Growing populations and intensification of land-use in West Asia and North Africa (WANA) are prompting a need for viable alternatives to fallow and cereal mono-cropping systems common in dry areas of this region. The sustainability and economic viability of such rotations can only be assessed accurately by using long-term trials. A two-course rotation experiment was established in 1986 in north-eastern Syria, comparing yields and profitability of wheat (Triticum aestivum L.) when grown after wheat, fallow, a grazed mixture of medic species (Medicago spp.) and common vetch (Vicia sativa L.) cut for hay, over 10 growing seasons. Lentils (Lens culinaris Medik.) were introduced into the experiment in 1990. On average over the course of the experiment, the highest wheat grain yields were obtained following fallow (2.57 t ha^–1), the lowest in continuous wheat (1.14 t ha^–1), and intermediate following medic and vetch (1.90–2.01 t ha^–1). Compared with wheat grown after fallow, wheat grain yields declined following vetch, medic and lentils in only three of the 10 seasons, which were drier than average. Yields of wheat after lentils were generally lower (2.22 t ha^–1) than after vetch (mean 2.56 t ha^–1) and after medic (2.40 t ha^–1). Inclusion of grain legumes in the rotations boosted profits considerably because of their high grain prices and valuable straw. Replacing fallow with vetch for hay production increased the average gross margin by US$126 ha^–1 year^–1, and growing vetch for hay in rotation with wheat produced greater profit than continuous wheat, by $254 ha^–1 year^–1. The wheat–vetch-for-grain and wheat–lentil rotations were especially profitable, at least twice as profitable as wheat–fallow and three times continuous wheat. This experiment adds to the growing body of field data in Syria and in Australia showing that forage and grain legumes are excellent alternatives to wheat–fallow rotation and continuous wheat production in areas that experience a Mediterranean-type climate, and help support more efficient and sustainable cropping systems.

During the 2007 winter cropping season in Australia, severe leaf-spotting (necrosis) symptoms resembling chloride (Cl^–) deficiency found in North America were reported in the newly released durum wheat variety Jandaroi. Testing for bacterial, fungal and viral pathogens all proved negative. Four Australian durum and four Australian bread wheat varieties were grown, along with a North American variety of each, in a glasshouse experiment using a sterile sand–vermiculite mix and nutrient solutions containing 0 (nil), 0.5, 1.0 or 2.0 mm Cl^–. When grown in the nil Cl^– solution, all durum and some bread wheat varieties produced leaf-spotting symptoms the same as observed in the field. Nil Cl^– also delayed flowering, reduced biomass, decreased grain size, and depressed grain yield in most durum and bread wheat varieties.

In field experiments, additions of Cl^– fertiliser as KCl at sowing provided no biomass or yield response from a range of wheat varieties, probably because the plants accessed sufficient Cl^– from below 0.9 m depth in the soil. Chloride concentrations in whole-plant tissue sampled at head emergence suggested that unfertilised plants were borderline deficient in Cl^– according to critical values established in North America. An in-crop foliar Cl^– application experiment showed linear uptake of applied Cl^–, as MgCl₂, until the end of tillering. However, because leaf-spotting symptoms typically appear only after tillering, it is not possible to correct Cl^– deficiency by adding Cl^– fertiliser to the affected crop after symptoms appear. Managing Cl^– in susceptible crops therefore needs to be preventative rather than curative.

Among commercial varieties, Jandaroi was highly sensitive to low Cl^–, Caparoi was moderately sensitive, and EGA Bellaroi was tolerant. Several elite durum breeding lines grown in 2010 showed considerably reduced leaf spotting compared with Jandaroi under low Cl^– conditions, indicating potential for conventional breeding to reduce the potential impact of low Cl^– soils on durum production in northern Australia.

