The ability to utilise foliar-applied phosphorus (P) as a strategy to increase the P status and yield of grain crops grown in dryland regions with variable climates is attractive. Several P formulations with varying pH, accompanying cations and adjuvants were tested for their effectiveness as foliar fertilisers for wheat (Triticum aestivum L.) plants, first under controlled and then under field conditions. Experiments under controlled conditions suggested that several formulations with specific chemistries offered promise with respect to wheat fertiliser-P recovery and biomass responses. These formulations were then evaluated in two field experiments, and although wheat grown at the sites showed substantive responses to soil-applied P, there was no significant grain-yield response to foliar-applied P. Following the limited responses to foliar-applied fertiliser in the field, we used an isotopic dilution technique to test the hypothesis that the variation in responses of wheat to foliar addition of P could be explained by a mechanism of substitution, whereby root P uptake is downregulated when P is taken up through the leaves, but this was proven not to be the case. We conclude that foliar P application cannot be used as a tactical fertiliser application to boost grain yield of wheat in dryland regions.

Sustaining diverse, yet productive crop sequences that integrate break crops such as canola (Brassica napus L.) remains a critical challenge for farming systems in low-rainfall cropping environments. Recent advances in canola productivity through early sowing, understanding of critical stress periods, hybrid cultivars and improved nitrogen (N) fertilisation offer promise under many conditions but require careful adaptation for risky, low-rainfall environments. A series of eight experiments was implemented over four growing seasons (2015–18) in the low-rainfall environments of southern Australia to test combinations of sowing date, cultivar selection and N-management strategies. Simulation modelling extended the field experiment results, enabling a simple, whole-farm profit–risk analysis across growing season deciles. The aim was to identify combinations of practices where the potential production and risk were understood, thereby assisting management decisions in low-rainfall cropping systems. Earlier sowing (April) was generally beneficial but only where seasonal conditions led to successful establishment, meaning that the best fit for canola in low-rainfall environments is as an opportunity crop. A hybrid cultivar (triazine tolerant) did not provide a yield advantage in an early experiment, but productivity increases were measured with a modern hybrid cultivar (Clearfield) in a later experiment. Profit-risk analysis suggested that a yield advantage of >20% over open-pollinated cultivars needs to be sustained across the full range of season deciles to generate economic advantage. Although there was relative insensitivity to the timing of N application, an adequate dose of N, either through fertiliser or legume crops, was critical to improve canola productivity. We conclude that opportunities exist to make significant gains in yield (by up to 110% compared with current standard practice) and profit–risk outcomes (∼30% increased gross margins across all season types) for canola in low-rainfall environments by using a package of agronomic management decisions that includes early sowing on genuine establishment opportunities, hybrids that offer sustained yield benefits, and matching N dose from both fertiliser and legume crops to yield potential of the soil type and seasonal outlook.

Plant genetic improvement may be done traditionally by selecting the most appropriate genotypes based on heritability, stability, genetic distance and other genetic parameters. In this paper, the analytical hierarchy process (AHP) with some modifications was used as a new multivariate method for determining the capability of elite tomato (Solanum lycopersicum L.) genotypes to form the next-generation breeding population. Modified AHP is performed in three steps: (i) aligning traits and genotypes, (ii) calculating weights of traits, and (iii) calculating weights of genotypes. Fruit quality and yield were evaluated in 20 F₂ tomato families cultured along with their parents in a randomised complete block design with three replications in the research field. The traits fruit yield, plant cluster number and fruit number per plant were identified as the most effective for ordering genotypes. Four families were identified as the best (selection among families), and the best individuals selected from a total of 60 individuals (selection within families) almost all belonged to these four families. Because of the use of genetic parameters in modified AHP, the selected genotypes were the best choices with respect to fruit yield, lycopene content and capability to create a breeding population.

In order to develop a better understanding of some yield components, the response of three modern cotton (Gossypium hirsutum L.) cultivars to increasing nitrogen (N) fertiliser application was assessed for lint percentage (LP) and seed weight, as well as seed protein and oil concentrations. Application of N fertiliser led to decreased LP in all three cultivars (by 1.5 percentage points), even if the N-fertiliser rate was above the optimum rate. There was a strong negative correlation between LP and seed mass because seed mass is a component of LP. Seed protein concentration increased, and seed oil concentration decreased, with increasing N fertiliser application. Seed germination was improved in seeds with higher oil concentration; therefore, seed produced with high N fertiliser had reduced seed vigour. It was concluded that little scope exists for further lint-yield increase via LP. For cultivars with small seeds, an integrated system across seed production and crop agronomy can achieve satisfactory seed vigour in the field while also achieving high commercial yields. Future improvements in yield will come from alternative and more complex yield components such as growth habit.

