An Australian contribution to farming systems research in international partnerships

This review of an Australian contribution to farming systems research (FSR) honours Dr R L (Bob) McCown (1937-2017) and his innovations in and advocacy of FSR practice in Australia, Africa and globally. Australian contributions to international FSR development and practice are widely recognized, notably in the CGIAR Centers, World Bank and ACIAR-supported international research partnerships. There has been a resurgence of interest in farming system approaches with the growing challenges of complex, uncertain, 'wicked' problems. McCown's leadership and insights helped shape a particular "Australian-style" of FSR and influenced international FSR practice over four decades, particularly the incorporation of simulation modelling in framing researcher connections with farmers' decision-making. The paper concludes with some priorities for refinement of FSR methods for international agricultural research in the years ahead

Modelling genotypic and environmental control of leaf area dynamics in grain sorghum. II. Individual leaf level

Development of leaf area on tiller axes of grain sorghum (Sorghum bicolor (L.) Moench) has previously either been ignored or treated with over-simplifications in crop simulation models. This paper describes a framework to simulate total leaf area of tillering sorghums based on the prediction of the appearance and expansion of individual leaves. Data were collated from experiments on grain sorghum hybrids grown at locations ranging in latitude from 39-degrees-11'N to 27-degrees-33'S. A leaf area model was developed which simulated axes within plants independently, such that the production and expansion of individual leaves were simulated on the main culm and each developing tiller. The model simulates total leaf area per plant (TPLA) (without losses due to senescence) using functions to predict: (i) the appearance of successive axes on plants as a function of thermal time from emergence; (ii) a constant rate of mature leaf production per axis per unit of thermal time; (iii) the profile of mature leaf areas for leaves on each axis as a function of total number of leaves produced per axis; and (iv) the leaf area contribution of immature leaves at any time as equivalent to that for a constant number of mature leaves. For seven sorghum hybrids grown at three locations, a general model simulated TPLA over time, accounting for 90% of observed variation with a root mean square deviation of 905 cm2 for observed values of TPLA ranging from 161 cm2 to 10584 cm2

Modelling genotypic and environmental control of leaf area dynamics in grain sorghum. III. Senescence and prediction of green leaf area

This is the third paper in a series that examines the genotypic and environmental controls of leaf area dynamics in grain sorghum. In this paper, genotypic variation in leaf area senscence was firstly quantified both at the whole plant level and at the level of individual leaves. Green leaf area was then simulated at both levels, and predictions were compared with independent data on crop leaf area index. At the whole plant level, senesced plant leaf area (SPLA) was modelled as a logistic function of thermal time after emergence, where the asymptote of the relationship is determined by maximum leaf area produced per plant. At the level of individual leaves, where leaf size was predicted, SPLA was simulated by a constant rate of senescence of individual leaves. The relationship at the two levels of simulation were both affected by different leaf numbers per plant. While there were genotypic differences in the senescence of sorghum leaf area, the genotypic control of sorghum leaf area dynamics was generally less influential than the effect of the environment. Relationships to predict SPLA were added to those to predict total plant leaf area (TPLA), previously developed in this series, to enable prediction of green leaf area development of sorghum crops. There was little difference in the accuracy with which the models at the whole plant and individual leaf levels simulated independent data. The model at the whole plant level was simpler and required less initial information. The model at the level of individual leaves was more complex and needed greater information, but provided a more detailed treatment of leaf area dynamics. The choice between the two approaches will depend to a large degree on the demands of the study for which a sorghum leaf area model is to be applied

Modelling genotypic and environmental control of leaf area dynamics in grain sorghum. I. Whole plant level

Leaf area dynamics are controlled by genotypic and environmental influences. In this series of papers, general models of leaf area dynamics of uniculm and tillering sorghum (Sorghum bicolor (L.) Moench) at the whole plant and individual leaf levels were developed to examine and quantify both genotypic and environmental controls. Green leaf area was modelled by examining leaf area production and senescence separately. Data from field experiments involving broad ranges of hybrids and environments were collated and analysed. Crops were grown with adequate water and nutrient supply