This study assessed whether more potassium (K) was required for optimal growth and grain yield of cereal crops under drought and salinity than under non-stressed conditions. In 2011, three experiments on wheat (Triticum aestivum L.) with four K rates (0, 20, 40, 80 kg K/ha), four application times (0, 5, 10, 15 weeks after sowing, WAS) and two sources (KCl, K₂SO₄) were conducted in the central and southern grainbelts of Western Australia. The lack of plant response to K supply at the sites of Bolgart (36 mg K/kg at 0–30 cm) and Borden (25 mg K/kg at 0–30 cm), compared with significant gain in K uptake, dry matter and grain yield at Dowerin (29 mg K/kg at 0–30 cm), was not explained by differences in soil K levels. However, rain fell regularly through the growing season at Bolgart and Borden, whereas a dry spell occurred from stem elongation to grain development at Dowerin. The effectiveness of K application time followed the trend of 0, 5 > 10 > 15 WAS. In 2012, barley (Hordeum vulgare L.) was grown on a moderately saline (saturation extract electrical conductivity ∼4 dS/m) and low K (20 mg K/kg) farm in the central grainbelt and treated with 0, 20, 40 and 120 kg K/ha. Applying K increased K uptake but decreased Na uptake, especially at 120 kg K/ha. Plant growth and grain yield increased with K supply, but the difference between the K rates was relatively small, indicating possible partial K substitution by Na. Higher than normal fertiliser K supply on low K soils would enhance the adaptation by cereals to water-limited environments, but K-fertiliser management on moderately saline soils may need to account for both K and Na uptake and use by the crops.

Salinity and high temperature are major abiotic stresses limiting sustainable crop production. Seed priming is a useful tool to enhance seedling growth and the antioxidant defence system of crops under salinity and temperature stress. This experiment was designed to determine the effects of gibberellic acid (GA₃, 288.7 µm), kinetin (232.2 µm) and salicylic acid (362 µm) on some morphological and physiological parameters of sweet sorghum (Sorghum bicolor L. Moench) hybrid Yajin 13 under salinity (0, 100 and 200 mm NaCl) and temperature (25°C and 37°C) stress. Salinity and high temperature significantly reduced emergence percentage, shoot and root lengths, number of leaves, shoot fresh and dry weight, and chlorophyll a and b content. The activity of superoxide dismutase (SOD) and malondialdehyde (MDA) content were increased with an increase in both salinity and temperature stress. Hormone treatments positively affected all parameters except root fresh and dry weight, number of leaves, SOD activity and chlorophyll a. Under salinity stress at 200 mm NaCl, treatment with salicylic acid increased emergence percentage, emergence rate, chlorophyll b and protein content by 82.0%, 130%, 7.9% and 1.9%, respectively, relative to the control (no treatment). At 37°C, salicylic acid increased emergence percentage, emergence rate and number of roots by 72.5%, 108.5% and 63.8%, respectively, and decreased MDA content by 17.6% relative to the control. Our study indicated that seed priming with an appropriate concentration of exogenous hormones (salicylic acid, kinetin, GA₃) is a useful, easy method for improving germination, seedling growth and the antioxidant defence system of sweet sorghum under conditions of high temperature and salinity.

Root penetration and proliferation are directly related to enhanced nutrient and water uptake, and thus to increased crop growth and yield. However, few studies have reported root growth and its seasonal variation in irrigated summer crops in fine-textured soils such as Vertosols. The objective of this study was to quantify the effects of tillage methods and the summer crops cotton (Gossypium hirsutum L.), maize (Zea mays L.) and sorghum (Sorghum bicolor (L.) Moench.) on root density in the non-sodic surface and subsurface soil (0–0.5 m) and sodic subsoil (0.6–0.9 m) of irrigated Vertosols in northern New South Wales (NSW). Root growth of cotton, maize and sorghum was evaluated using a combination of core sampling, and minirhizotrons and an image capture system, in several experiments conducted from 2004 to 2012, near Narrabri, northern NSW. The experimental sites had Vertosol soils with average clay contents of 65 g 100 g^–1 in the surface 1 m, with sodic horizons present at depth. Rooting depth of cotton was relatively shallow, with most roots in the surface 0.6 m. Subsoil (0.6–0.9 m) root growth of cotton was sparse under continuous cotton but was greater with a cotton–wheat rotation. Among cotton genotypes, surface root length density of a Bollgard^® cotton variety was less than that of its non-Bollgard counterpart. Subsoil root growth of sorghum and maize ranged from moderate to high, and accounted for a significant proportion of the total length of their root systems. This may be because maize and sorghum were able to tolerate the waterlogged conditions in the sodic subsoils of these Vertosols.

