Grass–Legume Bicultures as Winter Annual Cover Crops

Abstract

Grass‐legume bicultures as winter annual cover crops may combine the N scavenging ability of grasses and the biological N2 fixation capacity of legumes to improve N management in crop production systems of the southeastern USA. A 3‐yr field experiment was conducted on a Norfolk loamy sand (fine‐loamy, kaolinitic, thermic Typic Kandiudults). The focus of this research was to examine the differences among legume monocultures and grass‐legume bicultures with regard to early spring dry matter (DM) and N accumulation, and related effects on soil inorganic N levels and subsequent corn (Zea mays L.) yield. Austrian winter pea [Pisum sativum L. subsp, sativum var. arvense (L.) Poir.], crimson clover (Trifolium incarnatum L.), commonve tch (Vicla saava L.), and hairy vetch (Vicla villosa Roth) were grown in monoculture and in bicultures with rye (Secale cereale L.), oat (Arena satira L.), and wheat (Triacum aestivum L.). Aboveground plant material was harvested in early March, late March, and mid‐April. Biomass was separated into component species and analyzed for total N and C concentrations. Averaged over 3 yr, legume component DM accumulation in monoculture and biculture ranged from 0.87 to 2.53 Mg ha−1, with a ranking of Austrian winter pea < hairy vetch < commonv etch < crimson clover. For the same period, the grass component DM accumulation ranged from 1.31 to 2.28 Mg ha−1, in the order rye = oat < wheat. Three‐year mean N accumulation values for the legume component followed the same relative ranking and ranged from 24 to 93 kg N ha−1. Grass factor N content ranged from 18 to 39 kg N ha−1 in the order rye < oat < wheat. For all bicultures, the average C:N ratio over the 3‐yr experiment was >30, suggesting that net N mineralization would occur from the decomposing cover crop residues. Profile soil inorganic N (0 to 90 cm) was greater in legume monoculture than in grass‐legume biculture treatments, indicating the ability of grasses to capture soil N. Corn yield was affected by the treatments in 1 of 3 yr, with greater yields following a legume monoculture than a grass‐legume biculture. Collectively, these results suggest that grass‐legume bicultures as winter annual cover crops have the potential to utilize residual soil NO3 and thereby minimize leaching while adding fixed N to cropping systems in the southeastern USA.

The ability of cover crops to reduce nitrogen and phosphorus losses from arable land in southern Scandinavia and Finland

“…Several studies have shown that undersown clover/grass mixtures with seed proportions of 10/90 by weight can reduce soil mineral N content and leaching to the same extent as a pure grass CC (Bergkvist et al 2011;Neumann et al 2011;. The use of legumes in pure stands as CCs for reduced N leaching has to date not been common practice in Scandinavia and Finland, since numerous studies have shown that their effectiveness in depletion of soil N is not reliable (Thorup-Kristensen 1994;Breland 1996a;Ranells and Wagger 1997;Känkänen et al 2003;Askegaard and Eriksen 2008;Möller and Reents 2009;Bergkvist et al 2011). Leguminous CCs that have been tested under Nordic climate conditions, undersown or sown after harvest, include the clovers (T. repens L., T. pratense L., and T. resupinatum L.) and also black medic (Medicago lupulina L.), hairy vetch (Vicia villosa L.), birdsfoot trefoil (Lotus corniculatus L.), and common vetch (Vicia sativa L.).…”

Green manuring effect of pure and mixed barley – hairy vetch winter cover crops on maize and processing tomato N nutrition

“…Adopting mixtures between legumes and non legumes can be an efficient tool to merge the advantages of the single species in the cover crop practice (Ranells and Wagger, 1997) achieving both environmental and agronomic benefits (Crews and Peoples, 2005). The use of mixtures leads to a radical modification of the biochemical composition of the aboveground biomass that will be incorporated into the soil , hence it could represent an important factor affecting the N mineralisation and the N availability for the subsequent crop.…”

N2 Fixation of Common and Hairy Vetches when Intercropped into Switchgrass

“…Similarly, common and hairy vetch are reportedly effective at increasing soil N and can fix N 2 required for a single biomass-cut system [12,13]. Specifically, common and hairy vetches have been reported to fix between 50 and 350 kg·N·ha −1 and 25 and 190 kg·N·ha −1 , respectively, in aboveground growth [14][15][16][17]. Common and hairy vetches are cool-season legumes, and as such, peak photosynthesis and subsequent fixation occur from winter until switchgrass' spring green-up.…”