Adequate phosphorus (P) nutrition underpins cereal production in Australia and soil tests are commonly used to adjust fertiliser rates. The critical soil test values (i.e. required to achieve 90% of maximum yield) used for fertiliser recommendations have been derived from historic fertiliser trials sown mainly in May and June, with sowing date not considered in the interpretation of the critical values. However, the availability of long-season wheat cultivars has meant that crops can now be sown earlier. Experiments were conducted to investigate the effect of sowing time on optimum P rates for yield. Bread wheat (Triticum aestivum L.) cvv. Mace and Trojan were grown at five P rates at three sites in the Mid-North and Yorke Peninsula of South Australia, on alkaline calcareous soils, in each of 2 years. Both varieties showed similar responses to P. Crops sown in late April–early May often had a low optimum P rate, and there was a general trend for the optimum P rate to increase with later sowing. However, early sowing reduced the optimum P rate only when April rainfall was high. Grain yield responded positively to increases in vegetative growth from P fertiliser, and the optimum P rate for vegetative growth and grain yield were correlated. Early sowing increased grain P concentrations, and P removal rates were similar to, or greater than, those of later sown crops. Sowing in April–early May can reduce the P requirements of wheat, but there is an increased likelihood of a negative P balance; therefore, monitoring of soil P reserves will be required. A relationship between the optimum P rate for yield and the partial nutrient balance may provide a benchmark to help manage P.

Emmer wheat (Triticum turgidum ssp. dicoccum) is an important gene source for wheat improvement but less studied in crosses with its descendant species durum (Triticum turgidum ssp. durum), especially in respect to the type of genetic components, intergenic interactions and the genetic mechanisms governing responses to drought. In this study, generation means analysis was performed using F1, F2, BC1P1 and BC1P2 from two different crosses of emmer × durum. Seeds were planted in a RCBD design with three replications under two water regimes. Results showed that there was a highly considerable difference between generations for all studied traits. The presence of significant mean parameter for all the traits, indicated the quantitative inheritance of the traits. Estimating the number of effective genes, polygenic control of the traits were confirmed. In moisture stress condition, epistatic effect for grain yield and yield-related traits illustrated the importance of epistasis in plant adaptation and performance stability. The additive × additive effect, which is fixable, was remarkable in both crosses. Under both water regimes, narrow-sense heritability was relatively high and estimates of gain from selection were positive for most of the traits. Among generations studied, the backcrosses were superior for drought tolerant indices. Based on the results, emmer wheat seems to have genetic potential for durum improvement.

Genetic analysis of seed yield is important in the breeding of high-yielding cultivars in soybean (Glycine max (L.) Merr.). Generally, the number of quantitative trait loci (QTLs) associated with seed yield, even in a single population, is high, and thus, the effect of each QTL is small. Lodging tolerance is an important trait that affects yield because soybean plants with higher aboveground weights are easily lodged. We previously identified eight QTLs associated with seed yield and a QTL associated with lodging tolerance, qLS19-1, by using a recombinant inbred line (RIL) population derived from a cross between Japanese cultivars Toyoharuka and Toyomusume. There were significant positive correlations over 3 years between seed yield and the number of favourable alleles at QTLs associated with seed yield in the RILs. The aim of this study was to develop high-yielding lines by using marker-assisted selection for seed yield and lodging tolerance. Six pyramiding lines with favourable alleles at seven QTLs associated with seed yield and qLS19-1 were developed from a cross between two RILs in the same population. The seed yields of six pyramiding lines tended to be greater than those of Toyoharuka (114–124%) and Toyomusume (108–117%) in a 2-year yield trial. Four of the six pyramiding lines produced significantly higher yields and were later maturing than both Toyoharuka and Toyomusume. Our results suggest that marker-assisted selection for seed yield and lodging tolerance in the same population will be effective for high-yield breeding.