Chicory (Cichorium intybus L.) and narrow-leaved plantain (Plantago lanceolata L.) are able to grow a large amount of high-quality summer feed. Limited information is available on the effect of grazing management on plantain, and no comparison been undertaken of modern chicory and plantain cultivars used in dairy production systems. This study determined the effect of defoliation interval (as determined by the extended leaf height, ELH) and residual height on the yield, nutritive characteristics and plant density of chicory and plantain over 18 months. Chicory leaf yield was reduced in swards defoliated at 150 mm ELH compared with those defoliated at 250, 350 or 550 mm (14.3 v. 17.5 t DM ha^–1), and chicory stem yield was least in swards defoliated at 150 or 250 mm. Plantain swards defoliated at 350 or 450 mm ELH yielded more leaf than those defoliated at 150 or 250 mm (20.4 v. 16.7 t DM ha^–1); however, stem yield also increased with increasing defoliation interval. Over all seasons, as defoliation interval increased, generally, neutral detergent fibre content increased and crude protein, ash and digestibility declined. Residual height had less of an effect on yield and nutritive characteristics than did defoliation interval. To maximise chicory leaf growth while minimising growth of lower quality stem, the optimal ELH over 18 months was 250 mm, or if the chicory was used only as a 9-month ‘summer’ crop, 350 mm. Recommendations for plantain are not as simple because longer defoliation intervals increase both leaf and stem yield and reduce nutritive value. Defoliating plantain swards at 250 mm ELH appeared to provide a balance between yield and nutritive value; however, further work is required to determine the impact of applying these recommendations on a dairy farm system.

Setaria pumila and Digitaria sanguinalis are undesirable, C₄ annual grass species in intensively managed temperate and subtropical dairy pastures. A comparative, small-plot study was established in Lolium perenne-based dairy pastures to determine the extent to which these species are grazed and how this relates to changes in their nutritive value over summer–early autumn. Setaria pumila was taller than D. sanguinalis before grazing (16–24 and 10–17 cm, respectively) and was grazed to lower post-grazing height and less post-grazing groundcover than D. sanguinalis: height 4.1 and 4.7 cm, cover 67 and 83%, respectively, averaged over January–March (summer–early autumn). Nutritive quality was similar for both species (with metabolisable energy values for December–March averaging 11.1, 10.0, 8.5 and 9.0 MJ kg DM^–1) and is unlikely to be a key determinant of differences in grazing defoliation. In addition, post-grazing cover and post-grazing height for both annual grasses increased over the grazing season and were associated with declining nutritive value of both species. The nutritive value of L. perenne was higher than that of both S. pumila and D. sanguinalis and it did not decline over the grazing season (December–March: 11.3, 11.5, 9.3 and 11.4 MJ kg DM^–1). Although S. pumila and D. sanguinalis were grazed in all months, they readily produced new panicles between grazings. Given this, these annual grasses are likely to spread in Lolium perenne-based dairy pastures unless interventions are used.

Cultivation of legume–grass mixtures ensures a high, protein-rich forage yield with no nitrogen (N) fertilisation. The maintenance of a reasonable proportion of each species over time may depend on the variety. In mixtures of lucerne (Medicago sativa L.) and grass, the effect of genetic variation on biomass and N accumulation is little described. We analysed how lucerne genetic variation affects agronomic traits. The experiment included 46 lucerne and two tall fescue (Festuca arundinacea Schreb.) genotypes tested in microplots of three lucerne and four fescue clones, evaluating biomass production, plant height, stem number and N content in eight cuts in 2011 and 2012. There was a wide genetic variation among lucerne genotypes but no significant statistical interaction between lucerne and fescue genotypes. This suggests that agronomic value of lucerne genotypes for mixtures can be evaluated with any grass genotype. On average, the grass plants grown with highly productive lucerne genotypes had an increased leaf elongation and N status but a reduced tiller number, which could limit their persistence. This is the first observation that the choice of lucerne genotype determines morphology, biomass production and N absorption of both lucerne and tall fescue grown in mixture.

