Context. In developing countries there is a preference to grow food crops rather than forage. However, suitable food–fodder based systems ensure year-round green fodder availability for profitable livestock production.

Aims. This study aimed to determine whether including single cut Egyptian clover (SEC) in the existing cropping systems could improve system productivity, forage availability and economic returns.

Method. Nine SEC based cropping systems were tested in a randomised complete block design with three replications.

Key results. Sorghum–SEC–wheat (late sown) cropping system produced 18% greater wheat equivalent yield compared with a popularly adopted sorghum–wheat system (8.9 Mg ha⁻¹). The water productivity (1.80 kg m⁻³) of this system was also improved in the sorghum–multi-cut Egyptian clover system (1.74 kg m⁻³). There was a marginal increase in dry matter yield and crude protein content of the succeeding sorghum crop when it was rotated with Egyptian clover. The inclusion of Egyptian clover also improved the soil organic carbon (23%) and available nitrogen (15%) compared with cereal–cereal systems. The findings identify a sustainable intensification option in the sorghum-based cropping system with short duration Egyptian clover (single cut) as an economically feasible and ecologically effective approach.

Conclusion. Integration of single cut Egyptian clover in sorghum–wheat rotation as a catch crop recorded greater system productivity, water-use efficiency and economic returns to achieve the sustainable crop intensification.

Implication. The SEC can be an effective option for diversification and intensification of cropping systems to improve fodder availability, yield, boost income and improve soil health.

Context. Production of rainfed (dryland) cotton (Gossypium hirsutum L.) occurs in many places globally, and is always burdened with greater uncertainties in outcomes than irrigated cotton. Assessing farm financial viability helps farmers to make clearer and more informed decisions with a fuller awareness of the potential risks to their business.

Aim. We aimed to highlight key points of uncertainty common in rainfed cotton production and quantify these variable conditions to facilitate clearer decision-making on sowing dates and row configurations.

Methods. The consequences of these decisions at six locations across two states in Australia, given estimates of plant-available water at sowing, are expressed in terms of comparable probability distributions of cotton lint yield (derived from crop modelling using historical weather data) and gross margin per hectare (derived from historical prices for inputs and cotton lint yield), using the copula approach. Examples of contrasting conditions and likely outcomes are summarised.

Key results. Sowing at the end of October with solid row configuration tended to provide the highest yield; however, single- and double-skip row configurations generally resulted in higher gross margins. Places associated with higher summer-dominant rainfall had greater chance of positive gross margins.

Conclusion. In order to maximise the probability of growing a profitable crop, farmers need to consider the variabilities and dependencies within and across price and yield before selecting the most appropriate agronomic decisions.

Implications. Given appropriate data on growing conditions and responses, our methodology can be applied in other locations around the world, and to other crops.

Context. Cannabis is a herbaceous annual plant that belongs to the Cannabaceae family, which is used in the production of fibre, paper, oil and pharmaceutical products.

Aims. The aim of this study was to identify drought-tolerant ecotypes and medicinal and industrial populations.

Methods. Due to the medicinal and industrial importance of cannabis, 12 cannabis ecotypes were collected from different regions of Iran. Then, their agronomic and phytochemical characteristics were evaluated under different soil moisture conditions.

Key results. The soil moisture levels had significant effects (P < 0.01) on the studied traits except for the 1000 seed weight. Based on duration of the growth period, the Tabas and Dasht-e-Moghan ecotypes were identified as early and late maturing ecotypes, respectively. Also, the highest stem dry weight and stem height/diameter ratio and the lowest seed yield were related to the Dasht-e-Moghan ecotype, which is valuable for fibre production. Based on seed yield (relative reduction) and some tolerance indexes, the Tabas and Tabrize ecotypes were shown to be the most tolerant and sensitive ecotypes, respectively. As soil moisture decreased, tetrahydrocannabinol levels increased and cannabidiol levels decreased. The highest amount of tetrahydrocannabinol was related to the Qom ecotype at 50% soil moisture and the highest amount of cannabidiol was related to the Rasht ecotype at 100% soil moisture.

Conclusions. Generally, these ecotypes had different responses to soil moisture. Some ecotypes were valuable in terms of the production of pharmaceutical metabolites and some in terms of fibre production.

