Growing vetches (Vicia villosa Roth) in irrigated cotton systems: inputs of fixed N, N fertiliser savings and cotton productivity

Abstract

We compared symbiotic N 2 fixation by winter forage legumes (clovers, medics and vetches) using the 15 N natural abundance technique in three experiments. Vetches (Vicia spp.) were the most productive legumes, and woollypod vetch fixed (shoot+root) up to 265 kg N ha )1 (mean 227 kg N ha )1 ) during a 4-5 months period over winter and early spring. Balansa and Berseem clovers, and Gama medic were highly productive in the first experiment, but fixed significantly less N than woollypod vetch in the second experiment.A 6-year study (1997)(1998)(1999)(2000)(2001)(2002)(2003) compared cotton (Gossypium hirsutum L.) systems with and without vetch, or with faba beans (Vicia faba L.) to assess the effects of these crops on cotton production. Woollypod vetch was grown either between annual cotton crops, or between wheat (Triticum aestivum L.) and cotton crops. Vetch added 230 kg N ha )1 (174 kg fixed N ha )1 ) to the soil when incorporated as a green manure. Faba bean shoot residues and nodulated roots contributed 108 kg fixed N ha )1 to the soil, following the removal of 80 kg N ha )1 in the harvested seed (meaned over three crops). Lablab (Lablab purpureus L. -summer-growing and irrigated) added 277 kg N ha )1 (244 kg fixed N ha )1 ) before incorporation as a green manure in the first year of the experiment.The economic optimum N fertiliser rate for each cropping system was determined every second year when all systems were sown to cotton. Cotton following cotton required 105 kg fertiliser N ha )l , but only 40 kg N ha )l when vetch was grown between each cotton crop. Cotton following wheat required 83 kg fertiliser N ha )l but no N fertiliser was needed when vetch was grown after wheat (the highest yielding system). Cotton following faba beans also required no N fertiliser. The vetch-based systems became more N fertile over the course of the experiment and produced greater lint yields than the comparative non-legume systems, and required less N fertiliser. While no cash flow was derived from growing vetch, economic benefits accrued from enhanced cotton yields, reduced N fertiliser requirements and improved soil fertility. These findings help explain the rotational benefits of vetches observed in other regions of the world.

Effect of 15n-labeled hairy vetch and nitrogen fertilization on maize nutrition and yield under no-tillage¹

“…On average, 184 kg ha -1 yr -1 N was accumulated in the hairy vetch aboveground biomass, of which around 130 kg ha -1 N was biologically fixed from the atmosphere (Table 1). Rochester & Peoples (2005) found higher BNF in hairy vetch than in this study, contributing to 90 % of the total N in the biomass. Giller & Wilson (1993) and Seo et al (2006) reported hairy vetch N accumulation and biomass production ranging from 100 to 200 kg ha -1 N and from 2.5 to 5.0 Mg ha -1 , respectively, similar to the values found in the present study.…”

Remediation of degraded arable steppe soils in Moldova using vetch as green manure

“…Cahul aboveground 5.6 ± 0.2 2.2 ± 0.1 230 ± 12 184 ± 9 belowground 2.4 ± 0.2 0.9 ± 0.1 43 ± 4 34 ± 3 total 8.0 ± 0.4 3.1 ± 0.2 273 ± 16 218 ± 12 * Assuming a mean proportion of N 2 fixation on total N of 80 % according to Rochester et al (2005).…”

“…At both study sites, total N amounts of 254 and 273 kg ha −1 were incorporated in which 203 and 218 kg ha −1 (80 % of total N) were biologically fixed according to Rochester et al (2005). The incorporation of HVW as green manure showed a clear effect on the yields of the following main crops (Fig.…”

Crop Rotation Biomass and Effects on Sugarcane Yield in Brazil

“…[43], studying lupine in maize, and [44], studying velvet bean and sunn hemp in rice, could not find response to mineral N applied after green manure, and no N fertilizer was needed when vetch (Vicia spp.) was grown after wheat, and when cotton followed faba beans [42].…”