Are plant-soil dynamics different in pastures under organic management? A review

Abstract

Organic livestock production in the U.S. requires that a significant amount of feed comes from grazed pasture. While principles of grazing management for temperate grasslands are well known, organic livestock production may result in unique plant-soil dynamics with ramifications for farmer decision-making and management. We reviewed the literature for direct or indirect evidence that organic pasture management results in altered plant-soil dynamics and assessed whether organic management might necessitate modifications or additions to managed grazing principles. The literature directly addressing these questions is sparse. We found some evidence that organic management can stimulate soil biota but no evidence for grassland yield, soil stocks, or soil transformation rate differences between organic and non-organic pastures. Given the constraint on fertilizer and herbicide inputs in organic management, established principles of managed grazing – rotating livestock frequently through paddocks such that plants are uniformly grazed but left with significant residual biomass and time for regrowth – are critical for maintaining dense, productive swards in organic pasture management.