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Extreme weather (high rainfall and temperatures) and challenging soils are sources of uncertainties in the use of current crop models that have been developed for more favorable environments. This may limit their applicability to guide and support decision making for the development of new agricultural regions in tropical environments. We evaluated the accuracy of the Agricultural Production Systems Simulator (APSIM) framework in representing yield and development of a range of crops across multiple locations in the Northern Territory of Australia, a tropical region with large potential for agricultural development. Observations of yield, biomass, and phenology for a range of crops from 28 experiments undertaken at three locations were compiled and used to develop simulations undertaken using APSIM version 7.10. Model performance varied with coefficients of determination and concordance correlation coefficients ranging from 0.36 to 0.98 and 0.37 to 0.93, respectively. Instances where model performance was less than ideal were associated with conditions presenting a limited number of observed values. Deviations by the model from yield observations were larger for situations with high‐yielding crops and low daily maximum temperatures during vegetative growth stages. Deviations in phenology were larger for conditions associated with water and N stress. APSIM was capable of representing the yield, biomass, and development of cereal and pulse crops and can be used with confidence to assist the expansion of agriculture in tropical environments such as the Northern Territory of Australia. Core Ideas: The accuracy of crop models for environments frequented by challenging weather and soils is rarely reported.We showed that the Agricultural Production Systems Simulator (APSIM) performs well in one such environment, the Northern Territory of Australia.APSIM can be used with confidence in environments with challenging weather and soil conditions. [ABSTRACT FROM AUTHOR]

Simple Summary: We observed a forage allowance by forage type effect on improvements in the daily milk yield of dairy cows grazing swards sown with perennial ryegrass, white clover and plantain relative to those sown to perennial ryegrass only. Improvements in milk yield were evident at lower forage allowances of 14 to 20 kg of dry matter/cow per day (inclusive), diminishing at the highest allowance of 25 kg of dry matter/cow per day. At the lower forage allowances, energy intake would have been a limiting factor for milk production, potentially highlighting the nutritive advantages of plantain and white clover. Increasing species diversity is a possible strategy for overcoming seasonal nutritive challenges present in perennial ryegrass monocultures. We tested for a forage allowance effect on the milk yield of early lactation dairy cow herds grazing swards sown with perennial ryegrass (Lolium perenne L.), white clover (Trifolium repens L.) and plantain (Plantago lanceolata L.) relative to perennial ryegrass alone. The examined allowances consisted of offering 12, 14, 16, 18, 20 or 25 kg of dry matter (DM)/cow per day of grazeable herbage, with diverse swards sown as mixtures and spatially adjacent monocultures. After adapting cows to their assigned forage type for 8 days, treatment effects on milk yield and composition, blood metabolites (beta-hydroxybutyrate, non-esterified fatty acids and urea concentrations), body weight change, forage intake and selection differentials for forage species and certain nutrients were monitored over 7 days. We confirmed a forage allowance effect on milk yield improvements in dairy cows grazing diverse swards relative to perennial ryegrass monocultures. Improvements in milk yield were evident at forage allowances of 14 to 20 kg of DM/cow per day, diminishing at the highest allowance of 25 kg of DM/cow per day. Improvements in milk yield for the mixture and spatially adjacent monocultures peaked at forage allowances of 18 and 16 kg of DM/cow per day, equalling increases of 1.3 and 1.2 kg of milk/cow per day, respectively. [ABSTRACT FROM AUTHOR]