Implications. Tolerant and sensitive ecotypes might be considered in production and also breeding programs.

Context. Tagasaste (Cytisus proliferus), a fast-growing leguminous tree, has potential to supplement pasture production in steep-hill country and to increase pasture resilience.

Aims. In the companion paper, we quantified tagasaste production characteristics. Here, we determine the effect of proximity of 10-year-old tagasaste trees on productivity of eight pasture species including grasses (perennial ryegrass, Lolium perenne; cocksfoot, Dactylis glomerata; prairie grass, Bromus willdenowii; microlaena, Microlaena stipoides), perennial legumes (white clover, Trifolium repens; red clover, T. pratense; lotus, Lotus pedunculatus), and an annual legume (subterranean clover, T. subterraneum).

Methods. A site was established in the East Coast region of the North Island of New Zealand on steep-hill country (>20° slope). Herbage production, nutritive value and survival of pasture species established as spaced transplants were measured over 3 years.

Results. Cocksfoot had high survival, herbage production and metabolisable energy content but was negatively affected by proximity to tagasaste. Microlaena was not significantly affected by proximity to tagasaste; however, it was much less productive and had lower nutritive values than the other grasses. Only 40% of perennial ryegrass transplants survived 3 years, and survival of perennial legumes was negligible. Subterranean clover was able to set seed in the open and in shade.

Conclusions. Cocksfoot was the most productive grass species, and microlaena was least affected by proximity to tagasaste. Given the poor persistence of perennial clovers, annual clovers may be better suited to a tagasaste silvopasture on steep, dry hillsides.

Implications. Mixtures of cocksfoot and subterranean clover may be well suited to summer-dry hillsides, between and under trees in a tagasaste silvopasture. Microlaena may provide some forage and can maintain groundcover despite shade.

Context. Perennial crop variety selection trials are often conducted over several seasons or years. These field trials often exhibit spatial correlation between plots. When data from multiple assessment times are analysed, it is necessary to account for both spatial and temporal correlation. A current approach is to use linear mixed models with separable spatial and temporal residual covariance structures. A limitation of these separable models is that they assume the same spatial correlation structure for each assessment time, which may not hold in practice.

Aims. This study aims to provide more flexible methods for modelling the spatio-temporal correlation in multi-assessment perennial crop data, allowing for differing spatial parameters for each time, together with modelling genetic effects over time.

Methods. The paper investigates the suitability of two-directional invariant multivariate autoregressive (2DIMVAR1) models for analysis of multi-assessment perennial crop data. The analysis method is applied to persistence data from a pasture breeding trial.

Key results. The multivariate autoregressive spatio-temporal residual models are a significant improvement on separable residual models under different genetic models. The paper demonstrates how to fit the models in practice using the software ASReml-R.

Conclusions. A flexible modelling approach for multi-assessment perennial crop data is presented, allowing differing spatial correlation parameters for each time. The models allow investigation into genotype × time interactions, while optimally accounting for spatial and temporal correlation.

Implications. The models provide improvements on current approaches and hence will result in more accurate genetic predictions in multi-assessment perennial crop variety selection trials.

Genetic diversity is crucial for crop improvement in any breeding program. Cowpea is an important indigenous grain vegetable legume crop. The crop has a significant potential to improve food and nutritional security in sub-Saharan Africa (SSA), and family income for resource poor famers. Cowpea is a source of proteins, vitamins (folate, thiamine and vitamin C), minerals (Fe, Zn, Mn and Ca) and amino acids such as lysine and tryptophan, hence, has a high potential for combating nutrient deficiencies. The SSA countries, including South Africa, have been experiencing many dry seasons, which have negatively affected agricultural production and productivity. Cowpea has a long taproot with the ability to grow in arid and semi-arid regions; however, lasting exposure to severe droughts will result in significant yield and grain quality reduction. There has been limited progress in drought tolerance research in cowpea due to the complexity of this trait, as it involves numerous genes, which in turn are affected by environmental conditions. It is therefore important to review research done on the nutritional, phenotypic and genotypic diversity of cowpea and the importance of diversity when breeding for complex quantitative traits such as drought tolerance and yield. The review will also outline the important omics tools used for drought tolerance breeding, cultivar development and as reference for future cowpea breeding.

