Abstract
Weeds are an increasingly significant issue inhibiting agricultural production worldwide. Forage conservation could form part of an integrated weed management program if ensiling killed weed seeds. In Experiment 1, seeds of five grass (Hordeum spp., Bromus diandrus, Bromus hordeaceum, Lolium rigidum and Vulpia spp.) and two broad-leaved temperate weed species (Echium spp. and Raphanus raphanistrum), that were either untreated, ensiled in pasture (Trifolium subterranean/Lolium rigidum mixture) forage for a minimum of three months, underwent 48 h in sacco digestion in steers or ensiled prior to digestion were tested for germinability and viability. In Experiment 2, seeds of eight tropical weed species (Cenchrus ciliaris, Rumex spp., Bidens pilosa, Sorghum halepense, Urochloa panicaoides, Paspalum dilatatum, Brachiara eruciformis and Choris truncata) were ensiled in Sorghum bicolor forage. In Experiment 3, L. rigidum and R. raphanistrum seeds were ensiled in either Medicago sativa forage wilted to 336.9, 506.5 or 610.7 g/kg dry matter; or in chaff to which water or water plus acid was added at rates to achieve 350, 450 or 550 g/kg dry matter content with lactic plus acetic acid added in the ratio of 3:2 at 80, 45 or 10 g/kg DM, respectively. In Experiment 4, L. rigidum and R. raphanistrum seeds were ensiled in cotton wool to which water or water plus acid was added at the same rates as in Experiment 3. Germinability of all seeds following ensiling was substantially reduced or nil. The extent of the reduction varied with species and experiment. In sacco digestion reduced germinability in Experiment 1, but to a lesser extent than ensiling; while ensiling plus digestion reduced germination rates to 0%.
Highlights
Weeds are a major constraint to agricultural production in both developed and developing countries [1]
The germinability of seeds treated with E was lower (p < 0.05) for Hordeum spp., L. rigidum and Echium spp. but higher (p < 0.05) for A. fatua compared to D
Increasing forage dry matter (DM) content did not reduce the impact of ensiling on seed viability of winter growing weed species, based on the artificial silage results obtained in Experiments 3 and 4
Summary
Weeds are a major constraint to agricultural production in both developed and developing countries [1]. The management of agricultural crop and pasture weeds in developed countries has relied extensively on the use of herbicides since their rapid development after World War II. More recently the adoption of conservation agriculture with the aim of achieving sustainability has reduced the use of tillage as a management practice for soil preparation and weed control prior to sowing of crops and pastures. This has increased reliance on herbicide usage for weed control which has increased selection pressure and the development of herbicide resistance [3,4]. Future weed management will require alternative strategies that do not include tillage while reducing reliance on herbicides
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