Gypsum (CaSO₄.2H₂O) decreases the harmful effect of soil acidity on plants and provides calcium (Ca) and sulfur (S) for plant nutrition. Setaria grass (Setaria anceps Stapf) and black oat (Avena strigosa Schreb.) are forage grasses that are tolerant of low soil fertility and may be suitable as inter-row crops for Satsuma mandarin (Citrus unshiu Marc.) grown organically on Oxisol soils, which may suffer low native fertility and high acidity. We evaluated the effect of gypsum application to a low fertility soil from subtropical Brazil on soil chemical fertility, growth and plant nutrition of Satsuma mandarin, and plant biomass yield and soil nutrient extraction of setaria grass and black oat cultivated between the orchard rows, in the absence of soluble industrial (NPK) fertilisers. The entire experimental field was limed, and ground natural phosphate rock was applied. During planting of the Satsuma mandarin, organic manure and ground natural phosphate rock were mixed with soil and placed in each planting hole. Two agricultural gypsum treatments were applied: one without gypsum (control), and the other with gypsum at 6 t ha⁻¹. After 12 months, gypsum reduced the level of aluminium (Al³⁺) and increased Ca²⁺ at soil depth 0–40 cm, and increased S-SO₄²⁻ at soil depth 0–60 cm. Other soil chemical components (pH, phosphorus, potassium, magnesium and micronutrients) were not affected by gypsum application. Gypsum did not affect growth of Satsuma mandarin, but increased leaf S concentration. Between the rows, gypsum decreased nitrogen extraction by setaria grass and increased Ca and S extractions by black oat. Biomass yield and nutrient extraction by the studied forage grasses were satisfactory, considering the poor soil fertility conditions. Setaria grass exhibited higher efficiency in recycling nutrients from the chemically poor soils than black oat. In general, setaria grass and black oat can be used as inter-row forage grasses for organic orchards of Satsuma mandarin, where there are restrictions on use of soluble industrial fertilisers.

Context. Perennial forage grass species are often grown with limited water following establishment and rely on accessing water deep in the soil profile to survive. Aim. This study aimed to characterise bermudagrass (Cynodon spp.) genotypes with rapid vertical root growth associated with post-establishment survival.Methods.Twelve bermudagrasses representing genotypes from diverse climate zones in Australia were established in rhizotrons to analyse the stability in genotypic variation in root and shoot growth in winter and summer experiments. Genotypic rank of root length, leaf area, and root dry weight were consistent in both seasons.Key results Bermudagrass genotypes exhibited different traits correlated with root vertical growth rate and inconsistency of genotypic rank of shoot growth. During winter establishment, the rate of root depth development (RRDD) (r = −0.64) was correlated with the proportion of root length that became inactive, that was likely due to seasonal root death in winter conditions; during summer establishment, RRDD was correlated with tiller appearance rate (r = 0.45) and root distribution to 10 cm depth (r = −0.62). Shoot dry weight was correlated with photosynthesis (r = 0.85) and transpiration (r = 0.79) in summer, but not in winter. RRDD (r = 0.75, winter and r = 0.77, summer) was correlated with drought resistance index, previously analysed under field conditions.Conclusions and implications. Genotypes from the Mediterranean climates in Australia showed rapid growth of roots and shoots in both seasons and have the greatest potential for broader application for forage production in variable environments.