Context. Breeding for early maturity and higher yield is the principal objective in genetic improvement of Indian soybean. Yellow Mosaic Disease caused by Mungbean Yellow Mosaic India Virus (MYMIV) causes 80% yield loss in soybean.

Aims. This study aimed to develop early maturing, MYMIV resistant and high yielding soybean genotypes for enhancing soybean production and expanding the land area under cropping.

Methods. MYMIV resistance was introgressed from G. soja in to a widely adaptable cultivar JS 335 through a series of four generations of backcrosses and by evaluating derived progeny against MYMIV at a disease hot spot.

Key results. An extra-early maturing (71 days) genetic stock called NRC 252 was developed, which can be a potential gene donor in breeding for early maturing soybean varieties. Introgression lines YMV 1, YMV 2, YMV 11 and YMV 16 with MYMIV resistance and higher yield performance over recurrent parent and other check varieties were identified and characterised. Biplot analysis, assessing the main effect of genotype and the interaction of genotype with environment, revealed an ideal genotype with respect to 100-seed weight and grain yield that was also promising under sugarcane-soybean intercropping system in spring season.

Conclusions. Alleles from wild type soybean could improve yield attributing traits and MYMIV resistance in cultivated soybean. Improved genotypes such as YMV 1, YMV 2, YMV 11 and YMV 16 were found superior to the recurrent parent JS 335 as well as other check varieties.

Implications. The genotypes developed in the present study will help in reducing the damage caused by MYMIV disease and expansion of the area of soybean cultivation through intercropping with sugarcane.

Context. Drought is a common abiotic stress affecting crop yield and quality worldwide. Sugar beet (Beta vulgaris L.) is a temperate crop that contributes greatly to world sucrose production and is affected by frequent drought. MicroRNAs (miRNAs) have been demonstrated to play an important role in plant abiotic stress responses. Protein-coding genes associated with drought resistance have been identified in sugar beet; however, studies on miRNAs involved in drought stress response are lacking.

Aims. The present study focused on analysing miRNAs in sugar beet and their roles in drought stress response.

Method. Small-RNA libraries were constructed from leaves of plants subjected to drought stress and well-watered conditions. High-throughput sequencing and bioinformatics analysis were used to investigate the genome-wide quantity of miRNAs and identify possible drought response regulatory effects.

Key results. Deep sequencing identified 49 known miRNAs and 59 new miRNAs. According to the Kyoto Encyclopaedia of Genes and Genomes (KEGG), the sulfur relay system was significantly enriched under drought stress. Co-regulated pairs between miR156a-5p, novel_18 and novel_41, and their target genes BVRB_6g136190, BVRB_009610 and BVRB_6g136680 were observed, suggesting a negative feedback modulation involved in the miRNA pathways.

Conclusions. Our results indicate that certain metabolic pathways such as the sulfur relay system are activated under drought conditions.

Implications. The results aid understanding of the mechanisms of drought response at the molecular level and may enable tools to be devised that enhance drought resistance in sugar beet.

Increasing plant resistance to biotic and abiotic stresses may help to address global food insecurity. We review small RNA (sRNA) research and consider the potential of sRNA-based technologies as strategies to enhance plant resistance to environmental stresses. sRNAs are essential non-coding signalling molecules 21–24 nucleotides in length that are involved in various reproduction, defence and plant development processes. sRNAs guide regulatory processes during development and environmental adaptation at the DNA or RNA level in various eukaryotic organisms. They control gene expression in eukaryotes via a process commonly termed RNA silencing. sRNAs are responsible for suppressing some pathogenic genes in eukaryotes and pests. This suppression offers the potential to protect plant growth and development through a new generation of eco-friendly RNA-based fungicides or insecticides that are specific in their target and can easily control multiple diseases simultaneously. This review focuses on sRNA production in crop species, the role of sRNAs in plant responses to a range of stresses, and their prospective applications, highlighting sRNA-based technology and applications in crops under stress. This review could serve as a reference for future researchers working on small RNAs and the roles they play in plant response to environmental stresses.

Context. Wild oats (Avena spp.), brome grass (Bromus spp.) and barley grass (Hordeum spp.) are significant grass weeds of crop production in south-eastern Australia. The presence of herbicide resistance in these weed species is a major limiting factor on both productivity and profitability.

