The market for high-quality organic bread wheat (Triticum aestivum L.) is increasing in New England, USA, providing opportunities for organic dairy farmers to grow this alternative cash crop. Our objective was to determine the sustainability of eight 3-year crop sequences compared with a perennial forage baseline in long-term (25-year), well-managed, medium-sized organic dairy farm simulations. Systems included wheat (spring or winter) preceded by maize (Zea mays L.) silage, a 1-year-old perennial forage grass, or soybean as well as maize silage followed by maize silage or soybean. Farm net return was highest for the entirely grass-based system (US$742.15 cow^–1). Higher winter wheat yields for soybean–wheat–grass resulted in 7% more income from feed sales ($1027) than spring wheat. Soybean followed by wheat reduced soil nutrient accumulation by 0.8 kg ha^–1 year^–1 for phosphorus runoff and leachate losses and for potassium accumulation (–17%); there was also a 4% reduction in water footprint (kg kg^–1 fat- and protein-corrected milk). Growing winter wheat provides long-term environmental and economic benefits, although for spring wheat, much of this benefit is lost. Use of maize silage in place of grass, winter or spring wheat, or soybean was less profitable. Most cropping system scenarios were less economically favourable than producing and feeding exclusively grass silage. However, inclusion of soybean increased economic benefits.

Nitrogen (N) is a key mineral element required for crop growth, yield and quality. Nitrogen-use efficiency (NUE) in crop plants is low despite significant research efforts. Excessive use of N fertiliser results in significant economic cost and contributes to environmental pollution. Therefore, it is crucial to develop crop varieties with improved NUE, and this requires efficient phenotyping approaches to screen genotypes under defined N conditions. To address this, 15 wheat (Triticum aestivum L.) varieties, grown under three N levels, were phenotyped for NUE-related traits under field conditions. Significant genotypic differences were observed in varieties having low to high responsiveness to N applications. The results suggest that basal low N can be used to screen wheat varieties that are less responsive to N, whereas N supply from 80 to 160 kg N ha^–1 could be used to screen high N-responsive varieties. Normalised difference vegetation index (NDVI) measured by using Crop Circle, and SPAD units measured by SPAD meter at heading stage, were well correlated with shoot dry biomass, grain yield, and shoot and grain N concentration, and could potentially be used as tools to phenotype different wheat varieties under varying N treatments. The data also demonstrated that NDVI and SPAD could be used to differentiate wheat varieties phenotypically for NUE-related traits. The prospect of utilising efficient, non-destructive phenotyping to study NUE in crops is also discussed.

Eight rice experiments were established at two sites in the Riverina district of south-eastern Australia in the 2012–13 and 2013–14 seasons. Two semi-dwarf rice varieties were drill-sown and nitrogen (N) fertiliser (urea) was applied at different rates at the 4-leaf stage before permanent water (pre-PW) and at panicle initiation (PI). The research assessed the impact of timing of N application on grain yield, compared the apparent N recovery of N fertiliser applied at the two stages, and determined an application strategy for N to obtain consistently high grain yields for current, semi-dwarf rice varieties when drill-sown. The apparent N recoveries achieved were 59% for N applied pre-PW and 25% for N applied at PI, averaged across years, sites, varieties and N rates. Grain yield increased significantly with increased rate of N applied at both stages, but the rate of increase from N applied at PI decreased as the rate of N applied pre-PW increased. The grain yield increase for N applied pre-PW was due to increased number of panicles at maturity and increased number of florets per panicle. Nitrogen applied at PI increased dry matter at maturity and number of florets per panicle. Application of N at PI increased grain yield over that when no N was applied; however, at low PI N-uptake levels, application of N at PI is not enough to achieve high grain yields. Therefore, sufficient N should be available to the crop from a combination of soil- and pre-PW-applied N for the crop to reach a level of N uptake at PI whereby high yields can be achieved. Nitrogen applied at PI did not appear to increase the potential for cold-induced floret sterility as much as pre-PW-applied N. Further research is required to confirm this in other seasons and for other rice varieties.

