Yield gap between organic and conventional farming systems across climate types and sub-types: A meta-analysis

Abstract

Context: Organic farming is a fast-growing system considered a holistic approach that benefits the environment. However, previous studies have reported varying results on its productivity when compared to conventional farming systems. Moreover, the effect of climatic conditions on the yield gap between organic and conventional methods has not been extensively studied. Objectives: Considering the influence of temperature and precipitation on soil microbial activity that drives the decomposition of organic matter and supports the mineralization of organic matter for plants, we hypothesized that the yield gap between organic and conventional farming systems is affected by climatic conditions; that is, it should be higher in locations with warmer climates that those in colder climates. Methods: Yield data were collected from 105 studies that compared organic and conventional farming; 786 pairwise observations were extracted mainly from previous meta-analyses and individual studies. Using meta-analysis in R software, we examined the yield ratio between the two farming systems in different climate types (boreal, warm temperate, arid, and equatorial) and sub-types, and further investigated other influencing factors such as crop type, study location by region, and soil pH and texture. Results and conclusions: The yield of organic farming was 18.4% (RR = 0.83; 95% confidence interval of 0.77 to 0.89; p = < 0.0001) lower than that of conventional farming, regardless of climate condition, crop type, and other categorical variables. Results showed that only the warm temperate climate had a significant effect on the yield gap between organic and conventional farming systems, where organic yields were 21.18% lower than those of conventional farming (RR = 0.79; 95% CI 0.71 to 0.87; p = < 0.0001; k = 446). However, the variability associated with temperature and precipitation was difficult to estimate using the current data. Among the categorical variables evaluated, it was found that specific crop types, regions, and soils significantly influenced the yield gap. Additional analyses revealed a confounding crop-type effect on the yield gap that requires further investigation. Nevertheless, this study suggests that when determining variations in the yields and productivity of organic and conventional farming systems, it is critical to account for interactions between variables. Significance: The results of this study offer a preliminary understanding of how the climate type affects the yield of the two farming systems in a particular geographic location, supporting future research that will provide a quantitative context to land use development for sustainable agriculture.