Soil Fertility Experiments

The importance of soil health in achieving food security targets and eradicating poverty has been recognized in the development community, exemplified by the UN General Assembly’s declaration of 2015 as the International Year of Soils. The recent increase in attention paid to soil health is for naught, however, if soil health measurements are inaccurate or of inadequate resolution.

Much of the current analysis on agricultural productivity is hampered by the lack of consistent, high quality data on soil health and how it is changing under past and current management. This is especially critical in the face of increased variability in weather conditions brought on by climate change. Renewed interest in increasing agricultural productivity to meet food security needs and increasing resilience of agricultural systems in developing countries, especially in sub-Saharan Africa, makes understanding soil fertility constraints and trends ever more important.

The LSMS team, with support from UK Aid and in collaboration with the World Agroforestry Centre, has prioritized the methodological validation of various approaches to collecting high quality soil health data in household surveys. Historically, household surveys have relied on subjective assessments of soil fertility. However, objective measurement methods for soil analysis have experienced technological advances in recent history. New, rapid low cost technology for assessing soil characteristics using infrared spectroscopy has made soil fertility evaluations feasible in large studies (Shepherd & Walsh, 2002; 2007).

The LSMS team has set out to pilot the use of soil spectroscopy alongside traditional methods in order to determine (a) the trade-offs between data quality and resource requirements, (b) systematic differences across methods, and (c) the feasibility of implementing these methods in future national household surveys. To date, experiments have been conducted in Ethiopia and Uganda.


Ethiopia Land and Soil Experimental Research (LASER) In an effort to improve the quality of agricultural data, particularly with respect to land area and soil fertility measurements, the LSMS team collaborated with the Central Statistical Agency of Ethiopia and the World Agroforestry Center (ICRAF) to execute the Land and Soil Experimental Research (LASER) study in Ethiopia.

The LASER study aimed to test the methodological options in measuring land area and soil fertility and subsequently assess the feasibility of implementing each method in large household survey operations. Methods tested for land area measurement include traversing (or compass and rope), handheld GPS unit, and farmer estimation. Plot-level soil samples were collected and analyzed at ICRAF’s Soil-Plant Spectral Diagnostics Laboratory using conventional and spectral techniques. Additionally, a series of subjective questions were asked of the farmer to allow for comparison of subjective and objective measurements of soil fertility.

Crop-cutting was conducted on pure stand maize fields. LASER was implemented across three administrative zones of the Oromia region in Ethiopia. In total, 1018 households were interviewed, with nearly 1800 agricultural fields selected for objective land area and soil fertility measurement.