Context. Red leather leaf (RLL), caused by Neospermospora avenae, is a common foliar disease of oats in south-eastern Australia but its impact on hay and grain yield and quality is unknown.

Aim. We aimed to determine the effect of RLL on grain yield and quality of commercial milling oat varieties, and biomass and nutrition of hay oat varieties, with a range of host plant resistance responses by comparing fungicide and disease treatments.

Methods. A total of eight field experiments were conducted in 2019 and 2020; four experiments each investigated the effects of RLL on hay or milling oats. In each experiment, six or seven oat varieties were sown with a disease or fungicide imposed. RLL severity was estimated visually for each experiment. Biomass yield and quality traits at early milk development stage were measured for hay oat experiments; and grain yield and quality for the milling oat experiments.

Key results. RLL severity (% leaf area affected: 0–44% in hay oats and 2–61% in milling oats) varied with the season, varietal resistance, and treatments. RLL caused significant losses in most experiments, with reductions in biomass of up to 3.5 t/ha (22%) in hay oats and grain yield of up to 1.1 t/ha (21%) in milling oats.

Conclusions. RLL can be a severe foliar disease of oats in south-eastern Australia and cause significant losses in both hay and milling oat crops.

Implications. Growing varieties with resistance can effectively reduce potential loss due to RLL and growers are required to adapt fungicide strategies reflecting seasonal conditions and product type (grain or hay).

Context Using forage grass species with complementary growth and resource-use strategies to enhance forage plant diversity in pastures may be an alternative to traditional monocultures in tropical regions.

Aims This study aimed to determine whether a mixture of three perennial tropical forage grasses (Andropogon gayanus cv. Planaltina, Panicum maximum cv. Massai, and Brachiaria brizantha cv. BRS Piatã) could be an alternative to enhance herbage intake rates relative to their respective monocultures.

Methods The treatments corresponded to three perennial tropical forage grasses cultivated as monocultures and as a mixture composed of all three species. Defoliation management corresponded to a pre-cutting height of 35 cm and post-cutting height of 17.5 cm.

Key results The botanical composition of the mixture was dynamic throughout the experimental period, with variations in the proportion of species across seasons. The upper half of the canopy predominantly comprised leaves for all treatments. The canopy structure of the mixture allowed for greater herbage intake rates than monocultures during winter/early spring. Andropogon gambagrass showed lower herbage intake rates than the other treatments.

Conclusions The findings of this study indicate that it is possible to combine tropical forage grass species without compromising canopy structure and grazing animal responses, compared with single-species grass pastures.

Implications The selection of forage species for mixed pastures should consider their phenological cycle, growth, and resource-use strategies to achieve temporal complementarity and provide an optimal grazing environment for animals throughout the year.

Context Brazilian livestock contributes significantly to pasture-based global animal protein production, but faces economic and environmental challenges due to unsustainable practices. Silvopastoral systems (SPS) offer a promising solution to these issues.

Aims This study aims to assess the impact of Tithonia diversifolia in a SPS with Urochloa brizantha cv. Xaraés (Xaraés grass) compared to traditional exclusive pasture (EP).

Methods The experiment was conducted using a completely randomized design with eight paddocks (four EP and four SPS with T. diversifolia), grazed by Santa Ines male lambs across six stocking cycles. Herbage biomass production, morphological composition, and nutritive value, animal stocking rate, and proportion of T. diversifolia intake using δ¹³C were evaluated.

Key results Xaraés grass biomass production was unaffected by the presence of T. diversifolia in SPS. SPS with T. diversifolia accumulated more total herbage biomass and greater nutritive content than EP. However, Xaraés grass in SPS showed a reduction in leaf fraction and increase in stem and fibrous fractions. T. diversifolia constituted 42.7% of the biomass in SPS, while only 13.74% of fecal carbon originated from it.

Conclusions SPS with T. diversifolia produces a greater total herbage biomass than EP, but negatively affects leaf fraction and nutritive value of Xaraés grass. Lambs showed a preference and selective intake for Xaraés grass over T. diversifolia.

Implications Integrating T. diversifolia in SPS can increase herbage biomass, but careful management is necessary to preserve nutritional quality and minimize lamb selectivity.

Context There is no consensus between farmers and researchers about timing for ryegrass desiccation before corn sowing, considering interactions between ryegrass straw, nitrogen immobilization, and allelochemical release impacting corn growth.

Aims This study aims to assess the effects of different desiccation timings of annual ryegrass (Lolium multiflorum Lam.) and nitrogen management on corn. We sought to elucidate whether corn growth inhibition is attributable to allelochemical release or nitrogen immobilization.

Methods A two-year field factorial experiment was conducted, with Factor A comprising fallow and three ryegrass desiccation timings before corn sowing, and Factor B involving two nitrogen fertilization methods to evaluate N immobilization. Laboratory experiments assessed allelopathic properties using a 3 (desiccation periods) × 5 (ryegrass extract concentrations) factorial design. Assessments included corn (Zea mays) germination, seedling radicle and coleoptile length, and germination speed.

Results Ryegrass desiccation timing of less than 20 days before corn sowing reduced corn stature at the beginning of development and grain yield, due to nitrogen immobilization and allelopathic influences possibly exercised by caffeic acid and epicatechin present in roots and shoots, released as residues decomposed. Non-desiccated ryegrass aqueous extracts reduced germination speed and germinability. Root/shoot extracts reduced seedling elongation. Desiccated aqueous extracts at 15 and 30 days before corn sowing didn’t present inhibitory effects.

Conclusion Nitrogen enhances corn growth regardless of ryegrass influence, under these experimental conditions. Ryegrass desiccation timing affects corn yield; and delaying corn sowing post-desiccation mitigates losses. Ryegrass extracts inhibit corn germination and viability, regardless of concentration, possibly due to phytotoxic compounds.

Context Long-term negative potassium (K) balances in crop production have depleted soil K levels in Western Australia (WA). Previous research has focussed on sand-textured soils, but recently, monitoring of crops grown on loam-textured soils has shown deficient or marginal shoot K concentrations where Colwell K 0–10 cm is above current critical levels.

Aims The aims were to examine whether grain yield responses to fertiliser K can be detected on loam-textured soils and if soil test calibration curves can be identified for these soils.

Methods Eight field trials were conducted with wheat on loam-textured soils. The same experimental design was used at all sites; six levels of K applied at sowing, from 0 to 200 kg K ha⁻¹ with one treatment including a split application. Soil and plant test calibration curves were modelled using measurements from the trials.

Key results Grain yield responses of 0.69 to 1.37 t ha⁻¹ to fertiliser K (P < 0.05) occurred in 4 of 8 trials. Relative yield was closely related to soil exchangeable K and the goodness of fit of the soil test calibration curves increased as the depth of sampling increased. The best soil test calibration curve was for sampling 0–40 cm.

Conclusions This research confirms that on some loam-textured soils, yield loss is occurring to K deficiency if no K fertiliser is applied.

Implications As soil K reserves are run down, soil sampling at 0–40 cm on loam-textured soils will provide the most accurate monitoring of soil K deficiency for wheat production.