Experiments were conducted to investigate the effect of Lolium rigidum (annual ryegrass) seed developmental stage and application rate of glyphosate and SpraySeed (paraquat 135 g/L + diquat 115 g/L) on the number, germinability, and fitness of seeds produced. Glyphosate (450 g/L) was most effective when applied at a rate of 0.5–1 L/ha during heading and anthesis, reducing the number of filled seeds produced compared with unsprayed plants. Application post-anthesis, when seeds were at the milk to soft dough stage, was less effective. SpraySeed was most effective when applied post-anthesis, during the milk and early dough stages of seed development at a rate of 0.5–1 L/ha, resulting in the production of few viable seeds. Although some filled seeds were produced, most of the seeds were dead. Application during anthesis or once the seeds reached soft dough stage was less effective. For both herbicides, those seeds that were capable of germinating were smaller and had slower radicle and coleoptile growth, resulting in slower early seedling growth and reduced biomass production within the first month of growth. Additionally, glyphosate application reduced the proportion of seeds exhibiting dormancy. The anticipated reduction in seed competitive ability and altered emergence timing resulting from late-season herbicide application, even when application timing is not optimal, could be exploited to reduce the likelihood of successful L. rigidum establishment in the following season.

Conventional farming practices can lead to soil degradation and a decline in productivity. Regenerative agriculture (RA) is purported by advocates as a solution to these issues that focuses on soil health and carbon sequestration. The fundamental principles of RA are to keep the soil covered, minimise soil disturbance, preserve living roots in the soil year round, increase species diversity, integrate livestock, and limit or eliminate the use of synthetic compounds (such as herbicides and fertilisers). The overall objectives are to rejuvenate the soil and land and provide environmental, economic, and social benefits to the wider community. Despite the purported benefits of RA, a vast majority of growers are reluctant to adopt these practices due to a lack of empirical evidence on the claimed benefits and profitability. We examined the reported benefits and mechanisms associated with RA against available scientific data. The literature suggests that agricultural practices such as minimum tillage, residue retention, and cover cropping can improve soil carbon, crop yield, and soil health in certain climatic zones and soil types. Excessive use of synthetic chemicals can lead to biodiversity loss and ecosystem degradation. Combining livestock with cropping and agroforestry in the same landscape can increase soil carbon and provide several co-benefits. However, the benefits of RA practices can vary among different agroecosystems and may not necessarily be applicable across multiple agroecological regions. Our recommendation is to implement rigorous long-term farming system trials to compare conventional and RA practices in order to build knowledge on the benefits and mechanisms associated with RA on regional scales. This will provide growers and policy-makers with an evidence base from which to make informed decisions about adopting RA practices to realise their social and economic benefits and achieve resilience against climate change.

Field experiments were sown with alfalfa mosaic virus (AMV)-infected or healthy seed of burr medic (Medicago polymorpha) and grazed by sheep. Seed-infected plants acted as primary sources for virus spread by naturally occurring aphids. Admixture with annual ryegrass (Lolium rigidum), a non-host of AMV, and different insecticides were used in attempts to suppress virus spread. Sowing swards to provide the ratios 1:4 and 1:13 of medic:ryegrass plants diminished AMV spread in medic plants by 23% and 45% respectively. Applications of organophosphorus (demeton-s-methyl), carbamate (pirimicarb) and newer generation synthetic pyrethroid (alpha-cypermethrin) insecticides, all significantly decreased final AMV incidence. Alpha-cypermethrin was the most effective, suppressing AMV incidence by 87% (two sprays), 79% (one late spray) and 65% (one early spray). Two sprays of demeton-s-methyl decreased incidence by only 36%, while two and 2 weekly applications of pirimicarb diminished it by 29-65% and 35-70% respectively. AMV infection of medic seed harvested decreased by up to 76% in sprayed plots. Insecticide treatment did not prevent winged aphids from landing but numbers of wingless Acyrthosiphon kondoi colonising swards were suppressed by up to 92% by spraying with pirimicarb and up to 96% by alphacypermethrin. A. kondoi were much slower to recover with alpha-cypermethrin than with pirimicarb, the former still significantly diminishing its numbers 35 days after spraying. Alpha-cypermethrin was also very effective at suppressing Halotydeus destructor and Penthaleus major but not Sminthurus viridis. Greater effectiveness of insecticides in controlling spread of AMV in pasture than has been found previously with non-persistently aphid-transmitted viruses in annual crops seems due to the key role played by wingless aphids as virus vectors.

No abstract

In southern Australia, intercropping, pasture cropping and overcropping have evolved as techniques to address environmental problems such as dryland salinity and wind erosion and to utilise soil water outside the conventional winter-dominant growing season. We paired three winter-dormant pastures, including two subtropical C4 perennial species (Rhodes grass, Chloris gayana; Gatton panic, Megathyrsus maximus) and the summer-active perennial C3 legume siratro (Macroptilium atropurpureum), with a conventional barley (Hordeum vulgare)–lupin (Lupinus angustifolius) rotation to explore the extent to which different summer-active species reduced crop yields. We also examined whether the competition for resources could be altered by supplying increased nitrogen to the crop and changing the row spacing of the pasture. Under high-input conditions, pasture reduced cereal crop yields by up to 26% and lupin yields by up to 29%. Under low-input conditions, pasture cropping did not significantly reduce crop yield, and frequently increased crop yields. With low inputs, barley yield increases in 2011 ranged from 23% to 31%. In lupins under low-input conditions, yield increases ranged from 91% to 106% in 2010 and from –6% to +39% in 2012. The impact of the crop on the pasture was less pronounced, where the timing of pasture growth was delayed by the crop, but absolute levels of production were not influenced by the crop. Row spacing altered the temporal dynamic of pasture production; initially, the pasture produced less than the narrow spaced equivalent, but after 2 years, production exceeded that in the narrow row. Across all pasture species in 2009 and 2012, winter pasture production reduced crop yield by 0.32 and 0.4 t grain/ha pasture biomass produced, implying that moderate yield losses occurred because pasture production was also moderate. In the other two years, winter pasture production did not affect crop yield, suggesting that the pasture was able to utilise resources surplus to crop requirements. In this environment, with this combination of crops and summer-active pastures, higher levels of inputs did not enhance crop yield in a pasture-cropping system. We suggest that grain yield losses are lower in the low-input system and this implies that, at some level, competition between the species was reduced in a nitrogen-limited environment and the extent of the competition depended on season.