Aims. We aimed to determine the distribution of herbicide resistance in these weed species across south-eastern Australia.

Methods. Several surveys were conducted in randomly selected fields across four states in south-eastern Australia over a 5-year period, collecting 663 wild oats, 366 brome grass and 262 barley grass samples that were screened for resistance with up to five different herbicide groups or subgroups.

Key results. In wild oats, resistance was most common to clodinafop-propargyl (‘fop’ ACCase inhibitor), with 22% of samples resistant and resistance detected in all regions except Tasmania. Resistance to sulfonylurea herbicides (ALS inhibitors) was less common with 7% of samples resistant, but regionally more variable. For both brome grass and barley grass, a greater proportion of samples was resistant to the sulfonylurea mesosulfuron-methyl, at 24% and 19%, respectively, than to quizalofop-ethyl (‘fop’ ACCase inhibitor).

Conclusions. Resistance was recorded in all three species, with differences in the extent of resistance among herbicide groups and regions. Overall, a higher than average frequency of wild oats resistance to clodinafop-propargyl was found in regions of New South Wales and of brome grass and barley grass resistance to mesosulfuron-methyl in regions of South Australia. However, for all species some herbicides were still effective on all samples.

Implications. The presence of significant herbicide resistance in these weed species indicates that management decisions need to include consideration of resistance to enable successful control measures.

Context. Defoliation management by grazing or clipping, combined with nitrogen (N) fertilisation, can increase forage production in tropical grasses. Use of pasture canopy height as a practical tool for monitoring forage mass and accumulation has been proposed because of the relationship between height and canopy light interception. However, this relationship can vary due to variations in canopy structural changes and N supply.

Aims. Our objectives were to study canopy structural responses and forage accumulation of grazed Zuri guineagrass (Megathyrsus maximus) under rotational stocking.

Methods. Combinations of two pre-graze canopy heights (55 and 75 cm) and two N fertilisation rates (150 and 300 kg N ha⁻¹ year⁻¹) were used during two consecutive years. Cattle grazed the pastures to 50% of pre-graze height.

Key results. Regardless of N rate, pastures managed at 75 cm always reached 95% light interception at pre-graze. The 55 cm/300 kg N pastures underwent structural changes such as greater leaf proportion, tiller population density and specific leaf area, and smaller mean foliage angle, which resulted in 95% light interception at pre-graze. Forage accumulation was 20% greater for 75 cm pastures (22 120 kg DM ha⁻¹ year⁻¹) than 55 cm pastures. Pastures receiving 300 kg N ha⁻¹ year⁻¹ had 38% greater forage accumulation than those receiving 150 kg N ha⁻¹ year⁻¹.

Conclusion. Zuri guineagrass pastures should be defoliated when canopy height reaches 75 cm owing to greater forage accumulation, but can be grazed at 55 cm when N is applied at 300 kg ha⁻¹ year⁻¹.

Implications. Zuri guineagrass can be managed with shorter pre-graze canopy height; when grazed at 55 cm and with 300 kg N ha⁻¹ year⁻¹, there is no negative effect on forage accumulation, allowing for shorter rest periods.

Context. Introducing legumes into grass-based forage systems may increase herbage nutritive value while reducing the need for inorganic nitrogen fertilisation. Grass–legume intercrops may also enhance herbage yield stability.

Aim. We evaluated agronomic and nutritional traits of elephant grass (Cenchrus purpureus Schum.) genotypes grown as monocrops and mixed with butterfly pea (Clitoria ternatea L.).

Methods. Elephant grass genotypes, two tall (Elephant B and IRI-381) and two dwarf (Mott and Taiwan A-146 2.37), were grown as monocultures or intercropped with butterfly pea in a 2-year trial. Herbage accumulation, yield stability, botanical composition and chemical/bromatological variables were evaluated.

Key results. Herbage accumulation was highest (P < 0.001) in Elephant B under monocropping (21.9 t/ha.year); however, this treatment revealed the lowest yield stability over harvest times (σ_i² 5.59). All intercrops were more stable than grass monocrops (mean σ_i² 0.66 vs 2.55). Higher (P < 0.001) concentrations of herbage crude protein were found in intercrops than monocrops (mean 113 vs 90 g/kg). Intercrop herbage lignin contents (mean 57 g/kg) and protein fraction C (mean 61 g/kg) were higher than those in monocrops. Dwarf Mott had higher (P = 0.001) digestible dry matter concentration than dwarf Taiwan (755 vs 745 g/kg).