Exploring improved tropical forages is considered to be an important approach in delivering quality and consistent feed options for dairy cattle in tropical and subtropical regions. The present study aimed to study the suitability of three improved tropical grasses, Chloris gayana 'Rhodes grass cv. Reclaimer' (RR), Megathyrsus maximus 'Gatton Panic' (GP), and Brachiaria ruziziensis x B. decumbens x B. brizantha 'Brachiaria Mulato II' (BM) evaluating their carbon assimilation, canopy structure, herbage plant–part accumulation and quality parameters under irrigated conditions. An experiment was conducted at Gatton Research Dairy (27°54′ S, 152°33′ E, 89 m asl) Queensland, Australia, which has a predominantly subtropical climate. Photosynthesis biochemistry, canopy structure, herbage accumulation, plant part composition, and nutritive value were evaluated. Photosynthesis biochemistry differed between pasture species. Efficiency of CO2 assimilation was highest for GP and quantum efficiency was highest for BM. Pasture canopy structure was significantly affected by an interaction between pasture species and harvest. Forage biomass accumulation was highest in GP, while BM produced more leaf and less stem compared to both GP and RR. A greater leafy stratum and lower stemmy stratum depth were observed in the vertical sward structure of BM. Brachiaria Mulato II showed greater carbon partitioning to leaves, leaf: stem ratio, canopy, and leaf bulk density. It also demonstrated greater nutritive value (Total digestible nutrients (TDN), acid detergent fibre (ADF), neutral detergent fibre (NDF), neutral detergent insoluble protein (NDICP), Starch, nonfibre carbohydrates (NFC), metabolisable energy (ME), mineral profile (Mg, P, K, Fe, Zn) and dietary cation–anion difference (DCAD) for leaf, stem, and the whole plant. Greater quantum efficiency, leaf accumulation, and nutritive value of BM observed in the present study suggest BM as an attractive forage option for dairying that warrants further research in pasture-based systems in tropical and subtropical climates. [ABSTRACT FROM AUTHOR]

Growth of alfalfa (Medicago sativa L.) following the correction of water deficits will depend, in part, on the amount of plant constituents available to support regrowth and the availability of crown buds for the development of new shoots. To investigate if water deficit affected the accumulation of taproot constituents and crown bud development of alfalfa, two alfalfa cultivars were exposed to increasing levels of water deficit (100, 75, 50 25 and 0% of the replacement water requirement) during a regrowth period. Shoot growth was reduced in proportion to the level of water deficit. Taproot starch concentrations decreased while taproot soluble sugar increased in plants exposed to a water deficit. Thirty-five d after initiation of treatments, taproot protein and amino acid concentrations were similar in all treatments that received water. Water deficit increased the relative concentration of low and middle molecular weight taproot vegetative storage proteins (VSP) and water deficits reduced the number and mass of green crown buds. Both cultivars had a similar response to water deficit for all taproot constituents and crown bud development. Further studies are required to determine the influence of increasing VSP abundance and decreasing numbers of crown buds on plant recovery following the removal of a water deficit. doi: 10.2135/cropsci2009.03.0140

Growth of alfalfa (Medicago sativa L.) following the correction of a water deficit will depend in part on the characteristics of the canopy grown during the water deficit. The current study was undertaken to determine the extent to which canopy structure and photosynthetic capacity are affected in alfalfa plants regrowing following defoliation while exposed to a water deficit. The effects of five levels of water application (100, 75, 50, 25, and 0% of the replacement water requirement) during the regrowth of two alfalfa cultivars with contrasting levels of fall dormancy was investigated in a controlled environment. Mass per shoot and shoots per plant were both significantly (P < 0.05) reduced by water applications 75% or less of the replacement water requirement. Dry matter accumulation was reduced in proportion to the level of the water deficit the plants were exposed to. The rate of C[O.sub.2]assimilation and maximum efficiency of photosystem II were unaffected (P > 0.05) by water deficits except for the unwatered plants on which leaf senescence occurred. The only inhibition in the plants' capacity for photosynthesis from a water deficit was reduced leaf area. Shoot density and reduced overall canopy photosynthesis were the only canopy characteristics that were altered by water deficit in a way that could continue to inhibit plant growth following the correction of the water deficit.