To achieve high productivity of labour and water in rice cropping, farmers in South Asia have recently shown more interest in dry direct-seeded rice (DSR). An understanding of physiological and biochemical traits associated with high grain yield and efficiency of nitrogen (N) use is important to the development of genotypes for DSR. We investigated this issue with rice genotypes adapted to DSR in response to N rates. A 2-year study was conducted in a factorial randomised complete block design with eight genotypes and two N rates (75 and 150 kg N ha^–1). Almost all of the physiological and biochemical traits studied (e.g. plant height, chlorophyll content, panicle weight, soluble sugars, starch) in DSR improved with increasing N from 75 to 150 kg ha^–1, resulting in a 6% increase in yield at 150 kg N ha^–1 relative to 75 kg N ha^–1. Partial factor productivity of N was highest for the genotype IET-23455 (72.4 kg kg^–1) and lowest for the genotype AAUDR (37.4 kg kg^–1). Our results suggest that genotypes such as IET-23455 can maintain grain yield at low N rates as N-efficient genotypes. The greater biochemical activity (nitrate reductase and glutamine synthetase, sugar, protein and proline) and higher photosynthetic N-use efficiency at low N rates could be used in selection for N-efficient rice genotypes for DSR.

Although soil salinity and potassium (K) deficiency are widespread in agricultural lands, there is a paucity of knowledge about the interactive effects of sodium (Na) and K on the growth and yield of major grain crops. In pot experiments, we examined salt tolerance of canola (Brassica napus L.), narrow-leafed lupin (Lupinus angustifolius L.) and wheat (Triticum aestivum L.), and crop K requirement under Na supply ranging from low to high. Plant growth and seed yield of all three crops were lower at 40 mg K/kg than at 100 mg K/kg soil. Although 100 mg Na/kg (4 dS/m in soil solution) had little effect on canola cv. Boomer and wheat cv. Wyalkatchem, the salt-treated narrow-leafed lupin cv. Mandelup died at 47 days after sowing, regardless of amount of soil K. In low-K soils, canola with 100 mg Na/kg and wheat with 50 mg Na/kg did not show K-deficiency symptoms and produced greater seed yield than plants with nil Na addition. At 100 mg K/kg, Na-induced reduction in growth and yield occurred only to plants with 200 mg Na/kg. However, at 160 mg K/kg, 200 mg Na/kg did not have an adverse effect. In canola and wheat, shoot K concentration increased and shoot Na concentration decreased with increasing amount of soil K; however, high soil K did not reduce shoot Na concentration in narrow-leafed lupin. The study showed that narrow-leafed lupin was very susceptible to salinity, whereas canola and wheat plants were relatively salt-tolerant. The stimulation of growth and yield in canola and wheat by low–moderate Na in low-K soils suggests partial K substitution by Na, and that adaptation of canola and wheat to salt-affected soils can be enhanced by high K supply.

Powdery mildew of brassicas, caused by Erysiphe cruciferarum, is an emerging threat to oilseed Brassica production in Australia. Resistance to powdery mildew was assessed in 112 current and historic Australian Brassica napus canola cultivars and five cultivars of B. juncea mustard cultivars under controlled environmental conditions. Only 18% of leaf area was infested by the end of the test on the most resistant cultivars, compared with means of up to 70% for the most susceptible cultivars as well as severe stem and pod infection. For B. napus, cultivars with the greatest potential for reducing the impact of powdery mildew in the field were Trooper, Bravo TT, Summit, Tumby, Narendra and Hyola 650TT, all ranked in the 10% of cultivars with the lowest leaf infestation (Area Under The Disease Progress Curve (AUDPC) <537) and with <10% of stem area infested. For B. juncea, the level of leaf infestation was lowest for Sahara CL and Xceed X121 CL (AUDPC 303 and 380 respectively), but the high levels of stem infestation (42% and 28% respectively) in these cultivars may reduce their usefulness in the field. The most resistant cultivars identified can be immediately deployed into regions where powdery mildew is prevalent, providing the canola industry with an immediate and effective option for management of this increasingly troublesome disease.

