Conventional tillage and crop establishment methods for the rice–wheat (RW) system are input intensive (water, labour and energy). About 24.5 million tonnes of rice residues are burnt every year on farms in north-western India before sowing of wheat, causing air pollution and soil health degradation. Therefore, alternative tillage, crop establishment and residue management practices are needed for long-term sustainability of the RW system. A 4-year field study evaluated four tillage and crop establishment methods in rice (in main plots) and three tillage and rice residue management methods in wheat (in subplots) for their effects on yield, soil fertility, and profitability of the RW system. Average rice yields were similar under conventional puddled transplanted rice (PTR) and conventional till dry seeder rice (CTDSR). Both of these treatments produced significantly greater yields (10–16%) compared with zero till DSR (ZTDSR) and ZT machine transplanted rice in non-puddled soil, respectively, regardless of tillage and straw management methods in the previous wheat crop. Wheat yields in ZT wheat (ZTW) with 100% surface retention of rice residue (+R) were significantly greater than conventional till without residue retention after 2 years of experimentation, and accompanied by significant increases in macro-nutrient (potassium) availability in soil. The ZTW−R (no residue) treatment produced 15% lower wheat yield than ZTW+R. System yield was highest in CTDSR-ZTW+R, which was 5% higher than the conventional practice PTR-CTW−R, resulting in Rs 17 000 ha⁻¹ greater net returns.

Context. Understanding ecology in grass–legume pastures can help support strategies aimed at maintaining canopy stability in terms of botanical composition.

Aims. This 2-year study evaluated spatial variability, focusing on plant structural characteristics in a Marandu palisadegrass [Urochloa brizantha (Hochst. Ex A. Rich.) R.D. Webster cv. Marandu]–forage peanut (Arachis pintoi Krapov. and W.C. Greg. cv. BRS Mandobi) mixed canopy under grazing in continuous stocking management.

Methods. The pasture was managed with canopy height of 20–25 cm. The experimental area had a permanent sample grid containing 50 pre-established and georeferenced plots. Principal component analysis was performed, and spatial dependence structure of the first principal component and structural variables were separately characterised by geostatistical analysis.

Key results. There was spatial dependence of the structural characteristics, with marked spatial heterogeneity in the distribution of all variables. Taller grass canopies caused competition for light between species, reducing legume contribution and inducing more erect forage peanut growth habit. Conversely, in areas with lower grass canopy height, forage peanut botanical composition increased to up to 70%, as it propagated more effectively by stoloniferous propagation.

Conclusions. The canopy structure spatial variability of a Marandu palisadegrass–forage peanut mixed pasture determines the overall average pasture grass/legume proportion. In regions with taller canopies, Marandu palisadegrass was favoured, while in areas with shorter canopy, forage peanut proportion was promoted. Satisfactory legume proportions can be reached in the canopy despite areas with reduced legume contribution.

Implications. Our findings using geostatistical techniques facilitate the development of useful and innovative tools allowing better comprehension for the management of mixed pastures.

Context. Tagasaste (Cytisus proliferus) has potential to supplement pasture production in steep-hill country and increase pasture resilience.

Aims. To (1) quantify production of edible dry matter (EDM) of pruned 2-year-old tagasaste shrubs and branches from unpruned 10-year-old tagasaste trees, and (2) determine the effect of proximity of the 10-year-old tagasaste trees on selected pasture species established as spaced transplants.

Methods. A site was established on the eastern coast of the North Island of New Zealand on steep-hill country (>20° slope). Tagasaste and pasture species production was measured over 3 years.

Results. Tagasaste shrubs produced an average of 2.7 kg EDM shrub⁻¹ year⁻¹ and a tree branch produced 129 g EDM year⁻¹. The metabolisable energy content of tagasaste branches averaged 10.0 MJ kg EDM⁻¹, the crude protein content ranged from 18% to 27% and neutral detergent fibre content averaged 39%. Branch diameter and length were poor predictors of EDM branch⁻¹. There was no effect of increasing proximity to tagasaste on DM production of the resident pasture. Effects of increasing proximity to tagasaste on the growth and survival of selected pasture species are reported in a companion paper.

Conclusions. Edible-DM production was much greater from shrubs than tree branches and it was not possible to predict branch EDM from branch diameter or length.

Implications. A tagasaste silvopasture is likely to be more productive if tagasaste is managed for grazing in situ than if using mature trees for harvesting of branches for browse.

Context. Phytic acid is the major storage form of phosphorus in cereals and is considered an anti-nutritional factor because it chelates major mineral micronutrient cations, resulting in micronutrient malnutrition in humans. For monogastric animals fed maize (Zea mays L.) grains, the stored phosphorus does not release into the digestive tract, leading to phosphorus deficiency and environmental pollution.

Aims. The aim of the study was to develop maize lines with a lower level of phytic acid that might substantially enhance the nutritional value of maize.

Methods. The lpa1 mutant allele conferring low phytic acid was transferred into the parental lines of popular maize hybrid DMH 121 (i.e. BML 6 and BML 45) through marker-assisted backcross breeding. Foreground selection was performed using a co-dominant single nucleotide polymorphism marker through a high-resolution melting approach, and background selection was undertaken using 50–55 polymorphic sequence-tagged microsatellite site markers.

Key results. Near-isogeneic lines were produced with >90% recurrent parental genome and reduction of phytic acid content by up to 44–56% compared with the original lines.

Conclusions. The near-isogeneic lines carrying lpa1 can be used to reconstitute DHM 121 with low phytate content.

