Speaker
Description
Introduction
The decision of when and what to plant in a particular field is the decision that faces all farmers. For farmers in regions with variable climates and both summer and winter sowing options, such as the subtropical grains regions of eastern Australia, planting the wrong crop at the wrong time can have severe economic consequences (Angus et al., 1980; Whish et al., 2007), but more importantly influence future economic returns and systems decisions. The final decision on the choice and position of crops in a sequence is tempered by the environment, the personal preferences of the farmer, their risk profile, historic herbicide decisions, existing weed, disease and pathogen burdens, current markets, and prices. However, in variable climates, that rely on stored soil water, a rotation requires specific phases to refill soil water reserves, these phases are referred to as fallows.
Despite the acknowledged benefits of the fallows, they are also an area of inefficiency, but their removal has the potential to intensify a rotation and improve profit. Previous studies have examined the pareto-optimal trade-offs within these grain systems and showed summer cropping, and an increase in cropping intensity was needed to achieve higher gross margins (deVoil et al., 2006; Hochman et al., 2020), but this in turn significantly increased financial risk of unprofitable crops. The aim of this paper was to identify key criteria within the system that facilitated the inclusion of opportunity crops to maintain system profitability while minimising the risk of unprofitable crops within the rotation.
Methods
Using historic simulations, the probabilistic relationship between initial soil water and final yield was assessed. Using this knowledge a range of simple rules were developed to identify the circumstances when intensifying a sequence had the best chance of success. These rules were then implemented within the Agricultural Production Simulation Model (APSiM) (Holzworth et al., 2018) and used to compare against current rotational strategies practiced in the region.
Results
Strategically intensifying the rotation by relating current soil water conditions to historic yield probabilities, maintained high gross margin returns while reducing the risk of unprofitable crops.
Discussion
The use of rules was successful; however, they are specific to each environment. The more variable the environment the more valuable the rules. The use of the rules was not always positive, all environments, demonstrated losses caused by the rigidity of the rules, with crops not sown when an opportunity to sow arose just after the rules time frame. However, these losses were easily offset by the reduction in the number of unprofitable crops. Not all decisions have an immediate economic value. On occasions, especially during or after drought, there can be a benefit in planting a cereal crop even when its chance of being profitable is low. This is because systems that rely on the capture of water, need to protect the soil surface to improve infiltration and reduce erosion (Freebairn et al., 1986). These rules do not capture this, but they provided a framework for grain growers to discuss the benefits and costs of their decisions.
References
Angus, J., Nix, H., Russell, J., Kruizinga, J., 1980. Water use, growth and yield of wheat in a subtropical environment. Aust. J. Agric. Res. 31, 873. https://doi.org/10.1071/AR9800873
deVoil, P., Rossing, W.A.H., Hammer, G.L., 2006. Exploring profit – Sustainability trade-offs in cropping systems using evolutionary algorithms. Environ. Model. Softw. 21, 1368–1374. https://doi.org/10.1016/j.envsoft.2005.04.016
Hochman, Z., Horan, H., Navarro Garcia, J., Hopwood, G., Whish, J., Bell, L., Zhang, X., Jing, H., 2020. Cropping system yield gaps can be narrowed with more optimal rotations in dryland subtropical Australia. Agric. Syst. 184, 102896. https://doi.org/10.1016/j.agsy.2020.102896
Holzworth, D., Huth, N.I., Fainges, J., Brown, H., Zurcher, E., Cichota, R., Verrall, S., Herrmann, N.I., Zheng, B., Snow, V., 2018. APSIM Next Generation: Overcoming challenges in modernising a farming systems model. Environ. Model. Softw. 103, 43–51. https://doi.org/10.1016/j.envsoft.2018.02.002
Whish, J.P.M., Castor, P., Carberry, P.S., 2007. Managing production constraints to the reliability of chickpea (Cicer arietinum L.) within marginal areas of the northern grains region of Australia. Aust. J. Agric. Res. 58, 396. https://doi.org/10.1071/AR06179
| Keywords | Farming systems; decision support; simulation modelling; subtropical Agriculture |
|---|
