Rolled Winter Rye and Hairy Vetch Cover Crops Lower Weed Density but Reduce Vegetable Yields in No-tillage Organic Production

Abstract

<jats:p>Winter annual cover crops, winter rye (<jats:italic>Secale cereale</jats:italic> L.) and hairy vetch <jats:italic>(Vicia villosa</jats:italic> Roth), can reduce weed density and build soil quality in organic production systems. There is interest in integrating cover crops and reduced tillage with organic vegetable production, but few studies have been conducted in regions with short growing seasons and cool soils such as the upper Midwest. We evaluated no-tillage production of tomato (<jats:italic>Solanum lycopersicum</jats:italic> L.), zucchini (<jats:italic>Cucurbita pepo</jats:italic> L.), and bell pepper (<jats:italic>Capsicum annuum</jats:italic> L.) planted into winter rye, hairy vetch, and a winter rye/hairy vetch (WR/HV) mixture that were mechanically suppressed with a roller–crimper at two locations in Minnesota. Average marketable yields of tomato, zucchini, and bell pepper in the rolled cover crops were reduced 89%, 77%, and 92% in 2008 and 65%, 41%, and 79% in 2009, respectively, compared with a no-cover control. Winter rye and the WR/HV mixture reduced average annual weed density at St. Paul by 96% for 8 to 10 weeks after rolling (WAR) and hairy vetch mulch reduced weeds 80% for 2 to 8 WAR, whereas at Lamberton, there was no consistent effect of cover treatments on weed populations. Winter rye and the WR/HV mixture had higher average residue biomass (5.3 and 5.7 Mg·ha<jats:sup>−1</jats:sup>, respectively) than hairy vetch (3.0 Mg·ha<jats:sup>−1</jats:sup>) throughout the season. Soil growing degree-days (SGDD) were lower in cover crop treatments compared with the no-cover control, which could have delayed early vegetable growth and contributed to reduced yields. All cover crop mulches were associated with low levels of soil nitrogen (N) (less than 10 mg·kg<jats:sup>−1</jats:sup> N) in the upper 15 cm. Rolled winter annual cover crops show promise for controlling annual weeds in organic no-tillage systems, but additional research is needed on methods to increase vegetable crop yields in rolled cover crops.</jats:p>

Legume cover crop management and organic amendments application: Effects on organic zucchini performance and weed competition

“…2b). This result is in accordance with Leavitt et al (2011), who suggested that cover crop mulches were associated with low levels of soil N (less than 10 mg N kg −1 ) in the upper 15 cm. Indeed, most of the indices of competition indicated that zucchini grown in RC systems was weaker than in GM and FA, suffering a reduction in crop N uptake and increase of weed competitive ability.…”

Cover Crop Effects on Light, Nitrogen, and Weeds in Organic Reduced Tillage

“…Although our work did not include a vegetable cash crop, previous work has been done with vegetables in no-till cover crop mulch with mixed results. Mulvaney et al (2011) found that collard production was unaffected by growing in mulch, but Leavitt et al (2011) found that cover crop mulch reduced tomato, pepper, and zucchini yields compared with no-mulch treatments. Drinkwater et al (2000) found that even with an excellent layer of mowed hairy vetch mulch, competing weeds can still exert severe pressure to reduce crop yields, and relying only on mulch may not be a sufficient form of weed management.…”

“…Regions requiring early spring planting of vegetable crops may not provide enough growing degree days to accumulate sufficient cover crop biomass and maturity for timely and effective termination before cash crop planting (Brennan et al 2009). Additionally, cover crops may reduce vegetable crop emergence and yield due to tie-up of soil N and reduced soil temperatures (Kumar et al 2009;Leavitt et al 2011) and may be ineffective at weed suppression (Carr et al 2011). Ryan et al (2011) found that more than 15 Mg ha −1 rye (Secale cereale) cover crop biomass is needed to completely suppress weeds, and Teasdale and Mohler (1993) found that suppression of weeds in mulch varies by weed species and mulch variety.…”

The influence of cover crop variety, termination timing and termination method on mulch, weed cover and soil nitrate in reduced-tillage organic systems

“…Compared with rye, higher weed populations have been observed in hairy vetch cover crops 20,36 , especially when flail-mowed 14 . Mixes of grains and legumes often can produce more biomass than either alone [37][38][39] , with plant tissue N concentrations between that of both constituents 37 , and can effectively reduce weeds 11,32,40 .…”