Pioneering Indian Study Highlights “More Crop Per Drop” from Fertigation
By 2050, an estimate 52 percent of the world’s projected 9.7 billion people will live in water-stressed regions, according to researchers from MIT. To feed the extra 3 billion people, 56 percent more food than was produced in 2010 will also need to be grown on existing farmland by then.
So how can we sustainably grow enough food in a changing climate while radically reducing the use of precious resources such as water and minimizing nutrient losses to the environment?
The answer may well be through fertigation: applying fertilizers dissolved in water through precision irrigation systems which allows plants to receive water and nutrients in precise amounts and locations at the same time.
A recent CIMMYT study in India found that sub-surface drip fertigation systems combined with conservation agriculture approaches such as zero till, retaining residues on soil surface and dry seeding, could be used to grow rice and wheat using at least 40% less water than flood irrigation for the same amount of yields while also using 20% less urea.
The study has helped emphasize some of the numerous benefits of fertigation: effectively improving the yield and quality of crops, as well as allowing farmers to grow produce on marginal soils with limited amounts of water and a reduced environmental footprint. By using partially treated wastewater, the technique can also help turn waste into a resource.
By allowing fertilizer applications rates to be dosed according to plant uptake rates, distributing nutrients directly to the root zone, and maintaining a constant level of low but accessible nutrients in the soil solution, the technique can produce up to 90% nutrient use efficiency.
Thanks to the combination of precise amounts of nutrients with small amounts of water, fertigation can also reduce nitrogen run-off by up to 70 percent compared to other fertilizer application methods, while also needing up to 50 percent less fertilizers to produce the same yields.
With a quarter of the world’s population across 17 countries already living in regions of extremely high water stress, according to the World Resources Institute, there seems to be a pressing need to use fertigation to help grow enough food in many parts of the world including in India, the Middle East and North Africa.
While fertigation is already widely used in some areas, such as in 80% of Israel’s 200,000 ha of irrigated land, with the right infrastructure already in a considerable amount of farmland, there are significant opportunities for wider scale adoption.
The last 20 years have seen an astonishing growth in the use of increasingly sophisticated irrigation systems, helped by substantially falling costs. With up to 95% water use efficiency allowing farming even in areas with water shortages, the total area cultivated by low water pressure and flow micro-irrigation systems has risen from 1.1 million ha in 1986 to around 11.1 million in 2015.
Much of the world’s irrigated land still use practices that are not suitable for effective fertigation, however, such as flood irrigation. Although irrigated land represents about 37% and 34% of the total arable land of China and India, for example, micro-irrigation is estimated to only be practiced on 0.6% and 2% of their arable land respectively.
Despite its numerous benefits, managing the potentially complex combination of nutrient and water supply can make fertigation a challenging technique. To meet crops’ fertilizer needs while minimizing losses, growers must accurately estimate crop nutrient requirements, soil nutrient availability and ensure the delivery of nutrients as well as water at the right times.
Luckily, technology is helping to make fertigation easier and more efficient. A growing range of optical, multispectral and soil-based sensors can measure plant stress in addition to nutrient content both in the canopy and at the root zone.
This data can then be fed to smartphone-based decision support systems apps, which also use algorithm-based modeling to give advice on crops’ water and fertilizer requirements tailored to specific areas in a field, with intelligent automated delivery systems administering the results.
Such high-tech solutions remain expensive, however, while even drip irrigation systems themselves can often be inaccessible to many farmers, particularly in off-grid environments where they can cost more than $1,200 per hectare to install (though subsidies are operating in a number of countries including India).
Recent advances could help drive down those costs however; by optimizing the drippers, in 2017 engineers at MIT found a way to cut the cost of solar-powered drip systems by half, for example. The falling costs of sensors, processors and smartphones should also make automated fertigation systems more affordable.
As the recent CIMMYT study has highlighted, fertigation has huge benefits throughout the developing world. As climate change continues and water stress increases, governments, NGOs and the private sector should focus on further establishing micro-irrigation and fertigation.
To help feed the world and smallholders thrive, the future of sustainable agriculture looks increasingly fertigated.