Research Publications

A quick overview of recent VIA research publications

Soil water sensors that display colours as thresholds for action

Authors: Richard Stirzaker & Matthew Driver

Published: 3 April 2024

This paper presents a suite of simplified soil water and solute monitoring tools that give output as colours, which are thresholds for action. Data is presented as colour patterns, which highlight water and solute dynamics, such as under and over irrigation, nitrate leaching and salt accumulation. Colour is a universal language that connects the knowledge domains of scientists and farmers into a unified learning system. Evidence from the field shows that smallholder farmers using these monitoring tools can interpret the colour patterns, leading to increased yields, savings in water and a reduction in conflict on irrigation schemes.

Open access article

The role of soil water monitoring tools and agricultural innovation platforms in improving food security and income of farmers in smallholder irrigation schemes in Tanzania

Authors: M. Mdemu, L. Kissoly, H. Bjornlund, E. Kimaro, E. W. Christen, A. van Rooyen, R. Stirzaker & P. Ramshaw

Published: 30 June 2020

Smallholder irrigation is an important pathway towards better livelihoods and food security in sub-Saharan Africa. This article assesses the contribution of farmer-friendly soil and water monitoring tools, and agricultural innovation platforms, towards household income and food security in two small-scale irrigation schemes in Tanzania. Quantitative and qualitative data from farmer’s field books, household surveys and focus groups were used to assess the impacts of the two interventions. The two interventions together contributed to enhancing smallholders’ food security and household income in the two schemes, as did the agricultural innovation platform on its own.

Open access article

Do agricultural innovation platforms and soil moisture and nutrient monitoring tools improve the production and livelihood of smallholder irrigators in Mozambique?

Authors: M. Chilundo, W. de Sousa, E. W. Christen, J. Faduco, H. Bjornlund, E. Cheveia, P. Munguambe, F. Jorge, R. Stirzaker & A. F. van Rooyen

Published: 18 June 2020

Over four years, a research-for-development project was implemented at the 25 de Setembro irrigation scheme in Mozambique. The project introduced agricultural innovation platforms to overcome barriers to production such as input and output supply chains and poorly maintained irrigation canals. Soil moisture and nutrient monitoring tools were provided so that farmers could improve their irrigation and fertilizer management. The farmers increased their crop production through the use of the tools and better irrigation infrastructure, and increased their income and overall well-being through better links to markets and new information sources facilitated by the agricultural innovation platforms.

Open access article

The dynamics between irrigation frequency and soil nutrient management: transitioning smallholder irrigation towards more profitable and sustainable systems in Zimbabwe

Authors: Martin Moyo, André Van Rooyen, Henning Bjornlund, Karen Parry, RichardStirzaker, Thabani Dube & Mthulisi Maya

Published: 21 May 2020

Successful irrigated agriculture is underpinned by answering two critical questions: when and how much to irrigate. This article quantifies the role of the Chameleon and the Wetting Front Detector, monitoring tools facilitating decision-making and learning about soilwater- nutrient dynamics. Farmers retained nutrients in the root zone by reducing irrigation frequency, number of siphons, and event duration. Water productivity increased by more than 100% for farmers both with and without monitoring tools. Transitioning smallholder irrigation systems into profitable and sustainable schemes requires investment in technology, farmers and institutions. Importantly, technologies need embedding in a learning environment that fosters critical feedback mechanisms, such as market constraints.

Open access article

A soil water and solute learning system for smallscale irrigators in Africa

Authors: Richard Stirzaker, Ikenna Mbakwe & Nuru Ressa Mziray

Published: 19 May 2017

Better yields of high-value crops are necessary for a profitable irrigation industry in sub-Saharan Africa. We introduced two simple tools, the Chameleon soil moisture sensor and the Full Stop wetting front detector, which represent soil water, nitrate and salt levels in the soil by displaying different colours. These tools form the basis of an experiential learning system for small-scale irrigators. We found that farmers quickly learned from the tools and changed their management within a short time. The cost of implementing a learning system would be a small fraction of that of building or revitalizing irrigation schemes.

Open access article

Factors Affecting Sensitivity of Wetting Front Detectors

Authors: Richard Stirzaker

Published: 2008

Wetting Front Detectors (WFD) are simple instruments that provide a yes/no response when a front of certain strength passes a set depth. This paper describes two different designs of wetting front detector and determines their sensitivity under experimental conditions. The FullStop WFD comprises a specially shaped funnel that distorts the downward flow of water through the soil, producing saturation at its base. The sensitivity was determined by applying water via intermittent misting at rates of 0.1 to 0.8 mm/h. For the soil type under study, the minimum flux at which water was collected by the WFD was 0.2 mm/h. The experiment was repeated for drip irrigation, and the FullStop WFD collected water at application rates less than 0.05 L/h, corresponding to a soil suction of about 2 kPa. Whereas these application rates are lower than what can physically be applied in the field, wetting fronts do weaken with depth and time after the irrigation is turned off. Fronts can then move at rates below 0.2 mm/h or suctions drier than 2 kPa, which could go undetected.

Open article