Simple Summary: Globally, tropical pasture species predominate in tropical and subtropical climates, and are the primary feed source for grazing livestock including dairy cattle. Therefore, this study aimed at systematically analysing the nutritive values of tropical pastures and the implications of potential methane gas production from tropical pasture species and livestock, in relation to the growing conditions and agronomic management approaches used (defoliation frequency and intensity) across different climates. This analysis allowed us to understand the better performing tropical pasture species grown across wider geographical regions, in order to improve pasture-based livestock production systems. Results revealed that pasture quality and methane gas production varied among and within species, and were significantly affected by the climate and by the agronomic management regime as well. The demand for dairy products is ever increasing across the world. The livestock sector is a significant source of greenhouse gas (GHG) emissions globally. The availability of high-quality pasture is a key requirement to increase the productivity of dairy cows as well as manage enteric methane emissions. Warm-season perennial grasses are the dominant forages in tropical and subtropical regions, and thus exploring their nutritive characteristics is imperative in the effort to improve dairy productivity. Therefore, we have collated a database containing a total of 4750 records, with 1277 measurements of nutritive values representing 56 tropical pasture species and hybrid cultivars grown in 26 different locations in 16 countries; this was done in order to compare the nutritive values and GHG production across different forage species, climatic zones, and defoliation management regimes. Average edaphoclimatic (with minimum and maximum values) conditions for tropical pasture species growing environments were characterized as 22.5 °C temperature (range 17.5–29.30 °C), 1253.9 mm rainfall (range 104.5–3390.0 mm), 582.6 m elevation (range 15–2393 m), and a soil pH of 5.6 (range 4.6–7.0). The data revealed spatial variability in nutritive metrics across bioclimatic zones and between and within species. The ranges of these nutrients were as follows: neutral detergent fibre (NDF) 50.9–79.8%, acid detergent fibre (ADF) 24.7–57.4%, crude protein (CP) 2.1–21.1%, dry matter (DM) digestibility 30.2–70.1%, metabolisable energy (ME)3.4–9.7 MJ kg−1 DM, with methane (CH4) production at 132.9–133.3 g animal−1 day−1. The arid/dry zone recorded the highest DM yield, with decreased CP and high fibre components and minerals. Furthermore, the data revealed that climate, defoliation frequency and intensity, in addition to their interactions, have a significant effect on tropical pasture nutritive values and CH4 production. Overall, hybrid and newer tropical cultivars performed well across different climates, with small variations in herbage quality. The current study revealed important factors that affect pasture nutritive values and CH4 emissions, with the potential for improving tropical forage through the selection and management of pasture species. [ABSTRACT FROM AUTHOR]

Prospects for improving the productivity of species mixtures in transitions between phases by changing row configuration at sowing were examined in two series of field experiments in rain-fed, semi-arid environments in south-eastern Australia. The first series explored how the choice of cover crop and use of alternate drill row configurations affected establishment and yields of sward components in the transition from a cropping into a pasture phase. Cover-crop species included wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), c anola (Brassica napus L.) a nd l upins (Lupinus augustifolius L.), e ach s own i n m ixed o r a lternate d rill r ows w ith l ucerne (Medicago sativa L.) and subterranean clover (Trifolium subterraneum L.). The second series of experiments examined the productivity implications when returning from the pasture phase back into cropping following 10 contrasting pastures sown to various combinations of lucerne, subterranean clover or phalaris (Phalaris aquatica L.) sown in mixed, alternate (1:1) or double skip (1:2) row configurations in the absence of cover crops. All experiments were sown on a 0.25-m row spacing. In the transition into the pasture phase, grain yields of cover crops in the mixed drill row treatment were similar to those achieved by crops grown in the absence of pasture species but were reduced by an average of 24% in the alternate drill row configuration. Canola and lupin crop biomass were lower, compared with wheat and barley, leading to increased pasture yields in year 1, highlighting an opportunity for increased use of these species as cover/companion crops in semi-arid environments. Pasture yields beyond year 1 were reduced by ~20% in the alternate drill row treatments compared with where species were sown in mixed drill rows, with greater yield differences under more favourable growing conditions. This response largely reflected yield reductions in lucerne where it was concentrated in fewer drill rows. The alternate drill row configuration increased the abundance of subterranean clover in year 1, but this species remained a minor component of all swards beyond the establishment year. In the transition into the cropping phase, effects on grain quality could only be attributed to row configuration of the previous pasture to the extent that row configuration changed pasture composition. Grain size was smallest and protein concentration highest where previous pastures contained both lucerne and subterranean clover without phalaris. Taken together, there was little advantage in total productivity attributable to spatially separating species in drill rows at sowing. [ABSTRACT FROM AUTHOR]

