ABSTRACT Australian dry-land crop producers farm in regions with highly variable climate and soil... more ABSTRACT Australian dry-land crop producers farm in regions with highly variable climate and soils. Farmers have responded to the pressures of rising costs by pioneering and adapting new technologies to narrow the gap between actual and water-limited yield. With yields reaching a plateau in many of the developed world’s cropping areas, it is possible that Australia’s leading farmers have similarly closed the exploitable yield gap and require technological breakthroughs to sustainably push the production frontier to new and higher levels. To assess the potential for Australian farmers to continue closing the yield gap, and possibly increase water-limited yield, the long-term farm production records of individual wheat fields of three leading farmers in South East Australia were used to ascertain the applicability of modelling to develop new and innovative practices. The cropping systems simulator APSIM was used to establish the attainable simulated yield based on the farmers’ chosen management inputs for wheat crops over a period of 16–20 years. A strong relationship (r2 = 0.89, RMSD = 508 kg ha−1) was found between actual and simulated yields. This relationship indicates that yield-reducing factors not simulated by APSIM (weeds, disease etc.) were largely controlled on these farms and confirms APSIM’s suitability for this analysis. Over the 16–20 year study period, the average yield gaps on the three farms ranged from 480 to 770 kg ha−1; representing between 74 and 82% of their water-limited yield potential. For these leading farmers, the yield gap is only small and unlikely to be economically exploitable under current management practices. Consequently, three tactical management innovations with potential to improve farm wheat yield and reduce risk were evaluated. One innovation investigated whether farmers practicing no-till crop establishment, who were able to control weeds prior to sowing, could benefit from sowing current cultivars earlier than present-day practice. It was found that leading farmers are already sowing at the optimum time and sowing earlier would not increase yield because of greater risk of frost damage. Two other innovations were found to have practical application. The first used Yield Prophet® to assist farmers decide when to apply in-crop nitrogen fertiliser based on a more complete understanding of nitrogen and water requirements of crops in variable growing seasons. The second innovation involved sowing slow maturing wheat cultivars earlier than current practice but only in years with adequate stored soil water and early season rainfall. Both innovations were found to increase grain yield and reduce risk of over- or under-application of nitrogen fertiliser. Investigation of strategic and tactical management options to increase yield using simulation modelling for subsequent evaluation in the field has the potential to keep Australian farmers at the forefront of innovations in crop production.
ABSTRACT To feed a growing world population in the coming decades, agriculture must strive to red... more ABSTRACT To feed a growing world population in the coming decades, agriculture must strive to reduce the gap between the yields that are currently achieved by farmers (Ya) and those potentially attainable in rainfed farming systems (Yw). The first step towards reducing yield gaps (Yg) is to obtain realistic estimates of their magnitude and their spatial and temporal variability. In this paper we describe a new yield gap assessment framework. The framework uses statistical yield and cropping area data, remotely sensed data, cropping system simulation and GIS mapping to calculate wheat yield gaps at scales from 1.1 km cells to regional. The framework includes ad hoc on-ground testing of the calculated yield gaps. This framework was applied to wheat in the Wimmera region of Victoria, Australia. Estimated Yg over the whole Wimmera region varied annually from 0.63 to 4.12 Mg ha−1with an average of 2.00 Mg ha−1. Expressed as a relative yield (Y%) the range was 26.3–77.9% with an average of 52.7%. Similarly large spatial variability was described in a Wimmera yield gap map. Such maps can be used to show where efforts to bridge the yield gap are likely to have the biggest impacts. Bridging the exploitable yield gap in the Wimmera region by increasing average Y% to 80% would increase average annual wheat production from 1.09 M tonnes to 1.65 M tonnes. Model estimates of Yw and Yg were compared with data from crop yield contests, experimental variety trials, and on-farm water use and yields. These alternative approaches agreed well with the modelling results, indicating that the proposed framework provided a robust and widely applicable method of determining yield gaps. Its successful implementation requires that: (1) Ya as well as the area and geospatial distribution of wheat cropping are well defined; (2) there is a crop model with proven performance in the local agro-ecological zone; (3) daily weather and soil data (such as PAWC) required by crop models are available throughout the area; and (4) local agronomic best practice is well defined.
Simulation offers the most efficient adjunct in education and “refresher” training of medical per... more Simulation offers the most efficient adjunct in education and “refresher” training of medical personnel. However, simulation devices and facilities are expensive and the combination of cost, distance from the training centers, and professional constraints prevent medical personnel in rural and remote regions from simulation-based training. We have demonstrated that fiscal and logistic barriers can be overcome by the implementation of distance simulation methods that we have already developed. However, whenever High ...
