “ideal irrigation” listed by farmers in areas with scarce groundwater but horticulture crops. We looked at farmers who were already using drip irrigation to save more water as well as to use it efficiently. We wanted to further increase the water use efficiency by targeting moisture at the plant roots only.

An “ideal irrigation”, as we perceive, must increase yield per kg of produce/value per unit of applied water. We realised that water must work in conjunction with the soil’s ability to absorb, spread, retain and release it.

Drip irrigation arrived in the 1980s and is even now hailed as the “state-of-the-art” technology in water efficiency. Controlled trials showed the drip system saved up to 70 per cent of water, compared to flood irrigation.

Drip logic is “field capacity to wilting point” and it is ideal and effective for application of chemical inputs like fertilisers and pesticides. But while accounting it in terms of soil biology and microbial survival, it is not that effective a system. Excess application of chemical fertilisers and of water application led to hard soil pan and poor rainwater harvest.

India is a tropical country with rising heat waves; so shifting from water application on the soil surface to delivering moisture at the plant root zone seemed the natural way out.

So initially perforated clay pots emerged as a potential answer; but there were problems: no uniformity in size or material between batches, inability to manage water flow and breakage. It was suitable for forestry trees but in horticulture, water scarcity is detrimental to plant health and yield.

Photo: istock photo

So, we developed what is a simple add-on to drip laterals, called SWAR (System of Water for Agriculture Rejuvenation). SWAR is a low-cost buried plastic moisture diffuser with a special dripper connected to drip lateral from where the water is sent via a micro-tube into a box that contains granular cut-size quartz.

By using design software and field testing, we calculated the ideal box size, shape and height to slowly release and maximise moisture spread. It brought down water application by 40 per cent, compared to the recommendation of scientists for drip systems.

Short-run trials on vegetable crops convinced farmers of this system’s water efficacy. Some 70,000 SWAR units were sold in a few months. As recognition, SWAR won an award for innovation from the Indian Council of Agriculture Research (ICAR) in 2022.

Studies show farmers using drip irrigation over-irrigate by 65-70 per cent, compared to recommended requirements. Under SWAR, using a 12-inch (about 30 cm) portable root-zone moisture probe or by embedded soil moisture sensors, the farmers get regular updates of the root-moisture status. There is a provision for switching off and on irrigation water pump sets based on the readings of moisture sensors.

Information on root zone moisture status gives farmers the confidence to plan their irrigation schedules and to avoid over watering. One field study, carried out in an ICAR’s Krishi Vigyan Kendra in Visakhapatnam, Andhra Pradesh, shows SWAR uses 40 per cent less water application with 10 per cent higher yield in comparison to drip irrigation system. This study also shows that crops under SWAR have early fruiting, are low on weeds and high on biomass root-to-shoot ratio.

In other field trials by 10 development agencies on comparing SWAR with drip irrigation in varying soils, crops and water regimes shows it uses 40-60 per cent less water, results in 10 per cent higher yield with better crop quality, creates 25 per cent more biomass, leads to 15 per cent higher root-to-shoot ratio, requires 20 per cent less nutrient application, consumes 30 per cent less electricity and involves 70 to 75 per cent less labour cost on weed control.

In addition, as part of SWAR, we studied traditional Indian soil rejuvenation practices across states and engaged scientists, microbiologists and farmers to learn various approaches. This led us to develop “Living Compost”, a locally made microbe inoculums of available soil microorganisms, that takes four weeks to prepare.

It is an upgrade of farmyard manure coupled with select other ingredients for microbe biodiversity (for example, soil under a banyan tree) and seeding of navadanya (multiple traits of diverse native grains) to foster Mycorrhizae for root health. Living compost has improved yield.

SWAR is a directional shift, with potential to harness multiple dividends: higher yield, efficient water use with savings, healthy soils and healthy produce, consumer-centric farm gate prices to double farmer’s incomes, bio-diversity, plant resilience to drought and to tackle heat waves and climate change. Upon this foundation, farmers will build the mezzanine of their ambition to feed India, a way forward for a healthy food feast for the world, with conservation of natural resources synced to planetary well being.

(K S Gopal works with the Centre for Environment Concerns, Hyderabad)

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