The conversion of natural forest to oil palm (Elaeis guineensis Jacq.) plantation is perceived as a threat to biodiversity conservation. The aims of this investigation were to assess variation in soil physico-chemical parameters and macroinvertebrate structures following the conversion of secondary forests to oil palm plantations, and to understand what to expect with the aging of the plantations. We hypothesised that soil properties would be improved with respect to biodiversity conservation with the aging of the oil palm plantations. Sampling was carried out in secondary forests, and in 13-, 20- and 39-year-old oil palm plantations at the La Mé Station, Côte d’Ivoire. Three sampling areas were established in each land-use type and age class, for a total of 12 sampling areas. Over a 50-m transect, litter-dwelling macroinvertebrates were sampled by using pitfall traps, and topsoil (0–10 cm) macroinvertebrates by using monoliths (50 cm by 50 cm by 10 cm), following the modified ‘Tropical soil biology and fertility’ method. Soil physical and chemical parameters were characterised. The results showed that the conversion of secondary forests to oil palm plantations was characterised by changes in soil macroinvertebrate density (–30%), taxonomic richness (–37%) and functional groups (–17%), as well as soil bulk density (+14%) and water content (+16%), after ∼39 years of conversion. Soil organic carbon, total nitrogen and organic matter increased with the aging of plantations, and reached conditions similar to those of secondary forests. The human interference imposed on macroinvertebrate communities during site preparation and planting was not compensated by the reduction in the soil-degradation index over time. The results have implications for implementation of conservation agriculture and the related management practices.

Germplasm of the perennial pasture grass Phalaris aquatica L., from Sardinia, Italy, is a potentially valuable source for grass breeders owing to climatic similarities to regions where P. aquatica is used, a relatively high incidence of acidic soils, and exposure to prolonged grazing pressure. At field sites in south-eastern Australia, Sardinian accessions were compared as spaced plants and drill-rows with accessions from southern Europe and north-western Africa and with commercial cultivars. They were also evaluated in grazed swards at three sites over 4 years under conditions that challenge persistence, including heavy grazing pressure, acid soils and drought. Morphologically, the accessions were comparatively dense, fine and short, with similarities to southern European accessions and cultivars of the cv. Australian type. However, they were earlier heading and more summer-dormant, particularly those from southern Sardinia. In drill-rows, Sardinian accessions were later heading and less productive in winter than accessions from Morocco. In swards, Sardinian accessions had lower seedling vigour and winter growth potential than modern winter-active cultivars. However, they were dense and persistent under high grazing pressure, and some accessions survived better than all cultivars on an acid, low-fertility soil. Developing cultivars that are superior to the cv. Australian type with acceptable seed production and alkaloid levels presents a challenge to breeders. However Sardinian germplasm offers a range of maturity times combined with higher levels of summer dormancy and a grazing-tolerant morphology, attributes that may expand the area of adaptation of the species into the hotter and more drought-prone margin.

Conyza bonariensis (L.) Cronq. (syn. of Erigeron bonariensis L.) is a difficult-to-control summer weed species in the cropping belt of south-eastern Australia. Herbicide resistance may be affecting the ability to control C. bonariensis in the agricultural region of north-eastern Victoria; therefore, a survey was conducted to evaluate resistance to herbicides from several mode-of-action groups. Of the populations collected, 40% were resistant to glyphosate at 1080 g ha^–1. Chlorsulfuron failed to control any of the populations collected. Further research identified multiple herbicide resistance to glyphosate, chlorsulfuron, metsulfuron-methyl and sulfometuron-methyl in five of nine populations fully characterised. Resistance was not found to 2,4-D, clopyralid or paraquat. There was no correlation between prevailing land use and the frequency of glyphosate-resistant populations, suggesting that resistance had been selected in multiple production systems. The high frequency of resistance could explain the difficulty experienced in controlling C. bonariensis across north-eastern Victoria and demonstrates the importance of integrated weed management to manage this weed.