On the Ground or in the Air? A Methodological Experiment on Crop Residue Cover Measurement in Ethiopia

Abstract

Maintaining permanent coverage of the soil using crop residues is an important and commonly recommended practice in conservation agriculture. Measuring this practice is an essential step in improving knowledge about the adoption and impact of conservation agriculture. Different data collection methods can be implemented to capture the field level crop residue coverage for a given plot, each with its own implication on survey budget, implementation speed and respondent and interviewer burden. In this paper, six alternative methods of crop residue coverage measurement are tested among the same sample of rural households in Ethiopia. The relative accuracy of these methods are compared against a benchmark, the line-transect method. The alternative methods compared against the benchmark include: (i) interviewee (respondent) estimation; (ii) enumerator estimation visiting the field; (iii) interviewee with visual-aid without visiting the field; (iv) enumerator with visual-aid visiting the field; (v) field picture collected with a drone and analyzed with image-processing methods and (vi) satellite picture of the field analyzed with remote sensing methods. Results of the methodological experiment show that survey-based methods tend to underestimate field residue cover. When quantitative data on cover are needed, the best estimates are provided by visual-aid protocols. For categorical analysis (i.e., >30% cover or not), visual-aid protocols and remote sensing methods perform equally well. Among survey-based methods, the strongest correlates of measurement errors are total farm size, field size, distance, and slope. Results deliver a ranking of measurement options that can inform survey practitioners and researchers.

Estimating adoption and impacts of agricultural management practices in developing countries using satellite data. A scoping review

“…The presence of crop residue cover is hence interpreted as direct evidence for reduced or zero tillage. Unlike estimation of zero tillage adoption, self-reported data on the extent of crop residue cover is likely to be imprecise and is often either reported as a simple binary variable or as categorical variable with broad intervals of the extent of crop residue cover (Kosmowski et al 2017).…”

“…The authors showed that SPOT-5 imagery can be used to detect crop residue cover and also stated that Sentinel-2 imagery would be a suitable replacement due to its wide swath, high temporal resolution, and higher number of bands. Kosmowski et al (2017) compared different methods of crop residue coverage measurement, including satellite imagery and household surveys. Survey data were collected from 197 households and 314 plots in Ethiopia.…”

The Rigor Revolution: New Standards of Evidence for Impact Assessment of International Agricultural Research

“…Data collection protocols for a subset of 18 research-related innovations for which background evidence suggested they had scaled were then integrated into the Ethiopian Socioeconomic Survey (ESS), a regionally and nationally representative household panel survey in 2015-2016 and 2018-2019. 3 Protocols were based on validation experiments and other measurement improvement work (Kosmowski et al 2017(Kosmowski et al , 2019 assuring that best-practice, objective, and reliable data were collected. These then yield credible estimates that between 4.1 and 11.0 million Ethiopian households had been reached by CGIAR-related innovations.…”