In‐Season and Carry‐Over Effects of Cover Crops on Productivity and Weed Suppression

Abstract

Data necessary to evaluate cover crop multifunctionality are lacking, particularly for cool, short‐season cropping niches typical of northern New England. We quantified cover crop biomass, weed suppression, and carry‐over effects on subsequent crop and weed growth in 12 winter cover crop treatments {monocrops and mixtures of annual ryegrass [Lolium multiflorum Lam.], winter rye [Secale cereale L.], alfalfa [Medicago sativa L.], crimson clover [Trifolium incarnatum L.], white clover [T. repens L.], hairy vetch [Vicia villosa Roth], soybean [Glycine max (L.) Merr.], and forage radish [Raphanus sativus L.], and a weedy fallow [control] treatment}. The forage radish treatments (11 and 28 kg ha−1 seeding rates) were among the highest producers of fall cover crop biomass in all 4 site‐years. The forage radish treatments were also among the most weed‐suppressive in the fall, reducing weed biomass relative to the weedy fallow treatment by 89 to 97% in each of the 4 site‐years. In the spring, annual ryegrass was among the highest (ranging from 349–571 g m−2 across site‐years) and alfalfa was among the lowest (39–287 g m−2) biomass‐producing treatments in 3 out of 4 site‐years. Weed biomass in the spring was 73 to 99% lower in annual ryegrass, hairy vetch, and hairy vetch–winter rye mixture treatments than in the weedy fallow treatment. Biomass of the sorghum [Sorghum bicolor (L.) Moench]–sudangrass [S. sudanense (Piper) Stapf] phytometer was higher following white clover, hairy vetch, the hairy vetch–rye mixture, and both forage radish treatments compared to following annual ryegrass.Core Ideas Cover crops differ in their ability to provide multiple ecosystem services. This study quantified weed suppression services in 12 cover crop treatments. Weed suppression in fall, spring, and a subsequent phytometer differed among the treatments. Phytometer biomass was higher following forage radish and several legume cover crops compared to annual ryegrass. Cover crop multi‐functionality and tradeoffs were assessed with spider plots.

Do cover crop sowing date and fertilization affect field weed suppression?

“…It was found a linear relationship between weed and cover crop biomass in 2015 (Table 4). In the following year, no significant correlation was calculated at 7 WAH and 12 WAH without fertilization, which is in line with the results of Hodgdon et al (2016). Further, it was observed a linear relationship between weed biomass and density in 2016 (R 2 = 0.4406, P ≤ 0.05), however this relationship was much weaker and not significant in 2015 (R 2 = 0.2522).…”

“…In other studies, cover crops inhibited weed biomass by more than 80%, due to competitive and biochemical effects (Lawley et al 2011, Silva 2014, Rueda-Ayala et al 2015. A significant reduction of weed biomass of up to 97% was observed by radish cover crops in fall in different studies (Stivers-Young 1998, Hodgdon et al 2016. Kruidhof et al (2008) measured similar weed biomass reductions of 80% and 86% at 7 and 12 weeks after sowing.…”

Winter cover crops influence weed establishment and nitrogen supply to maize

“…The low weed population with BO can be due in part to the quick and lasting SC in addition to hindering weed growth from the BO on some weed species (Flower et al 2012, Price et al 2006. Previous studies found similar results with the use of CC preventing or reducing weed infestation (Florentin et al 2011, Hodgdon et al 2016. This becomes particularly important in modern agricultural systems worldwide given the current herbicideresistance problems worldwide (Kaundun et al 2014).…”

“…However, the use of mixture of cover crops was a useful strategy to improve these parameters and as reported in previous studies (Finney et al 2016), all the CC treatments provided some improvement for SC and suppression of weeds while bare soil during the winter provided an open window for weed infestation. Eradication of these weeds can be costly and is becoming increasingly difficult (Hodgdon et al 2016, Kaudun et al 2014, thus, it is important to highlight the great ecosystem service that increasing soil cover and decreasing weed infestation by using the right combination of cover crops could represent for farmers in the short and especially in the long term. The winter fallow treatment generated low biomass production (from weed infestation) (Table 3).…”

“…Optimum nitrogen (N) supply and proper weed control is often considered the main challenges for maize production, especially under NT system (Bender et al 2013, Lundy et al 2015. Nitrogen immobilization can be higher under NT system due to the presence of high amounts of plant residues on the soil surface (Frasier et al 2016), and weed control typically relies on chemical control (Hodgdon et al 2016, Kaundun et al 2014. Legume CC can provide N for the succeeding crop (Florentin et al 2011, Mahama et al 2016, with the potential of replacing part of the fertilizer N application (Fontoura and Bayer 2009, Mahama et al 2016, Tully et al 2015.…”