Andrew D. Moore

GRAZPLAN: Decision support systems for Australian grazing enterprises—II. The animal biology model for feed intake, production and reproduction and the GrazFeed DSS

Abstract This paper specifies the animal biology module of a model for simulating grazing systems for ruminants on pasture. The program predicts the intake of energy and protein, allowing for selective grazing and substitution by supplementary feeds, and estimates the use of the diet for maintenance and production, according to current feeding standards. Conception and death rates are predicted from the maturity and condition of the animals. The model is designed to be of general application to any type of sheep or cattle on any pasture. GrazFeed is a discrete package that uses the same procedures for predicting feed intake and productivity within a tactical decision support system. This is designed to help graziers to assess the feeding value of specified pastures and the need for the supplementary feeding of different classes of grazing animals.

GRAZPLAN: Decision support systems for Australian grazing enterprises. III. Pasture growth and soil moisture submodels, and the GrassGro DSS

This paper specifies the pasture growth module of a model for simulating grazing systems for ruminants and the soil moisture budget that drives pasture growth. Both modules operate at a daily time step. The pasture growth module is quite general in structure but recognises four functional groups of pasture plants: annual and perennial species are distinguished, as are grasses and forbs. Shoot tissue is classified as live, senescing, standing dead, or litter, and also according to its dry matter digestibility, thus enabling integration with diet selection and feed intake models. The phenological development of pasture plants is modelled, with the transitions between each stage governed by environmental variables (day length, temperature and soil moisture). Prereproductive and postreproductive phenostages of vernalisation and ‘summer dormancy’, respectively, are modelled in the appropriate cultivars. Functions predicting net primary production in response to light intercepted, mean daytime temperature, and available soil moisture, and also the process of maturation, are common to all functional groups. The models treatment of the allocation of assimilate has a similarly general form. Seed and seedling dynamics are modelled for annual species only. GrassGro is a discrete computer package, developed for Microsoft Windows,™ that combines the pasture growth module with a module for predicting the intake of herbage of ruminants and their productivity. This decision support system enables users to analyse simplified grazing systems in terms of pasture and animal production, gross margins, and year-to-year variability for any specified pasture cultivar, or combination of cultivars, at any specified site. The package may also be used to simulate forward from current pasture and animal conditions, for assessing the probability distribution of production outcomes, given the historical variability of weather conditions over the specified forward period.

Morphology and response of roots of pasture species to phosphorus and nitrogen nutrition

The root morphology of ten temperate pasture species (four annual grasses, four perennial grasses and two annual dicots) was compared and their responses to P and N deficiency were characterised. Root morphologies differed markedly; some species had relatively fine and extensive root systems (Vulpia spp., Holcus lanatus L. and Lolium rigidum Gaudin), whilst others had relatively thick and small root systems (Trifolium subterraneum L. and Phalarisaquatica L.). Most species increased the proportion of dry matter allocated to the root system at low P and N, compared with that at optimal nutrient supply. Most species also decreased root diameter and increased specific root length in response to P deficiency. Only some of the species responded to N deficiency in this way. Root morphology was important for the acquisition of P, a nutrient for which supply to the plant depends on root exploration of soil and on diffusion to the root surface. Species with fine, extensive root systems had low external P requirements for maximum growth and those with thick, small root systems generally had high external P requirements. These intrinsic root characteristics were more important determinants of P requirement than changes in root morphology in response to P deficiency. Species with different N requirements could not be distinguished clearly by their root morphological attributes or their response to N deficiency, presumably because mass flow is relatively more important for N supply to roots in soil.

GRAZPLAN: Decision support systems for Australian grazing enterprises--I. Overview of the GRAZPLAN project, and a description of the MetAccess and LambAlive DSS

Abstract Effective transfer of new information and technology to farming practice is the major goal of the GRAZPLAN project. GRAZPLAN contains a suite of complementary decision support systems (DSS) that incorporate results from research on grazing systems and are now being released through a commercial partner as aids to extension. These computer packages are designed to be used in conjunction with local weather and farm data to test the relevance of different management procedures for individual farms. The main DSS, GrazPlan, can be used to evaluate and optimize long-term management decisions in relation to profitability and sustainability. It is quite general in its application and modular in structure. The Australia-wide database of daily weather records, which drives this program, is the basis for two smaller DSS, MetAccess and LambAlive, which are described in this paper. MetAccess is designed to display and analyse daily weather records and provide users with estimates of the probability of specified weather patterns within the range of data from a specified locality. LambAlive is designed to predict the risk of lamb deaths from bad weather for specified localities and flocks and enables the user to test different procedures that may reduce these losses.