Conclusions. Dwarf Mott genotype has outstanding nutritive value because of its higher leaf:stem ratio. Butterfly pea legume added to elephant grass crop in cut-and-carry systems improves herbage yield stability by reducing seasonal effects.

Implications. Intercropping butterfly pea in grass-based systems enhances yield stability, allowing herbage harvest with good nutritive value.

Context. Biological nitrogen (N) fixation through the rhizobia–legume symbiosis is a sustainable and cost-effective source of N for agriculture. In New Zealand (NZ), white clover (Trifolium repens) is a key component of pastures and rhizobial inoculation of clover is widely used. The current commercial inoculant for white clover, TA1, was isolated in Australia in the 1950s and may not be the best partner for modern white clover cultivars.

Aims. To identify Rhizobium leguminosarum bv. trifolii (Rlt) isolates suitable for use in NZ pastures.

Methods. The symbiotic potential of >230 isolates collected from throughout NZ was evaluated in plant bioassays. Selected isolates were further evaluated in pot and field trials.

Key results. Approximately 40% of NZ isolates supported better clover growth than TA1 under N-limited conditions in vitro. Of 24 Rlt isolates evaluated in a glasshouse trial, five produced significantly higher clover biomass than TA1. Three (S11N9, S20N7, S4N6) of nine isolates evaluated in two field trials in 2018–2019 significantly increased clover growth (12–38%) compared with paired uninoculated clover at several harvests, whereas inoculation with TA1 did not improve yield. In a third trial in 2020, S11N9 and S20N7 increased clover growth compared with the uninoculated control at two of three harvests; S4N6 performed better than TA1 at one harvest. When tested with four white clover cultivars, five Rlt isolates had higher symbiotic potential than TA1.

Conclusions. Inoculating white clover would be beneficial if improved inoculant isolates were available.

Implications. We recommend some NZ Rlt isolates could be developed into commercial inoculants to improve white clover performance in NZ.

Context. Dairy pasture production is reliant on fertiliser to supply nitrogen (N); however, fertiliser N-use efficiency (FNUE) is low and N can be lost to the environment.

Aims. The aim of this study was to track the fate of N fertiliser applied in a pasture system of ryegrass (Lolium multiflorum, temperate grass) oversown into kikuyu (Pennisetum clandestinum, tropical grass).

Methods. We used ¹⁵N-labelled urea to track the residual plant uptake of a one-off application of ¹⁵N over three pasture cuts subsequent to the first cut in the kikuyu growing season from February 2018 to April 2018 (Experiment 1), followed by total soil and plant recoveries of ¹⁵N over a 12-month period (Experiment 2). Total N treatment rates were 0, 120, 240 and 480 kg N ha⁻¹ year⁻¹, consisting of application events of 40 kg N ha⁻¹. In Experiment 1, ¹⁵N was applied only at the first fertilisation, whereas in Experiment 2, ¹⁵N-labelled urea was applied at each fertilisation event.

Key results. In Experiment 1, uptake of residual ¹⁵N fertiliser in the pasture biomass was <6%. In Experiment 2, FNUE was 29–32% and unaccounted ¹⁵N fertiliser was 22–142 kg N ha⁻¹, across the 120, 240 and 480 kg N ha⁻¹ year⁻¹ treatments.

Conclusions. Recovery of ¹⁵N residual fertiliser did not increase with N rate and was attributed to the mass increase in soil ¹⁵N recovery. FNUE in the pasture did not decrease with N rate. Unaccounted ¹⁵N increased with N rate.

Implications. Existing and alternative N and pasture management strategies such as clover and multi-species pasture need to be implemented and explored to reduce the amount of unaccounted N in dairy pasture production.

Context. Limitations to crop yield due to subsurface (5–15 cm depth) compaction layers (>2 MPa) and subsurface acidity (pH_Ca <4.8) have frequently been reported on the non-sodic soils of south-eastern Australia, but amendment studies have been limited in number and inconsistent in the extent and longevity of any response.

