Winter Forage Crop Harvest Time Impacts Regeneration of the Annual Weeds Barley Grass, Annual Ryegrass and Wild Radish

John W Piltz,Leslie A Weston,Stephen G Morris

doi:10.3390/agronomy11091700

Abstract

Barley grass (Hordeum spp.) is a short-lived annual weed which competes with preferred crop and pasture species and frequently contaminates wool and carcasses, and irritates the ears, eyes and noses of sheep. Barley grass, annual ryegrass (Lolium rigidum L.) and wild radish (Raphanus raphanistrum L.) are annual winter crop weeds which reduce grain yield through competition. In three consecutive years (2015 to 2017) cereal, legume and cereal/legume forage crops were grown and harvested in early October, late October or early November consistent with an early silage harvest (ES), late silage harvest (LS) or hay cut (H). A spring wheat cultivar was sown over each site in the following year (2016 to 2018). Weed density was recorded during the forage crop and wheat phases. Forage crop weed populations varied between years. Late paddock preparation for sowing in 2015 effectively eradicated barley grass from all forage crops; however, the competitiveness of legume and cereal/legume crops against annual ryegrass was reduced. In contrast, legume and cereal/legume mixtures tended to have higher barley grass densities than cereal crops in 2016 and 2017, when paddock preparation was earlier. Cutting in October 2015 reduced annual ryegrass and wild radish populations in 2016 wheat by 92.0% and 86.7%, respectively. In 2017 and 2018, regrowth and subsequent seed set following cutting appeared to negate cutting time effects for all crop and crop/legume combinations. Late paddock preparation, an early October forage harvest and effective regrowth control provided the best opportunity for barley grass, annual ryegrass and wild radish control in a single year.

Highlights

The traditional mixed farming areas of southern Australia are characterised by winter grain crops grown in rotation with a pasture phase with each phase between one and several years in length
Plant wheatanalysis crops included annual ryegrass, radish, clover species (Trifolium spp.), barley count was conducted in the R wild environment with particular use of the ASReml grass, annual medic species (Medicago spp.), wireweed
Our results show that weed control benefits occur from forage conservation as silage in contrast to hay

Summary

Introduction

The traditional mixed farming areas of southern Australia are characterised by winter grain crops grown in rotation with a pasture phase with each phase between one and several years in length. The two main annual grass species that commonly self-establish in southern Australian pastures are barley grass (Hordeum spp.) and annual ryegrass (Lolium rigidum L.), both of which are highly competitive crop weeds [3–6]. Annual ryegrass is a desirable pasture plant, producing substantial yields of high-quality grazing, but it is a major weed of broadacre winter crops [11]. Wild radish (Raphanus raphanistrum L.) is a major competitor in field crops [11], but of little importance in pastures where it is generally sporadic and eaten by livestock. These species were traditionally controlled by pasture and broadacre herbicides; the development of herbicide resistance, in annual ryegrass, has dramatically reduced herbicide efficacy [4,8,12–14]. There are populations of these species which cannot be controlled with commonly used herbicides [12,14,15], which has necessitated the investigation and use of alternative weed control strategies

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Conclusion