Eco-efficient Agriculture: Concepts, Challenges, and Opportunities

Eco-efficiency in the simplest of terms is about achieving more with less—more agricultural outputs, in terms of quantity and quality, for less input of land, water, nutrients, energy, labor, or capital. The concept of eco-efficiency encompasses both the ecological and economic dimensions of sustainable agriculture. Social and institutional dimensions of sustainability, while not explicitly captured in eco-efficiency measures, remain critical barriers and opportunities on the pathway toward more eco-efficient agriculture. This review paper explores the multidimensionality of the eco-efficiency concept as it applies to agriculture across diverse spatial and temporal scales, from cellular metabolisms through to crops, farms, regions, and ecosystems. These dimensions of eco-efficiency are integrated through the presentation and exploration of a framework that explores an efficiency frontier between agricultural outputs and inputs, investment, or risk. The challenge for agriculture in the coming decades will be to increase productivity of agricultural lands in line with the increasing demands for food and fiber. Achieving such eco-efficiency, while addressing risk and variability, will be a major challenge for future agriculture. Often, risk will be a critical issue influencing adoption; it needs explicit attention in the diagnosis and intervention steps toward enhancing eco-efficiency. To ensure food security, systems analysis and modeling approaches, combined with farmer-focused experimentation and resource assessment, will provide the necessary robust approaches to raise the eco-efficiency of agricultural systems. Eco-efficient agriculture: Concepts, challenges, and opportunitie

Row configuration as a tool for managing rain-fed cotton systems: Review and simulation analysis

Rain-fed cotton production can be a significant proportion (average 17%) of the Australian Cotton Industry. One of the management techniques that rain-fed cotton growers have is to modify row configuration. Configurations that have entire rows missing from the sowing configuration are often referred to as ‘skip row’. Skip configurations are used to: increase the amount of soil water available for the crop, which can influence the potential lint yield; reduce the level of variability or risk associated with production; enhance fibre quality; and reduce input costs. Choosing the correct row configuration for a particular environment involves many, often complex, considerations. This paper presents an examination of how rain-fed cotton production in Australia is influenced by row configuration with different management and environmental factors. Data collated from field experiments and the cotton crop simulation model OZCOT, were used to explore the impact of agronomic decisions on potential lint yield and fibre quality and consequent economic benefit. Some key findings were: (i) soil water available at sowing did not increase the advantage of skip row relative to solid configurations; (ii) reduced row spacing (75 cm) did not alter lint yield significantly in skip row crops; (iii) skip row, rain-fed crops show reasonable plasticity in terms of optimum plant spacing within the row (simular to irrigated cotton); (iv) sowing time of rain-fed crops would appear to differ between solid and skip row arrangements; (v) skip row configurations markedly reduce the risk of price discounts due to short fibre or low micronaire and this should be carefully considered in the choice of row configuration; and (vi) skip configurations can also provide some savings in variable costs. In situations where rain-fed cotton sown in solid row configurations is subject to water stress that may affect lint yield or fibre quality, skip row configurations would be a preferential alternative to reduce risk of financial loss

Vegetative nitrogen stress decreases lodging risk and increases yield of irrigated spring wheat in the subtropics

In-crop nitrogen (N) application is used widely in rainfed winter wheat production to reduce lodging risk; however, uncertainty exists as to its ability to reduce lodging risk in subtropical irrigated wheat production without simultaneously reducing yield potential. The objective of this study was therefore to determine whether in-crop N application reduces lodging risk without reducing yield of irrigated spring wheat in a subtropical environment. Irrigated small-plot experiments were conducted to compare the effect of alternative N timing on lodging and yield in two cultivars. Variable N regimes were imposed during the vegetative growth phase, after which additional N was applied to ensure that total season N application was uniform across N-timing treatments. Treatments with low N at sowing had significantly less lodging and were the highest yielding, exhibiting yield increases of up to 0.8 t ha–1 compared to treatments with high N at sowing. Increased leaf area index, biomass and tiller count at the end of the vegetative growth phase were correlated with increased lodging in both cultivars, although the strength of the correlation varied with cultivar and season. We conclude that canopy-management techniques can be used to simultaneously increase yield and decrease lodging in irrigated spring wheat in the subtropics, but require different implementation from techniques used in temperate regions of Australia

Accelerating genetic gains in legumes for the development of prosperous smallholder agriculture: integrating genomics, phenotyping, systems modelling and agronomy

Grain legumes form an important component of the human diet, provide feed for livestock, and replenish soil fertility through biological nitrogen fixation. Globally, the demand for food legumes is increasing as they complement cereals in protein requirements and possess a high percentage of digestible protein. Climate change has enhanced the frequency and intensity of drought stress, posing serious production constraints, especially in rainfed regions where most legumes are produced. Genetic improvement of legumes, like other crops, is mostly based on pedigree and performance-based selection over the past half century. To achieve faster genetic gains in legumes in rainfed conditions, this review proposes the integration of modern genomics approaches, high throughput phenomics, and simulation modelling in support of crop improvement that leads to improved varieties that perform with appropriate agronomy. Selection intensity, generation interval, and improved operational efficiencies in breeding are expected to further enhance the genetic gain in experimental plots. Improved seed access to farmers, combined with appropriate agronomic packages in farmers’ fields, will deliver higher genetic gains. Enhanced genetic gains, including not only productivity but also nutritional and market traits, will increase the profitability of farming and the availability of affordable nutritious food especially in developing countries