Evolution of the GRAZPLAN decision support tools and adoption by the grazing industry in temperate Australia

Abstract CSIRO Plant Industry has developed the GRAZPLAN family of decision support tools (DS tools) for consultants and farmers to improve the profitability and environmental sustainability of grazing enterprises. These tools are based on pasture and animal production models that have general application for simulating the biophysical processes of grazing systems in temperate southern Australia. The DS tools are designed to be easy to use and, apart from daily weather information, require minimal input of data. Where relevant, the models run continuously over a range of specified years, without further intervention by the user. The output generated can be linked to cost and price indices to enable estimation of production risk in financial as well as in biological terms. Adoption of GrazFeed, a tool to guide livestock nutrition, is widespread in the southern states where it is a keystone for the very successful PROGRAZE extension program sponsored by NSW Agriculture and Meat and Livestock Australia. GrazFeeds success is linked to the release of national feeding standards for ruminants, to the tactical nature of decisions about livestock nutrition and to a formal commitment by CSIRO, the developers, with NSW Agriculture, a major user. Adoption of another tool, GrassGro, which is used to analyse grazing enterprises for profit and sustainability, is slower. In this case the decision support is concerned with strategic planning where outcomes are probability-based and where the pasture model in GrassGro is not based on an agreed national standard. Confidence in the use of GrassGro increases where users are already familiar with GrazFeed, which contains an identical animal model. A key component of the commercial release of GrassGro is the provision of an intensive training course. Future adoption of the DS tools will be enhanced by their innovative use in teaching programs such as that at the University of New England where they are used in all undergraduate years of the rural science course.

Feed gaps in mixed-farming systems: insights from the Grain & Graze program

A central concern of the Grain & Graze research, development and extension program has been improving the management of the feedbase on mixed farms through addressing ‘feed gaps’ – times of year during which the supply of forage is insufficient to meet livestock demand. In this review, we use the available data on pasture growth and quality, supplemented by modelling results, to describe the characteristic timing of feed gaps across the Australian cereal-livestock zone. Feedbase interventions studied during the Grain & Graze program have mainly addressed the supply side of the feed balance equation. We review these studies, paying particular attention to the time scale of the variability in the feed balance that each intervention is intended to address. We conclude that grazing of cereals (either dual-purpose or forage crops) is the most promising means of alleviating winter feed gaps in regions where they are important. Reducing feed gaps in summer by relying on unpredictable summer rainfall events will increase year-to-year variability in forage production and will therefore require more flexible livestock management systems to exploit it. The use of forage shrubs offers a practical tool for increasing the predictability of summer and autumn feed supply, but given their moderate capacity for providing additional metabolisable energy it remains important to carefully manage livestock over autumn and to manage the herbaceous inter-row pasture. Feed gaps mainly arise from an interaction between biology and economics. We find, however, that the options studied in the Grain & Graze program for addressing feed gaps require either greater complexity in pasture and grazing management or more opportunistic livestock trading; they therefore come at a cost to the manager’s limited decision-making time. Times with feed gaps are also times when particular natural resource management risks (especially erosion) need to be managed. Supply-side interventions to relieve feed gaps will generally use more soil water, which will often have positive effects on natural resource management outcomes.

Dual-purpose cereals: Can the relative influences of management and environment on crop recovery and grain yield be dissected?

Growing cereal crops for the dual-purposes (DP) of livestock forage during the early vegetative stages and harvesting grain at maturity has been practised for decades. It follows that scientific experiments using DP crops are nearly as old. A survey of more than 270 DP crop experiments revealed that the average effect of crop defoliation on grain yield (GY) was -7±25% (range -35 to 75%). In light of these results, the first purpose of this review was to assess how alternative crop and grazing management regimes affected forage production and GY. Management techniques in order of decreasing importance likely to maximise grain production include (i) terminating grazing at or before GS 30, (ii) matching crop phenology to environment type, (iii) sowing DP crops 2-4 weeks earlier than corresponding sowing dates of grain-only crops, and (iv) ensuring good crop establishment before commencement of grazing. The second aim was to identify the environmental and biotic mechanisms underpinning crop responses to grazing, and to identify crop traits that would be most conducive to minimising yield penalty. A variety of mechanisms increased GY after grazing. Under favourable conditions, increased GY of grazed crops occurred via reduced lodging, mitigation of foliar disease and rapid leaf area recovery after grazing. Under stressful conditions, increased yields of grazed crops were caused by reduced transpiration and conservation of soil water, delayed phenology (frost avoidance at anthesis), and high ability to retranslocate stem reserves to grain. Yield reductions caused by grazing were associated with (i) frost damage soon after grazing, (ii) poor leaf area development or (iii) delayed maturation, which led to water or temperature stress around anthesis, culminating in increased rates of green area senescence and decreased duration of grain-filling. The third aim was to examine the role of simulation models in dissecting the effects of environment from management on crop physiology. Simulation studies of DP crops have extended the results from experimental studies, confirming that forage production increases with earlier sowing, but have also revealed that chances of liveweight gain increase with earlier sowing. Recent modelling demonstrates that potential for inclusion of DP crops into traditional grain-only systems is high, except where growing-season rainfall is <300mm. Prospective research involving crop defoliation should focus on crop recovery, specifically (i) the effects of defoliation on phenology, (ii) the time-course of leaf area recovery and dry matter partitioning, and/or (iii) development of crop-grazing models, for these three areas will be most conducive to increasing the understanding of crop responses to grazing, thereby leading to better management guidelines.