Spatial separation of species at sowing has been proposed as a means of managing interspecific competition in mixed swards. This study examined the effect of row configuration on persistence of lucerne (Medicago sativa L.) in pastures and pasture–cover crop mixtures at three sites in the Central West, and in pasture mixtures at three sites in the Riverina, New South Wales, Australia. Lucerne density, taproot diameter, groundcover, and spatial distribution relative to the original drill row were measured at all sites, and plant-available soil water and light interception during spring were assessed at some sites. Row configuration (alternate or mixed drill rows) did not affect lucerne persistence; however, where lucerne seed was concentrated in every third drill row, intraspecific competition led to increased lucerne mortality. This was estimated to occur at densities >28 plants/m drill row. A lucerne density of ~55 plants/m2 in every or alternate drill rows (at row spacings of 250 mm) would likely achieve maximum lucerne production in the semi-arid environments tested, subject to the chance event of favourable conditions in the period after sowing that would maintain that density (e.g. cumulative summer rainfall >100 mm and summer day degrees <2160°C in 2 years at Cowra). The presence of a cover crop in the establishment year reduced lucerne density by 39% compared with pasture only, regardless of row configuration. Changed row configuration did not reduce competition for light under a cover crop, but there was a small increase in available soil water of up to 4.9 mm in the 0–1.15 m depth, mainly during the first summer, where pasture was sown in alternate compared with mixed drill rows with a cover crop. Soil was drier in pasture-only treatments than those with a cover crop, attributable to increased lucerne density and lower levels of litter cover on the soil surface. Pasture species remained largely confined to the original drill row, especially in drier environments, highlighting the importance of narrower row spacings for pasture establishment. In addition, we determined a mathematical relationship between lucerne density and the non-destructive measure of basal frequency; this relationship could be applied in mature lucerne stands with densities ≤80 plants/m2. This study examined whether separating species in drill rows at sowing improved lucerne survival over a short pasture phase compared with multiple species being sown in the same row. Persistence was reduced only where lucerne was confined to every third drill row, indicating the effect of intraspecific competition on lucerne density; furthermore, interspecific competition from cover crops in the first year consistently reduced lucerne density. The study highlights the importance of narrower rather than wider row spacings in drier environments where pastures remained concentrated around the drill row, and shows that winter-active forage species are important for improving productivity of lucerne-based swards. [ABSTRACT FROM AUTHOR]