Assessment of the relative performance of white clover (Trifolium repens L.) cultivars, using multi-year and multi-location seasonal growth trials, is key to identification of material with specific and broad adaptation. This paper is based on a multi-year and multi-location study of 56 white clover entries comprising 14 commercial cultivars and 42 experimental synthetic lines evaluated for seasonal growth under rotational grazing across four locations in New Zealand over 4 years. The four locations (and animals grazing) were: Kerikeri (beef cattle), Aorangi (beef cattle), Ruakura (dairy cattle), Lincoln (sheep). Significant (P < 0.05) genotypic variation among the 56 entries, and genotype × year, genotype × location and genotype × season interactions, were estimated. We were able to identify cultivars and experimental synthetics with specific and broad adaptation to the three grazing management types. Cvv. AberDance, Apex, Demand, Prestige, Quartz and Riesling, with leaf size ranging from small to medium–large, showed highly above-average performance under sheep grazing. Synthetic lines 15 and 45 also had highly above-average performance under sheep grazing. Cvv. Legacy and Kopu II showed above-average performance under cattle and dairy grazing. Synthetics 15, 48, 49, 44, 22 and 18 and cv. Quartz had above-average performance under all three grazing managements. Synthetics 27, 33 and 38 had highly above-average performance across all three grazing managements and were superior to all 14 cultivars evaluated. Several of these superior synthetics are being tested across multiple grazing environments. Among the 14 cultivars evaluated, Legacy and Quartz showed superior seasonal growth performance across the three grazing managements. Quartz is being evaluated in several on-farm trials across temperate regions of the world.

The native budworm, Helicoverpa punctigera (Wallengren), is an important economic insect pest of cotton and other crops. It is widely distributed in Australia and has been recorded on a range of host plants including native, non-crop hosts in inland regions. To date, there are few records of its occurrence on plants with the C₄ photosynthetic pathway. Here, we assessed the oviposition preferences of H. punctigera for naturally occurring C₃ and C₄ plants under glasshouse conditions, to establish their potential as hosts. We conducted bioassays on two C₄ plants, saltbushes Atriplex nummularia Lindl. and Atriplex vesicaria Heward ex Benth.; and two C₃ plants, legumes Medicago polymorpha L. (burr medic) and Cullen cinereum (Lindl.) J.W.Grimes (annual verbine). The two C₄ plants attract egg laying in the field; however, C₃ plants are the preferred hosts. Ovipositing females showed a preference for the C₃ over the C₄ plants but oviposition occurred on both. Of the C₄ plants, females preferred to oviposit on A. nummularia (77%) over A. vesicaria (24%) in both a multi- and two-choice test. In addition, ovipositing females preferred the upper leaf surface of A. nummularia (68%) and the under leaf surface of A. vesicaria (64%) as their oviposition site. Our findings suggest that under field conditions, when C₄ plants such as saltbushes grow near C₃ plants, as occurs in inland regions, the C₄ plants could receive eggs along with the C₃ plants, enabling the initial stages of larval recruitment to occur in C₃ plants.

Perennial ryegrass (Lolium perenne L.) is a widely sown pasture species in temperate regions. Under heat and moisture-deficit stress, its production is suppressed and tiller mortality increases, particularly when plants are simultaneously exposed to other stresses such as intense defoliation. We investigated the effects of extended grazing exclusion periods in spring and summer on herbage and soils of rotationally grazed, perennial ryegrass-dominant pastures at a summer-wet site and a summer-dry site in sheep and beef hill country in New Zealand. Treatments comprised ‘grazed’ (conventional rotational grazing), ‘early opening’ (grazing exclusion from mid-spring to mid-summer to allow perennial ryegrass to flower), and ‘deferred grazing’ (grazing exclusion from mid-spring to late summer to allow perennial ryegrass to flower and set seed). At both sites, deferred grazing increased perennial ryegrass tiller density and total vegetation cover, and reduced the abundance of broadleaf species and Pseudopithomyces chartarum spores for up to 15 months after exclusion compared with the grazed control. Herbage production was reduced during the deferred period but there was a growth surge thereafter so that herbage production over the study period was similar in the deferred and grazed treatments. Pasture nutritive values were lower in the deferred than the grazed treatment during the exclusion period but were similar in all treatments by the end of the following winter. In the autumn after deferring, seedlings contributed ∼50% of the perennial ryegrass tillers present at the summer-dry site but only ∼10% at the summer-wet site, where regrowth tillering of existing plants contributed a high proportion of the perennial ryegrass tillers present. Overall, early opening had few effects on the pasture, whereas deferred grazing had numerous positive effects on the pasture but only short-term effects on soil quality.