Wetting Front Detector

Summary

Farmers need information about water and nutrients in their soil.  Water scarcity, both real and perceived, fuels conflict and undermines attempts to equitably govern and share water.  The Virtual Irrigation Academy Ltd (VIA) has developed the Wetting Front Detector (WFD) solute monitoring system which provides simple information about the depth of water penetration in the soil and key solutes. VIA has deployed over 30,000 WFDs to date and most farmers have reduced water use and increased productivity through its use.
 

Challenge/Problem

Irrigated agriculture is going to have to feed an ever-increasing proportion of the world’s growing population - but supplies of fresh water are dwindling.  Much of the increase in food production will need to come from smallholder farmers in rural areas of Low- and Middle-Income Countries (LMICs), where approximately 80% of the population relies on the Agri-Food system for their livelihoods. Improving small-scale farming in these countries will contribute to the alleviation of poverty, hunger, youth unemployment and forced migration for millions.  The combined challenges of climate change and water scarcity mean that new solutions need to be implemented to help smallholder farmers increase their food production in an environmentally sustainable way. Farmers need information about the water and solutes in their soil. Without information, farmers adopt the low-risk approach of adding water and fertiliser, even when it may not be needed, which leads to problems such as waterlogging, salt build-up and nitrate leaching.   Knowing the depth of soil water and levels of key solutes allows farmers to carefully manage irrigation to avoid these problems.  However, this is not just a tech-fix problem. Growing more food with less water is a people problem and this information needs to be easily accessible and readily shared to ensure fair and equitable water use among farming communities. 

Solution

The Wetting Front Detector (WFD) is a 200 mm diameter funnel-shaped instrument. A hollow tube containing light-weight floats runs through the centre of the funnel and has a pop-up indicator on top. The indicator shows when a water sample has been collected.  The WFD is used to indicatehow deep irrigation water has infiltrated into the rootzone. It is also useful as a device to measure what is dissolved in the soil water. The WFD captures a soil water sample which is extracted using a syringe for monitoring of salt and nitrate in the root zone.  Nitrate strips and EC meters are provided as part of the monitoring system.

Nitrate is essential for rapid plant growth. Unlike other soil nutrients, nitrate does not ‘stick’ to the soil particles. Nitrate moves together with the water, so over-irrigation will result in loss of nitrate and lower yields.  It is important to know the quality (EC) of irrigation water. If irrigation water is in the green zone, then salt build up is not usually a problem, unless there is waterlogging or rising groundwater.

The WFD can be used as a standalone system or in combination with the Chameleon sensor.

On Koga irrigation scheme in Ethiopia, 216 farmers were provided with WFDs. Through use of this solution farmers were able to reduce water use by one third and have 10-20% increase in yield. In addition to provision of WFDs, the project provided training to an additional 400 farmers on the scheme. The farmers who received WFDs were encouraged to share the information from the products with their fellow farmers.  This information exchange helped improve water use and yields on all farms and overall water management on the scheme.

Results

To date VIA has built and deployed over 30,000 WFDs, primarily in sub-Saharan Africa and Pakistan. The charity has collected information from hundreds of farmers who have used the products and the results are overwhelmingly positive:

- 20% increase in yields compared to control plots or prior seasons

- Irrigation scheme in Ethiopia saw median yield for wheat increase from 2.2t/Ha for control plot to 2.8t/Ha for WFD plot

- Irrigation scheme in Mozambique with 38 farmers saw average green maize yield increase from 5.3t/Ha to 16t/Ha after introduction of the tools

- 33% reduction in water use compared to control plots or prior seasons

- Irrigation scheme in Ethiopia saw median water application for wheat reduce from 562mm for control plot to 369mm for WFD plot

- 35% increase in water productivity (crop per drop)

Specific project or country examples include:

1. Koga irrigation scheme in Ethiopia where 216 farmers used WFD. Farmers saw an average of 35% reduction in irrigation and up to 20% increase in yield when compared to control plots.
2. Wagrinnova project in Ghana where 190 farmers used WFDs. Farmers reduced irrigation by between 13% and 65% and a 37% increase in efficient water use by crop compared to prior seasons.

Lessons Learned/Potential for replication

During implementation, farmers quickly made the link between over irrigation and leaching of nutrients from the soil.  We learned that farmers knew they were likely over irrigating but lacked the information needed to change practice.   Another important lesson discovered during user deployment was the social and community value of the information provided by the solution.  Farmers using the product were very willing to share their information with their friends and neighbours, spreading the benefits beyond product users and helping to bring about community level impacts like reduced conflict and better overall management of water resources.

Building local knowledge and in-country capacity is key for building trust, so farmers and stakeholders understand how the products work, and how to troubleshoot and carry our repairs and maintenance.  The WFD has the potential to benefit between one and two hundred million of the poorest farming households in the world.

Next Steps

Irrigation is going to be a major part of adapting to climate change and most of this is going to have to be on small farms in low-income countries. Our technology is designed for these farmers and has been shown to work.  VIA believes that information systems for sustainable water management and productivity should be used by all irrigation farmers.  We are seeking to partner with governments and NGOs across LMICs who are deploying, or have deployed, irrigation infrastructure to smallholders.  Use of Wetting Front Detectors has been proven to improve ROI on public/donor irrigation infrastructure projects.