Aim. We tested the hypothesis that amendment of subsurface acidity and compaction would lead to increased grain yield.

Method. We investigated crop response to the alleviation of these combined subsurface soil constraints by using deep ripping and dry limestone injection to 30 cm depth over 3 years in a canola–cereal sequence.

Key results. Deep tillage and injection of limestone into the soil both failed to produce significant grain yield responses in any year, despite the reduction of soil strength and increase in pH in subsurface layers. Early vegetative growth sometimes responded to the treatments, but the loss of stored soil water during drier than average seasons appeared to limit grain response. However, we also observed that a proportion of plant roots penetrated these relatively thin constraint layers in unamended soils.

Conclusions. Amelioration of subsurface acidity and compaction does not necessarily increase grain yield.

Implications. The effects of subsurface acidity and compaction should be tested on other species and during varying rainfall deciles. Given the potentially large resource requirements for deep amendment of soils, we propose that the selection of tolerant species and cultivars might be more effective in the short term.

Context. Knowledge gaps exist for the interference of Avena ludoviciana and Argemone mexicana in chickpea grown in eastern Australia.

Aims. This research aimed to examine the effect of different interference levels of A. ludoviciana and A. mexicana for their potential to cause yield loss in chickpea.

Methods. Experiments were conducted in a randomised complete block design with five weed infestation levels of both weeds (none, low, medium, high, and very high) in three replications.

Key results. Infestations of A. ludoviciana and A. mexicana at 15 and 17 plants m⁻² caused an 83 and 48% reduction in chickpea yield, respectively, compared with weed-free situations. Based on the regression model, a 50% yield reduction of chickpea occurred at 10 and 17 plants m⁻² of A. ludoviciana and A. mexicana, respectively. Based on the modified hyperbolic model, maximum seed production of A. ludoviciana and A. mexicana in chickpea at an infestation level of 1 plant m⁻² was estimated at 366 and 7800 seeds m⁻², respectively. At crop harvest, seed retention of A. ludoviciana and A. mexicana was greater than 50 and 90%, respectively.

Conclusions. A. ludoviciana and A. mexicana infestation in chickpea caused a substantial reduction in crop yield. High seed retention in A. mexicana and A. ludoviciana in chickpea suggests the possibility to manage these two weeds through harvest weed seed control.

Implications. The information generated from this study could help in strengthening integrated weed management in chickpea.

Context. Carbon (C) and nitrogen (N) transformation processes in soils play an important role in the fluctuation of soil pH. Incorporation of chitosan and crop straws, byproducts from fishery and agriculture, into acidic soils can increase soil pH through decarboxylation, decomposition, N immobilisation and ammonification.

Aims. The study was designed to evaluate the transformation of organic N and C from chitosan and/or crop straws and their effects on soil physicochemical properties.

Methods. Chitosan, rice straw and maize straw were incubated with two acidic Ultisols from Langxi (Soil 1) and Yingtan (Soil 2) differing in initial pH. Six treatments were prepared in triplicate: control (no amendment), 4% chitosan, 4% rice straw, 4% maize straw, 2% chitosan + 2% rice straw, and 2% chitosan + 2% maize straw. Soil pH, N transformation and CO₂ evolution were estimated at different time intervals.

Key results. After 40 days of incubation, control soil pH decreased by 0.35 and 0.32 units for Soils 1 and 2, respectively. Rice straw, maize straw, chitosan, rice straw–chitosan and maize straw–chitosan significantly increased soil pH by 0.51, 0.17, 2.27, 1.78 and 2.02 units for Soil 1, and 0.71, 0.16, 0.67, 0.49 and 0.68 units for Soil 2 (P < 0.01). The respective treatments decreased exchangeable acidity by 62%, 51%, 95%, 95% and 95% for Soil 1 and 75%, 69%, 88%, 88% and 87% for Soil 2. In treatments containing chitosan, the pH increase resulted from ammonification of organic N and mineralisation of organic C, with the effect higher in Soil 1 than Soil 2.

Conclusions. Amending acidic soils with chitosan and crop residues can effectively increase soil pH and slow soil acidification rate.

Implications. This study provides useful information for amelioration of acidic soils.