Organic zero-till in the northern US Great Plains Region: Opportunities and obstacles

Abstract

The use of killed cover crop mulch for weed suppression, soil erosion prevention and many other soil and crop benefits has been demonstrated in organic no-till or zero-till farming systems in eastern US regions and in Canada. Implements have been developed to make this system possible by terminating cover crops mechanically with little, if any, soil disturbance. Ongoing research in the US northern Great Plains is being conducted to identify cover crop species and termination methods for use in organic zero-till (OZ) systems that are adapted to the crop rotations and climate of this semi-arid region. Current termination strategies must be improved so that cover crop species are killed consistently and early enough in the growing season so that subsequent cash crops can be grown and harvested successfully. Delaying termination until advanced growth stages improves killing efficacy of cover crops and may provide weed-suppressive mulch for the remainder of the growing season, allowing no-till spring seeding of cash crops during the next growing season. Excessive water use by cover crops, inability of legume cover crops to supply adequate amounts of N for subsequent cash crops and failure of cover crops to suppress perennial weeds are additional obstacles that must be overcome before the use of killed cover crop mulch can be promoted as a weed control alternative to tillage in the US northern Great Plains. Use of vegetative mulch produced by killed cover crops will not be a panacea for the weed control challenges faced by organic growers, but rather one tool along with crop rotation, novel grazing strategies, the judicious use of high-residue cultivation equipment, such as the blade plow, and the use of approved herbicides with systemic activity in some instances, to provide organic farmers with new opportunities to incorporate OZ practices into their cropping systems. Emerging crop rotation designs for organic no-till systems may provide for more efficient use of nutrient and water resources, opportunities for livestock grazing before, during or after cash crop phases and improved integrated weed management strategies on organic farms.

Impacts of Organic Zero Tillage Systems on Crops, Weeds, and Soil Quality

“…Similar concerns were echoed by Mirsky et al [37] in their summary of organic ZT in northeastern USA, along with concurrence of an earlier suggestion that the vegetative mulch produced cover crops, regardless of amount, probably would not suppress established perennial weeds [26]. Cover crop mulch did suppress weeds in both the north central USA [40] and southwestern Canada [41], with dry matter production potential of selected cover crop treatments in some environments equaling and even surpassing those reported in the southeastern USA. Depletion of soil water and delays needed to ensure cover crops were killed by rolling-crimping were particular concerns when attempting to follow killed cover crops with market crops in cool dry regions [40].…”

“…Cover crop mulch did suppress weeds in both the north central USA [40] and southwestern Canada [41], with dry matter production potential of selected cover crop treatments in some environments equaling and even surpassing those reported in the southeastern USA. Depletion of soil water and delays needed to ensure cover crops were killed by rolling-crimping were particular concerns when attempting to follow killed cover crops with market crops in cool dry regions [40]. Recent performance of market crops in organic ZT systems has been mixed.…”

“…The enthusiasm generated among organic farmers spurred a growing number of researchers across North America to investigate organic ZT as an emerging cropping strategy. Results of several studies were summarized in a special issue on organic conservation tillage in Renewable Agriculture and Food Systems in 2012 [33,[37][38][39][40][41].…”

Overview of Organic Cover Crop-Based No-Tillage Technique in Europe: Farmers’ Practices and Research Challenges

“…Several papers have been published in North America on organic MBNT, summarizing the results of research trials based on cover crop species [21][22][23][24][25][26], cover crop termination methods and timing [24,[27][28][29][30][31][32][33], weed suppression [34][35][36][37][38][39][40][41], and cash crop sowing (fertilization strategies, row spacing, seeding rate) [24,42,43]. Nevertheless, in Europe, very few studies exist that focus on organic MBNT, raising questions of the effectiveness and appropriateness of this technique to enhance the sustainability of European organic farms [44].…”

“…Concerns related to the implementation of organic MBNT in Europe must be articulated to identify future research specifically addressing the implementation of MBNT on European farms. Indeed, despite the robust discussion of the challenges related to MBNT by American researchers [16,35,36,39], these challenges may differ in Europe due to its unique agricultural context (e.g., climate, information or equipment access, organic seed availability, etc. ).…”