Changed spatial configurations at sowing have been investigated as a strategy to minimize interspecific competition and improve the establishment and persistence of multi-species plantings in pastures, but the impact of this practice on the soil microbiome has received almost no previous research attention. Differences in populations of bacteria and fungi in the surface 10 cm of soil in the third year following pasture establishment were quantified using quantitative polymerase chain reaction and terminal restriction fragment length polymorphism methods. Populations were compared on, and between, drill rows sown to either the perennial grass phalaris (Phalaris aquatica L.), perennial legume lucerne (alfalfa; Medicago sativa L.) or the annual legume subterranean clover (Trifolium subterraneum L.). Results showed that soil microbial abundance and diversity were related to plant distribution across the field at the time of sampling and to soil chemical parameters including total carbon (C), mineral nitrogen (N), pH, and available phosphorus (P), potassium (K) and sulfur (S). Despite the 27-month lag since sowing, pasture species remained concentrated around the original drill row with very little colonization of the inter-row area. The abundance and diversity of bacterial and fungal populations were consistently greater under drill rows associated with higher total C concentrations in the surface soil compared with the inter-row areas. Our results showed that the pH and available nutrients were similar between the subterranean clover drill row and the inter-row, suggesting that soil microbial populations were not impacted directly by these soil fertility parameters, but rather were related to the presence or absence of plants. The abundance of bacteria and fungi were numerically lower under phalaris rows compared to rows sown to legumes. The richness and diversity of fungal populations were lowest between rows where lucerne was planted. Possible explanations for this observation include a lower C:N ratio of lucerne roots and/or a lack of fibrous roots at the soil surface compared to the other species, illustrating the influence of contrasting plant types on the soil microflora community. This study highlights the enduring legacy of the drill row on the spatial distribution of plants well into the pasture phase of a cropping rotation and discusses the opportunity to enhance the microbiome of cropping soils on a large scale during the pasture phase by increasing plant distribution across the landscape. [ABSTRACT FROM AUTHOR]

Forage management underpins the viability of pastoral dairy systems. This review investigated recent developments in forage research and their potential to enable pastoral dairy systems to meet the challenges that will be faced over the next 10 years. Grazing management, complementary forages, pasture diversity, fertiliser use, chemical restriction, irrigation management and pasture breeding are considered. None of these areas of research are looking to increase production directly through increased inputs, but, rather, they aim to lift maximum potential production, defend against production decline or improve the efficiency of the resource base and inputs. Technology approaches consistently focus on improving efficiency, while genetic improvement or the use of complementary forages and species diversity aim to lift production. These approaches do not require additional labour to implement, but many will require an increase in skill level. Only a few areas will help address animal welfare (e.g. the use of selected complementary forages and novel endophytes) and only complementary forages will help address increased competition from non-dairy alternatives, by positively influencing the properties of milk. Overall, the diversity of activity and potential effects will provide managers of pastoral dairy systems with the best tools to respond to the production and environmental challenges they face over the next 10 years. Forage management underpins the success of pastoral dairy industries. Recent dairy forage research was reviewed through a production and input loss frontier framework along with their potential impacts on competition from non-dairy alternatives, labour and animal welfare challenges. The diversity of approaches to modifying both the production and input loss frontiers will provide the tools for pasture managers to meet future production and environmental challenges. [ABSTRACT FROM AUTHOR]

The profitability of dairying in south-eastern Australia can be improved by increasing pasture production during summer–autumn, when growth rates for the existing perennial ryegrass (Lolium perenne L.) feedbase are low. A study undertaken in cool-temperate north-west Tasmania examined the effect of stubble height and irrigation management on swards of perennial ryegrass, continental (summer-active) tall fescue (Festuca arundinacea Schreb.) and chicory (Cichorium intybus L.). Irrigation treatments included full irrigation (~20 mm applied at every 20 mm precipitation deficit), deficit irrigation (~20 mm applied at alternate full-irrigation events) and rainfed (no irrigation). All species achieved greater summer–autumn yields when repeatedly defoliated to stubble heights of 35 or 55 mm than when defoliated to 115 mm, irrespective of irrigation treatment. Swards were managed under a common defoliation schedule of nine defoliation events in 12 months. Under full irrigation, second-year tall fescue achieved a greater summer–autumn yield than perennial ryegrass (by 10%, or 0.7 t DM ha–1), highlighting the potential role of tall fescue in north-west Tasmania. This was further demonstrated by the high marginal irrigation water-use index values (1.6–2.7 t DM ML–1) of tall fescue. By contrast, summer–autumn growth achieved by chicory was less than or equal to perennial ryegrass. The profitability of dairying in south-eastern Australia can be improved by increasing summer–autumn pasture production. In a study in cool-temperate north-west Tasmania, perennial ryegrass, tall fescue and chicory achieved higher summer–autumn yields when repeatedly defoliated to stubble heights of 35 or 55 mm cf. 115 mm. When regularly irrigated to correct precipitation deficits, tall fescue showed potential to increase summer-autumn yields beyond that of perennial ryegrass. [ABSTRACT FROM AUTHOR]

