Inter-community and on-farm asymmetric organic matter allocation patterns drive soil fertility gradients in a rural Andean landscape.

Abstract

Soil fertility in agricultural landscapes is driven by complex interactions between natural and anthropogenic processes, with organic matter (OM) inputs playing a critical role. Asymmetric allocation patterns of these resources among communities and within individual farms can lead to soil fertility gradients. However, the drivers and consequences of such patterns in different socioecological contexts remains poorly documented and understood. The objective of this study was to address this gap by assessing asymmetric OM allocation patterns and the associated consequences for soil fertility management in three indigenous communities located in the Central Ecuadorian Andes. We found that both distance from homestead and perception of fertility were associated with asymmetric OM allocation patterns to fields as well as with soil fertility gradients within farms. For example, soil organic carbon (SOC), total nitrogen (N), available phosphorus (P), and exchangeable potassium (K) all decreased with distance from the homestead, while SOC, total N, and available P were positively correlated with a farmer's perception of soil fertility. We note that these fertility gradients remained even in the case of increased farm-level OM inputs. Overall OM allocation patterns differed significantly among communities and were associated with significant differences in soil fertility, with the highest levels of available P and exchangeable K found in the community with the highest OM inputs. The results of this study indicate the importance of asymmetric OM allocation patterns encountered at different scales, both within farms and among neighboring communities, in rural Andean landscapes and their significant interactions with soil fertility gradients.