Persistence of pasture is considered an important trait by many farmers using pasture-based systems. Despite this, pasture persistence is generally poorly defined. This study includes an analysis of changes in farm operating profits (OP) when pasture persistence is improved. Persistence was defined as either a 1-year increase in years at peak dry matter (DM) production or a reduction in the rate of decline in annual pasture DM production after the year that peak production occurred (duration of pasture life), both resulting in a 1-year delay in pasture renovation. Changes in OP for these definitions of pasture persistence were modelled for two dairy farms in temperate regions of Australia (Terang in south-western Victoria and Elliott in Tasmania). An increase in duration of peak DM production on the basis of economic theory increased OP more than an increase in duration of pasture life. Increases in OP for a 1-year increase in peak DM production were AU$165 ha^–1 for Terang and $202 ha^–1 for Elliott. This compared with $21 ha^–1 for Terang and $15 ha^–1 for Elliott for a 1-year increase in the duration of pasture life. Therefore, farmers and plant breeders could place more emphasis on improving the duration of time that pasture plants achieve peak DM production than improving pasture persistence at the end of the pasture plant’s lifetime, to increase annual OP.

2,4-Di-tert-butylphenol (2,4-DTBP) is a natural compounds present in medicinal plants. It is reported to have herbicidal properties. However, the mechanism of action is unknown for use in weed management. Measurements were made of lipid peroxidation, ion leakage, antioxidant enzymes, chlorophyll content, chlorophyll fluorescence and photosynthesis in the grassy weed Leptochloa chinensis (L.) Nees and the broadleaf weed Hedyotis verticillata (L.) Lam. at 7 and 14 days, respectively, after treatment with 2,4-DTBP. The 2,4-DTBP reduced the shoot fresh weight of L. chinensis and H. verticillata by 50% when applied at concentrations of 50 and 200 µg mL^–1, respectively. Treatment with 2,4-DTBP significantly increased levels of malondialdehyde, caused excessive ion leakage and increased activities of antioxidant enzymes such as superoxide dismutase, peroxidase and catalase in leaf and root tissues of the two bioassay species. Most notably, 2,4-DTBP treatment caused great reduction in chlorophyll content, thereby decreasing chlorophyll fluorescence, transpiration and net photosynthetic rate in the leaf tissues. The results suggest that 2,4-DTBP induces oxidative stress through the generation of reactive oxygen species, which cause lipid peroxidation and membrane damage in root tissues and chloroplast in leaf tissues, thus leading to increased levels of antioxidant enzymes.

A 2-year study was conducted to examine the impact of deficit irrigation on dry biomass, water-use efficiency (WUE), fruit yield and quality in open-field processing tomato at high plant density in a semi-arid environment. Three irrigation treatments (nil; and 100% (full) and 50% (deficit) restoration of crop evapotranspiration (ETc), respectively) and two plant densities (2.5 (P1) and 5.0 (P2) plants m^–2) were studied. Dry biomass and fruit yield per plant were lower in P2 than in P1, but at high plant density the crop compensated for biomass and yield decrease at the plant level. Fruit yield in P2 was greater than that in P1, by 36% in 2004 and 33% in 2005. Water limitation improved quality traits compared with full irrigation. Deficit irrigation, especially in P2, enhanced WUE and allowed a water saving of >45% relative to full irrigation, while keeping high levels of fruit quality. The yield response factor, Ky, which correlates relative fruit yield losses to relative ETc reduction, was higher (0.63) than Kss (0.44), which correlates relative total dry biomass losses to relative ETc reduction, revealing a greater crop sensitivity to soil-water deficit in terms of fruit yield than dry biomass. Therefore, Ky may of use in identifying the plant density at which water productivity is maximised or yield losses are minimised.