Constructed grasslands are primary restoration measures in areas with degraded natural grasslands. Grass–legume mixtures are chosen to obtain high production and forage quality; however, the photosynthetic and other traits of such mixtures are not well understood. In this study, we evaluated the effects of grass–legume mixtures on the growth and photosynthetic capacity of three forage crops over two growing seasons. Bromus inermis and Elymus nutans were grown as monocultures or in mixtures with Medicago sativa. We analysed forage yields, quality, gas exchange and chlorophyll fluorescence parameters. The grass–legume mixtures improved the forage yield, root : shoot ratio, and contents of crude protein and lignin. Compared with the monoculture, grasses in the mixtures had higher net photosynthesis, water-use efficiency (WUE), and leaf nitrogen (N) content, but lower carbon : N ratio, and distributed more absorbed light to photosynthetic electron transport and thermal dissipation. In the mixture, B. inermis had a higher light-saturation point, indicating high light-use efficiency. Elymus nutans had a lower light-compensation point and dark respiration rate, suggesting good shade tolerance. However, water deficits decreased biomass and photosynthetic capacity in the E. nutans–M. sativa mixture, suggesting that E. nutans was sensitive to soil moisture. The B. inermis–M. sativa mixture had greater and more consistent biomass and WUE.The grass—legume mixture is an important way to construct grasslands. We analysed forage yields, quality, gas exchange and chlorophyll fluorescence in the mixtures, finding that grass—legume mixtures improved forage production and photosynthetic capacity. The study provides a scientific basis for establishment of constructed grasslands with high yield and quality.

The canopy height (CH) at 95% light interception (LI) is a valuable defoliation frequency strategy used to handle variability in herbage accumulation throughout the year, mainly in C₄ grasses. Such a strategy has been adopted as an open pasture management index, but defoliation frequency and intensity remain unsolved issues for shade-grown forages. A field experiment was conducted for 2 years to determine the influence of tree canopy (Eucalyptus dunnii) shading and nitrogen availability (0 and 300 kg N ha^–1 year^–1) on CH at 95% LI of six perennial tropical forage species. The plots were cut at 95% LI, and the height of the residual sward was kept at 50% of the corresponding CH at 95% LI. The shade level ranged from ∼40% at the beginning of the experiment to ∼60% at the end of summer 2013. Variations in CH at 95% LI occurred because of shading and across seasons. The range of these variations was species-dependent. Overall, species growing under trees showed higher CH, except for Paspalum notatum and Megathyrsus maximus in the first year. There was a significant increase in the length of the sheaths and leaves, as well as a decrease in tiller density and leaf : stem ratio in plants growing under trees. Nitrogen also had an impact on CH; however, its application did not compensate the shade effect on CH. Therefore, our results suggest that greater CH should be considered in case of defoliated, shade-grown plants and that such strategy might change throughout seasons.

American sloughgrass (Beckmannia syzigachne Steud.) is a problematic grass that is widely distributed in wheat and oilseed rape fields in China. The herbicides fenoxaprop-P-ethyl and mesosulfuron-methyl failed to control B. syzigachne JCWJ-R populations collected from a wheat field in Jiangsu Province. Dose-response experiments showed that JCWJ-R was resistant to the acetyl-CoA carboxylase (ACCase) inhibitors fenoxaprop-P-ethyl (33.8-fold), haloxyfop-R-methyl (12.7-fold), clethodim (7.8-fold) and pinoxaden (11.6-fold), and to the acetolactate synthase (ALS) inhibitors mesosulfuron-methyl (15.9-fold), pyroxsulam (17.6-fold), flucarbazone-Na (10.7-fold) and imazethapyr (7-fold). Resistance to ALS inhibitors was due to a Pro-197-Ser mutation in the ALS gene and resistance to ACCase inhibitors was due to an Ile-1781-Leu mutation in the ACCase gene. A derived cleaved amplified polymorphic sequence method was developed to detect the ALS mutation in B. syzigachne. This was combined with a previously established method to detect Ile-1781-Leu, and the mutation frequency and homozygous mutation rates in the JCWJ-R population were determined. The evolution of multiple resistance to ACCase and ALS inhibitors in this B. syzigachne population indicated that alternative methods should be developed to control resistant weeds.