Implications. The low-phytate maize hybrids produced can be useful in reducing micronutrient malnutrition in humans, as well as environmental pollution.

Context. Rock phosphate reserves are decreasing, and requirements to mitigate environmental impacts of farming soils with excess phosphorus (P) are increasing.

Aims. White clover is an allotetraploid hybrid between Trifolium pallescens and T. occidentale. Understanding the P response characteristics of these progenitor species will allow selection of germplasm for development of synthetic white clovers with improved phosphorus-use efficiency (PUE).

Methods. Shoot and root weights and P nutrition characteristics were compared for three Trifolium pallescens, six T. occidentale accessions, and a white clover cultivar in a glasshouse experiment using a low P soil amended with five rates of P.

Key results. White clover had the highest and most P responsive shoot and root dry weights (DW), and T. pallescens was least responsive to P. In the highest P treatment, T. pallescens had the highest shoot and root %P and the lowest shoot DW:total plant P ratio. There was significant variation among progenitor accessions. Spanish accessions of T. occidentale had comparable shoot DW to white clover and higher PUE. Traits of T. pallescens indicated strong adaptation to low P but low productivity, while traits of T. occidentale were more aligned with the white clover cultivar.

Conclusions. The substantial variation in P nutrition characteristics within the progenitor species of white clover could be exploited in breeding programs.

Implications. Comparing the P responses of a wider range of progenitor accessions could inform breeding to improve white clover’s low soil P tolerance through development of synthetic white clovers.

Climate change and global warming are leading to severe drought stress, causing damage to crops in different regions of the world. Drought stress is an abiotic stress that interferes with major metabolic pathways, influencing mainly morphological, physiological and biochemical parameters of plants, ultimately resulting in decreased growth and yield of crops. Plants should be able to utilise available moisture efficiently, and there is a need to focus on organic and eco-friendly methods for improving crops facing drought stress. A practical approach for enhancing growth and development under stressful conditions is the application of plant growth promoting rhizobacteria (PGPR), soil microbes that help plants to cope with extreme ecological conditions. This review aims to highlight the function of various PGPR metabolites that help to mitigate water-deficit conditions. These microbes exist naturally in the rhizosphere of plants, and they enhance plant growth by several direct mechanisms such as aminocyclopropane-1-carboxylate deaminase and osmolyte production, secretion of exopolysaccharides and phytohormones, triggering of antioxidant defence mechanisms against reactive oxygen species and production of volatile organic compounds, as well as by indirect mechanisms including enhancing induced systemic resistance and pathogen suppression. This review recommends the use of PGPR for improving growth and development of crops under drought stress and supports their role as effective and sustainable bioinoculants for enhancing the growth and production of crops.

Context. Barley grass (Hordeum spp. L.) is an annual, invasive grass weed of southern Australian crops and pastures, frequently associated with weight loss and carcass damage in sheep due to its sharp seeds. Knowledge gaps exist regarding optimal density thresholds for effective control to reduce impacts on animal production. The value of integrated weed management (IWM) over individual control options for reducing barley grass populations in pasture is also unknown.

Aims. We aimed to develop a model for simulating the population dynamics of barley grass within lucerne (Medicago sativa L.) pastures of southern Australia and to test the hypothesis that combining herbicides with mowing will be more effective for removing barley grass seedbanks over time than individual control measures.

Methods. The model was developed within Microsoft Excel and adapted from other annual grass models. The model takes a Monte Carlo approach to simulate control impacts on weed seedbanks over 10 years using five weed-control density thresholds. It was parameterised using data from recent experiments and available literature.

Key results. The most effective long-term control strategy for barley grass occurred with a density threshold of 5 seedlings m⁻² by combining early and late herbicide applications, and by combining early and late herbicides with mowing, reducing the seedbank by 86% and 89%, respectively.

Conclusions. Simulation results showed that IWM programs were more effective than individual control options in reducing the barley grass seedbanks over 10 years, particularly at low weed densities (≤50 seedlings m⁻²).

Implications. Incorporation of this model into a bioeconomic grazing systems model will be valuable for determining the economic impacts and optimal weed-control strategies for minimising the effects of barley grass seed contamination in lamb production systems.

Context. Herbicide-resistant annual ryegrass (Lolium rigidum; ARG) is a major weed of commercial significance globally, including no-till wheat-based production systems in south-eastern Australia.

Aims. To compare the cost-effectiveness of different crop sequences and intensities of weed management to control ARG in rainfed grain production.

Methods. Two on-farm studies in southern New South Wales, Australia, compared the effect of combinations of 3-year crop-sequence options (continuous wheat, 1- or 2-years of break crops), conservative or aggressive weed-control measures, hay cuts, legume brown manure (BM), and/or weed-free winter fallow on in-crop ARG infestations and soil seedbanks. Gross margins were calculated for each combination of treatments to compare system economic performance.

Key results. Double-breaks consisting of two consecutive broadleaf crops, or canola–cereal hay, were frequently the most profitable and effective ARG control strategies. Single canola or lupin crops, BM, cereal hay, and fallow all significantly reduced subsequent in-crop ARG and seedbank numbers compared with continuous wheat. Aggressive in-crop control measures in wheat were more expensive than those applied to break crops. Gains in ARG control could be lost by a single year of poor weed control.

Conclusions. High levels of control (>95%) over three consecutive seasons are required to reduce ARG seedbanks, and this is most cost-effectively achieved with diverse crop sequences.

Implications. Farmers with high populations of ARG can reduce seedbanks by growing three crops sequentially that achieve complete weed seed control. This must be followed with ongoing high levels of control in subsequent years to keep ARG seedbanks low.