ABSTRACT Australian dry-land crop producers farm in regions with highly variable climate and soil... more ABSTRACT Australian dry-land crop producers farm in regions with highly variable climate and soils. Farmers have responded to the pressures of rising costs by pioneering and adapting new technologies to narrow the gap between actual and water-limited yield. With yields reaching a plateau in many of the developed world’s cropping areas, it is possible that Australia’s leading farmers have similarly closed the exploitable yield gap and require technological breakthroughs to sustainably push the production frontier to new and higher levels. To assess the potential for Australian farmers to continue closing the yield gap, and possibly increase water-limited yield, the long-term farm production records of individual wheat fields of three leading farmers in South East Australia were used to ascertain the applicability of modelling to develop new and innovative practices. The cropping systems simulator APSIM was used to establish the attainable simulated yield based on the farmers’ chosen management inputs for wheat crops over a period of 16–20 years. A strong relationship (r2 = 0.89, RMSD = 508 kg ha−1) was found between actual and simulated yields. This relationship indicates that yield-reducing factors not simulated by APSIM (weeds, disease etc.) were largely controlled on these farms and confirms APSIM’s suitability for this analysis. Over the 16–20 year study period, the average yield gaps on the three farms ranged from 480 to 770 kg ha−1; representing between 74 and 82% of their water-limited yield potential. For these leading farmers, the yield gap is only small and unlikely to be economically exploitable under current management practices. Consequently, three tactical management innovations with potential to improve farm wheat yield and reduce risk were evaluated. One innovation investigated whether farmers practicing no-till crop establishment, who were able to control weeds prior to sowing, could benefit from sowing current cultivars earlier than present-day practice. It was found that leading farmers are already sowing at the optimum time and sowing earlier would not increase yield because of greater risk of frost damage. Two other innovations were found to have practical application. The first used Yield Prophet® to assist farmers decide when to apply in-crop nitrogen fertiliser based on a more complete understanding of nitrogen and water requirements of crops in variable growing seasons. The second innovation involved sowing slow maturing wheat cultivars earlier than current practice but only in years with adequate stored soil water and early season rainfall. Both innovations were found to increase grain yield and reduce risk of over- or under-application of nitrogen fertiliser. Investigation of strategic and tactical management options to increase yield using simulation modelling for subsequent evaluation in the field has the potential to keep Australian farmers at the forefront of innovations in crop production.
ABSTRACT To feed a growing world population in the coming decades, agriculture must strive to red... more ABSTRACT To feed a growing world population in the coming decades, agriculture must strive to reduce the gap between the yields that are currently achieved by farmers (Ya) and those potentially attainable in rainfed farming systems (Yw). The first step towards reducing yield gaps (Yg) is to obtain realistic estimates of their magnitude and their spatial and temporal variability. In this paper we describe a new yield gap assessment framework. The framework uses statistical yield and cropping area data, remotely sensed data, cropping system simulation and GIS mapping to calculate wheat yield gaps at scales from 1.1 km cells to regional. The framework includes ad hoc on-ground testing of the calculated yield gaps. This framework was applied to wheat in the Wimmera region of Victoria, Australia. Estimated Yg over the whole Wimmera region varied annually from 0.63 to 4.12 Mg ha−1with an average of 2.00 Mg ha−1. Expressed as a relative yield (Y%) the range was 26.3–77.9% with an average of 52.7%. Similarly large spatial variability was described in a Wimmera yield gap map. Such maps can be used to show where efforts to bridge the yield gap are likely to have the biggest impacts. Bridging the exploitable yield gap in the Wimmera region by increasing average Y% to 80% would increase average annual wheat production from 1.09 M tonnes to 1.65 M tonnes. Model estimates of Yw and Yg were compared with data from crop yield contests, experimental variety trials, and on-farm water use and yields. These alternative approaches agreed well with the modelling results, indicating that the proposed framework provided a robust and widely applicable method of determining yield gaps. Its successful implementation requires that: (1) Ya as well as the area and geospatial distribution of wheat cropping are well defined; (2) there is a crop model with proven performance in the local agro-ecological zone; (3) daily weather and soil data (such as PAWC) required by crop models are available throughout the area; and (4) local agronomic best practice is well defined.
Simulation offers the most efficient adjunct in education and “refresher” training of medical per... more Simulation offers the most efficient adjunct in education and “refresher” training of medical personnel. However, simulation devices and facilities are expensive and the combination of cost, distance from the training centers, and professional constraints prevent medical personnel in rural and remote regions from simulation-based training. We have demonstrated that fiscal and logistic barriers can be overcome by the implementation of distance simulation methods that we have already developed. However, whenever High ...
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Papers by Tim McClelland