Defoliating pasture to shorter stubble heights (height above the soil surface) may increase temperature at the plant crown (plant–soil interface). This is especially relevant to summer C3 pasture production in parts of south-eastern Australia, where above-optimal ambient temperatures (≥30°C) are often recorded. A rainfed field experiment in north-west Tasmania, Australia, quantified the effect of stubble-height management on the upper distribution of crown temperatures (90th and 75th percentiles) experienced by three pasture species: perennial ryegrass (Lolium perenne L.), tall fescue (Festuca arundinacea Schreb.; syn. Schedonorus arundinaceus (Schreb.) Dumort.; syn. L. arundinaceum (Schreb.) Darbysh.), and chicory (Cichorium intybus L.). Three stubble-height treatment levels were evaluated: 35, 55 and 115 mm. Defoliation to shorter stubble heights (35 or 55 mm cf. 115 mm) increased the crown temperature of all species in the subsequent regrowth cycle (period between successive defoliation events). In the second summer, defoliating to shorter stubble heights increased the 90th percentile of crown temperature by an average of 4.2°C for perennial ryegrass, 3.6°C for tall fescue and 1.8°C for chicory. Chicory and second-year tall fescue swards experienced less-extreme crown temperatures than perennial ryegrass. This may partly explain why these two species often outyield perennial ryegrass in hotter summer environments than north-west Tasmania, and hence the increasing interest in their use. Above-optimal ambient temperatures (≥30°C) challenge summer pasture production in south-eastern Australia. A field experiment showed that defoliating to shorter stubble heights (35 or 55 mm cf. 115 mm) contributed to elevating the crown temperature of three pasture species, which may have negative implications for plant growth and survival during hot summers. Chicory and second-year tall fescue experienced less-extreme crown temperatures than perennial ryegrass, which may partly contribute to the superior growth of chicory and tall fescue in hot summer environments. [ABSTRACT FROM AUTHOR]

In many south-eastern Australian dairying regions, supraoptimal ambient temperatures (Ta > 30°C) often challenge the perennial ryegrass (Lolium perenne L.)-dominated feed-base during the summer months. A glasshouse experiment was undertaken to identify alternative summer-active temperate (C3) perennial forages more tolerant of supraoptimal temperature stress (day/night Ta of 38/25°C) than perennial ryegrass. Supraoptimal temperature stress was mposed both with and without irrigation. Chicory (Cichorium intybus L.) was the only species to survive 18 days of combined supraoptimal temperature stress and non-irrigation. Lucerne (Medicago sativa L.), plantain (Plantago lanceolata L.), and tall fescue (Festuca arundinacea Schreb.) survived 12 days of this treatment. Twelve days of exposure to these conditions caused death of perennial ryegrass, prairie grass (Bromus catharticus Vahl.), cocksfoot (Dactylis glomerata L.), birdsfoot trefoil (Lotus corniculatus L.), and red clover (Trifolium pratense L.). Irrigation (daily to through drainage) mitigated detrimental effects of imposed supraoptimal temperature stress on the growth and survival of all species. Chicory and to a lesser extent lucerne, plantain, and tall fescue may have a role to play in south-eastern Australian dairying regions, where supraoptimal temperature stress is a frequent and ongoing issue. [ABSTRACT FROM AUTHOR]

