Weed suppression and soybean yield in a no-till cover-crop mulched system as influenced by six rye cultivars

Abstract

Cover crop mulches have been successful in reducing weed severity in organic soybeans. This study examined six rye cultivars (SRCs) used as cover crops to determine which were most adapted for use with a roller-crimper in the southeastern U.S. To be an effective mulch, a rye cultivar must produce high biomass and reach reproductive growth stage to facilitate mechanical termination via the roller-crimper prior to soybean planting. Rye cultivars were planted at three locations in North Carolina over the 2009 and 2010 growing seasons. Each rye cultivar was mechanically terminated via a roller-crimper implement. Rye cover crops were terminated on two dates and soybeans were immediately no-till planted into the mulch. In 2009, all rye cultivars produced greater than 9000 kg ha −1 rye biomass dry matter (DM) with the exception of Rymin at Plymouth (2009), but in 2010 only the early flowering cultivars produced in excess of 9000 kg ha −1 DM. There were no detectable soybean yield differences between the SRCs and the weed-free checks, and weed control was excellent across all SRCs at both Plymouth and Salisbury (2009). After an unseasonably cold and wet winter in 2010, the late flowering rye cultivars were not fully controlled by the early termination date due to delayed maturation (less than 65% control at 2 WAP) whereas the early flowering cultivars were fully controlled (100% control at 2 WAP). Rye biomass production was below 9000 kg ha −1 DM for the late flowering and dough development rye cultivars. The early-terminated rye plots had greater weed coverage across all SRCs than those from the late termination date (P < 0.01). However, weeds did not impact soybean yield for either of the termination dates. Soybean yield in 2010 was modeled with rye biomass and soybean population used as covariates, and for both termination dates, soybean yield was proportional to rye biomass production. Early flowering rye cultivars offer producers the widest range of termination opportunities that best coincide with their cash crop planting dates.

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].…”

“…Indeed, some plots needed to be rolled more than once and cover crop regrowth occurred throughout the crop season, likely impacting cash crop yield [15]. According to North American researchers comparing various stages of cover crop growth and the related efficacy of termination, cover crops must reach at least the flowering growth stage to be successfully controlled [24,31,38,40]. However, the French trial experienced difficulties in delaying the sowing of the cash crop due to climate conditions which led to the cover crop being terminated prior to flowering, contributing to the failure to control the cover crop [15].…”

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

“…In particular, achieving adequate soybean seed-to-soil contact can be difficult [27]. Soil moisture can be depleted through cover crop transpiration, thereby inhibiting soybean germination [27][28][29], and soybean lodging can be problematic as hypocotyl elongation may weaken stem strength [30].…”

Reduced Tillage and No-Till in Organic Farming Systems, Germany—Status Quo, Potentials and Challenges

“…Moreover, only very few field trials with this equipment exist. A few organic farmers started only recently to use high-residue cover crops, which are killed by a roller crimper, in grain legume production in Germany, much like in North America [49,50], e.g., direct seeding of soybean (Glycine max (L.) Merr.) into cover crop residues produced by winter rye [50].…”

“…A few organic farmers started only recently to use high-residue cover crops, which are killed by a roller crimper, in grain legume production in Germany, much like in North America [49,50], e.g., direct seeding of soybean (Glycine max (L.) Merr.) into cover crop residues produced by winter rye [50]. Compared to a rolled-crimped system, which usually relies on cereals as cover crops, the diversity of cover crops is much higher in the WEcoDyn NT systems because of the frequent use of legume living mulches (e.g., white clover, Trifolium repens L.), cover crop mixtures, and/or companion cropping in the cash crops (see case studies of 42) and Wilhelm [31].…”