Nitrogen Delivery from Legume Cover Crops in No‐Till Organic Corn Production

Abstract

Sixteen winter annual cover crop cultivars were grown in North Carolina to determine total N accumulation, biological N fi xation (BNF) potential, and compatibility with a roller-crimper-terminated organic corn (Zea mays L.) production system. Cover crops and termination dates were tested in a stripped block design. Treatments included hairy vetch (Vicia villosa Roth), common vetch (Vicia sativa L.), crimson clover (Trifolium incarnatum L.), Austrian winter pea (Pisum sativum L.), berseem clover (Trifolium alexandrinum L.), subterranean clover (Trifolium subterraneum L.), narrow leaf lupin (Lupinus angustifolius L.), and Balansa clover (Trifolium michelianum Savi.), as well as bicultures of rye (Secale cereale L.), hairy vetch, and Austrian winter pea. Roller-crimper termination occurred in mid-April, early May, and mid-May. Total biomass, N concentration, and C/N ratios were determined for cover crops at all roll times and natural 15 N abundance at the optimal kill date. Hairy vetch and crimson clover monocultures had the greatest overall biomass in 2009, and bicultures the greatest biomass in 2010. Crimson clover successfully terminated in late April, hairy vetch and Austrian winter pea in mid-May, and berseem clover and common vetch in late May. All cover crops except lupin and subterranean clover derived between 70 and 100% of their N from the atmosphere. Corn response to cover crop mulches was signifi cantly aff ected by the time of rolling, with poor stands resulting from competition with insuffi ciently terminated mulches. Crimson, Balansa, and subterranean clover mulches resulted in poor corn yields despite relatively high levels of total N. Th e highest corn yields were achieved in hairy vetch and rye plus hairy vetch bicultures.

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].…”

“…While legume cover crops increase N supply to the subsequent corn crop, legume species are also more difficult to terminate through rolling and experience less effective weed control due to their faster residue degradation rate (low C:N rate) and lower biomass production as compared to cereal species. This lack of cover crop biomass on the soil surface throughout corn production season could explain the failure observed in the French trial [15] with alfalfa, as well as the interest of some North American researchers to use cover crop mixtures composed of both legume and cereal species prior to corn MBNT [75]. Cereal species could reduce the amount of N supplied to corn; however, this hypothesis must be further tested to obtain a better understanding of N dynamics in MBNT production.…”

Cover Crop-Based, Organic Rotational No-Till Corn and Soybean Production Systems in the Mid-Atlantic United States

“…Improved cover crop germplasm, including the development of highly adapted regional varieties [72], would allow for greatly improved integration and management of cover crops within existing cropping systems, particularly as they relate to cover crop phenology and termination timing [21,29]. Greater standardization of leguminous cover crops would aid the development of more reliable N management recommendations and advance our ability to predict how fixed N contributes to subsequent corn yield [73], particularly when legumes are grown in mixtures with grasses. More research is also required to understand the allelopathic properties of cover crops and how they can be effectively managed to maximize weed suppression while minimizing negative impacts on cash crops.…”

Plant species and mulch application rate affected decomposition of cover crop mulches used in organic rotational no-till systems

“…Many questions remain unanswered about the synchrony of N release from mulches with the subsequent crop N requirements and possible N losses or immobilization in these reduced-tillage systems. Researchers have started to investigate the N contribution of rolled mulches in North America (Parr et al 2011;Brown 2013;Wells et al 2013), but studies on N dynamics in organic no-till systems are scarce.…”