Several models exist to predict lucerne (Medicago sativa L.) dry matter production; however, most do not adequately represent the ecophysiology of the species to predict daily growth rates across the range of environments in which it is grown. Since it was developed in the late 1990s, the GRAZPLAN pasture growth model has not been updated to reflect modern genotypes and has not been widely validated across the range of climates and farming systems in which lucerne is grown in modern times. Therefore, the capacity of GRAZPLAN to predict lucerne growth and development was assessed. This was done by re-estimating values for some key parameters based on information in the scientific literature. The improved GRAZPLAN model was also assessed for its capacity to reflect differences in the growth and physiology of lucerne genotypes with different winter activity. Modifications were made to GRAZPLAN to improve its capacity to reflect changes in phenology due to environmental triggers such as short photoperiods, declining low temperatures, defoliation and water stress. Changes were also made to the parameter governing the effect of vapour pressure on the biomass-transpiration ratio and therefore biomass accumulation. Other developments included the representation of root development and partitioning of canopy structure, notably the ratio leaf : stem dry matter. Data from replicated field experiments across Australia were identified for model validation. These data were broadly representative of the range of climate zones, soil types and farming systems in which lucerne is used for livestock grazing. Validation of predicted lucerne growth rates was comprehensive owing to plentiful data. Across a range of climate zones, soils and farming systems, there was an overall improvement in the capacity to simulate pasture dry matter production, with a reduction in the mean prediction error of 0.33 and the root-mean-square deviation of 9.6 kg/ha.day. Validation of other parts of the model was restricted because information relating to plant roots, soil water, plant morphology and phenology was limited. This study has highlighted the predictive power, versatility and robust nature of GRAZPLAN to predict the growth, development and nutritive value of perennial species such as lucerne. [ABSTRACT FROM AUTHOR]

For Australian and New Zealand dairy farms, the primary source of home-grown feed comes from grazed perennial pastures. The high utilisation of perennial pasture is a key factor in the low cost of production of Australian and New Zealand dairy systems and, hence, in their ability to maintain international competiveness. The major pasture species used are perennial ryegrass (Lolium perenne L.) and white clover (Trifolium repens L.), normally grown in a simple binary mixture. As pasture production has been further driven by increasing use of nitrogen fertiliser and irrigation, farms are getting closer to their economic optimum level of pasture utilisation. Increasing inputs and intensification have also increased scrutiny on the environmental footprint of dairy production. Increasing the diversity of pasture species within dairy swards presents opportunities to further increase pasture utilisation through additional forage production, extending the growing season, improving forage nutritive characteristics and, ultimately, increasing milk production per cow and/or per hectare. Diverse pastures also present an opportunity to mitigate some of the environmental consequences associated with intensive pasture-based dairy systems. A consistent finding of experiments investigating diverse pastures is that their benefits are due to the attributes of the additional species, rather than increasing the number of species per se. Therefore, the species that are best suited for inclusion into dairy pastures will be situation specific. Furthermore, the presence of additional species will generally require modification to the management of dairy pastures, particularly around nitrogen fertiliser and grazing, to ensure that the additional species remain productive and persistent. Diverse pastures offer benefits to pasture-based dairy systems in terms of increased forage and animal production, improved resilience and the potential to reduce nitrate leaching. The management required to maintain the diversity in the pastures may limit their application. However, the benefits of diverse pastures can be archived with only three species making their management and application simpler. [ABSTRACT FROM AUTHOR]

Abstract: Considerable variability in the yield response of temperate dairy pastures to the strategic use of nitrogen (N) fertiliser has been observed previously. Some of this variation could potentially be attributed to environmental effects on the available N (soil mineral N plus fertiliser N) concentration required to optimise pasture growth. Five nitrogen application rate response field experiments were undertaken in an attempt to elucidate the environmental influence on pasture mineral N requirements. A significant response to N fertiliser application rate was detected in four out of the five experiments. The absence of a significant response in one experiment can be attributed to limited water availability. Across the experiments where a significant response to N fertiliser rate was detected the available N that was required to achieve 90% of maximum yield ranged between 60 and 81kgN/ha. It is concluded that when water availability, soil temperatures and air temperatures are conducive to pasture growth an available N level of between 60 and 81kgN/ha should be targeted when N fertiliser is used strategically to optimise pasture growth. Soil N testing results should be interpreted in light of the prevailing climatic and edaphic conditions if they are to be used to guide N fertiliser rate decisions within intensively managed temperate pastures. [Copyright &y& Elsevier]

