|Carr, Patrick -|
|Gramig, Greta -|
Submitted to: Sustainability
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 15, 2013
Publication Date: July 22, 2013
Citation: Carr, P.M., Gramig, G.G., Liebig, M.A. 2013. Impacts of organic conservation tillage systems on crops, weeds, and soil quality. Sustainability. 5:3172-3201. Interpretive Summary: Research on adoption of conservation tillage to organic farming has expanded from a limited effort in the early 1990s to involve numerous research teams in both North America and Europe. Moreover, field studies no longer are confined to these two continents but have expanded globally. Progress is being made to reduce and, in some instances, eliminate tillage completely when certain field and horticultural crops are grown organically. Several potential agronomic, weed management, and soil quality benefits result if adoption of conservation tillage practices is successful in organic production systems. However, much work remains before these systems can be effectively implemented in a consistent manner. Research needs to improve organic conservation tillage systems include 1) a better understanding of the role of cover crops in these systems, with particular focus on their selection, management, and termination, 2) effective supplementary weed control options, such as livestock grazing or low-disturbance mechanical weed or weed seed destruction, and 3) more rigorous soil quality assessments.
Technical Abstract: Organic farming has been identified as promoting soil quality even though tillage is used for weed suppression. Adopting conservation tillage practices can enhance soil quality in cropping systems where synthetic agrichemicals are used for crop nutrition and weed control. Attempts have been made to adapt conservation tillage practices to production systems managed organically. Success has occurred when eliminating tillage during specific crop phases within a rotation, but refinement is needed before zero tillage, crop phase organic farming can be implemented successfully in a consistent manner. With this as context, recent literature was compiled and synthesized addressing agronomic, weed, and soil quality impacts associated with organic conservation tillage systems. Previous research has provided base-line data on the quantity of cover crop residue needed to suppress annual grass and broadleaf weeds in organic conservation tillage systems, but considerable work is required to answer a host of basic agronomic questions related to cover crop species adaptation and selection, management for maximum above-ground dry matter production, and termination method for timely and effective kill with minimum soil disturbance. Developing more effective supplementary weed control options, such as livestock grazing or low-disturbance mechanical weed or weed seed destruction, may enhance the feasibility of organic conservation systems. Much research examining effects of tillage intensity on weed population dynamics and soil attributes has been conducted in conventional systems, where the application of agrichemicals represents a strong filter on the assembly of biotic communities including weeds and soil macro- and microfauna. Outcomes synthesized from a limited number of short-term studies suggest organic conservation tillage systems create a soil environment with improved nutrient cycling capacity, though it is unclear if the long-term application of these systems mitigates soil degradation concerns associated with organic farming. Collectively, additional research addressing agronomic, weed, and soil quality responses to conservation tillage is needed under organic management conditions.