Improving water productivity in the Australian Grains industry—a nationally coordinated approach

Abstract. Improving the water-limited yield of dryland crops and farming systems has been an underpinning objective of research within the Australian grains industry since the concept was defined in the 1970s. Recent slowing in productivity growth has stimulated a search for new sources of improvement, but few previous research investments have been targeted on a national scale. In 2008, the Australian grains industry established the 5-year, AU

The phosphorus and nitrogen requirements of temperate pasture species and their influence on grassland botanical composition

17.6 million, Water Use Efficiency (WUE) Initiative, which challenged growers and researchers to lift WUE of grain-based production systems by 10%. Sixteen regional grower research teams distributed across southern Australia (300–700 mm annual rainfall) proposed a range of agronomic management strategies to improve water-limited productivity. A coordinating project involving a team of agronomists, plant physiologists, soil scientists and system modellers was funded to provide consistent understanding and benchmarking of water-limited yield, experimental advice and assistance, integrating system science and modelling, and to play an integration and communication role. The 16 diverse regional project activities were organised into four themes related to the type of innovation pursued (integrating break-crops, managing summer fallows, managing in-season water-use, managing variable and constraining soils), and the important interactions between these at the farm-scale were explored and emphasised. At annual meetings, the teams compared the impacts of various management strategies across different regions, and the interactions from management combinations. Simulation studies provided predictions of both a priori outcomes that were tested experimentally and extrapolation of results across sites, seasons and up to the whole-farm scale. We demonstrated experimentally that potential exists to improve water productivity at paddock scale by levels well above the 10% target by better summer weed control (37–140%), inclusion of break crops (16–83%), earlier sowing of appropriate varieties (21–33%) and matching N supply to soil type (91% on deep sands). Capturing synergies from combinations of pre- and in-crop management could increase wheat yield at farm scale by 11–47%, and significant on-farm validation and adoption of some innovations has occurred during the Initiative. An ex post economic analysis of the Initiative estimated a benefit : cost ratio of 3.7 : 1, and an internal return on investment of 18.5%. We briefly review the structure and operation of the initiative and summarise some of the key strategies that emerged to improve WUE at paddock and farm-scale.

Opportunities and trade-offs in dual-purpose cereals across the southern Australian mixed-farming zone: a modelling study

Grassland production in southern Australia is generally based on phosphorus (P)- and nitrogen (N)-deficient soils. Use of P-fertiliser is necessary for high production in higher rainfall zones and economic pressures are increasing the need to apply fertiliser more widely and consistently. The P and N requirements of 10 temperate pasture species were examined to understand how increased fertiliser use will affect grassland botanical composition. The plant species fell into 2 main groups with respect to their critical external P requirements (P application rates required to achieve 90% of maximum yield) : those with a high requirement (Trifolium subterraneum, Hordeum leporinum, Bromus molliformis, Microlaena stipoides, and Phalaris aquatica), and those with a low requirement (Lolium rigidum, Vulpia spp., Austrodanthonia richardsonii, and Holcus lanatus). The critical external N requirements of H. leporinum, L. rigidum, and B. molliformis were significantly higher than those of A. richardsonii, Arctotheca calendula, and H. lanatus. Species that ‘tolerate’ nutrient stress were relatively abundant in unfertilised grazing systems and tall ‘competitor’ species were dominant in fertilised pasture under low grazing pressure. The abundance of the species present in fertilised pastures grazed for high utilisation was negatively correlated with their relative growth rates and it is hypothesised that this may indicate that abundance was determined by tolerance or avoidance of grazing.