Irrigated cotton (Gossypium hirsutum L.) growers in the Murray-Darling Basin (MDB) of Australia, are challenged by limited water availability. This modelling-study aimed to determine if deficit irrigation (DI) practices can potentially improve water use efficiency (WUE) for furrow irrigation (FI), overhead sprinkler irrigation (OSI) and subsurface drip irrigation (SDI) systems. We validated the Agricultural Production System sIMulator (APSIM) against observed cotton lint yield and crop biomass accumulation for different management practices. The model achieved concordance correlation coefficients of 0.93 and 0.82 against observed cotton crop biomass accumulation and lint yields, respectively. The model was then applied to evaluate the impacts of different levels of DI on lint yield, WUE across cotton growing locations in the MDB (Goondiwindi, Moree, Narrabri, and Warren), during the period from 1977 to 2017. The different levels of DI for the FI system were no irrigation, full irrigation (TF) and irrigated one out of four, one out of three, one out of two, two out of three and two out of four TF events. For the OSI and SDI systems, DI levels were no irrigation, TF, 20% of TF, 40% of TF, 60% of TF and 80% of TF. Lint yield was maximised under the OSI and SDI systems for most locations by applying 80% of TF. However; modelling identified that WUE was maximised at 60% of full irrigation for OSI and SDI systems. These results suggest there are significant gains in agronomic performance to be gained through the application of DI practices with these systems. For FI, DI had no benefit in terms of increasing yield, while DI showed marginal gains in terms of WUE in some situations. This result is due to the greater exposure to periodic water deficit stress that occurred when DI practices were applied by an FI system. The results suggest that in the northern MDB, water savings could be realised for cotton production under both OSI and SDI systems if DI were adopted to a limited extent, depending on location and irrigation system. [ABSTRACT FROM AUTHOR]

Forage brassicas have historically been used in high rainfall/irrigated temperate livestock systems, but there is increasing interest in diverse forage brassicas in drier mixed crop-livestock farming systems. Computer-based modelling is an important decision support tool used in agriculture to explore the adaptability of crops to different climates and agronomic management practices, but existing modelling tools for forage brassicas are limited to temperate environments. We parameterised the APSIM (Agricultural Production Systems Simulator) model for four forage brassica genotypes, including three diverse forage rape cultivars and a raphanobrassica. The model was calibrated using two experiments with repeated measures of biomass components, nutritive value, and leaf and canopy development. We then tested the model extensively using data from a diverse set of environments within Australian and New Zealand (23 sites across four agro-climatic zones). Model predictions of biomass were good for all the genotypes (NSE > 0.60, Nash-Sutcliffe efficiency; RMSE ~1.5 t DM/ha, root mean square error). Predictions of metabolisable energy yield were satisfactory for all genotypes (NSE 0.43–0.73; RMSE ~17.8 GJ ME/ha) but forage dry matter digestibility (DMD) were poorly predicted due to the small variation in observed data. Our robust and widely tested model can be confidently used to predict forage productivity of common and new forage brassicas across a wide range of production environments and agronomic management practices. This model will enable future work to develop a better understanding of the potential value of these important forage crops for livestock production systems. • A forage brassica model, including three diverse forage rape cultivars and a raphanobrassica were parameterised in APSIM. • Forage brassica productivity during vegetative growth can be modelled in different environments and agronomic practices. • These new capabilities enable the value of forage brassicas to farming systems to be explored in different environments. [ABSTRACT FROM AUTHOR]