Production and Environmental Aspects of Cropping Intensification in a Semiarid Environment of Southeastern Australia
Low and highly variable rainfall are major sources of risk for farms in semiarid environments, including the Mallee region of Australia where risk management is largely based on a conservative, low-input approach. This approach has substantial opportunity costs (missing the benefits of wetter seasons) and low yield per unit rainfall. We combined field and modeling experiments to evaluate an intensive, flexible cropping approach based on (i) an opportunistic combination of crops, including wheat (Triticum aestivum L), canola (Brassica napus L.), and grain legumes, and (ii) a close matching of N input to soil and seasonal conditions. In a 4-yr field trial established on a coarse-textured soil, an intensive cropping approach doubled gross margin and halved its coefficient of variation in relation to current practice. Modeling experiments revealed the underlying mechanisms of this response and estimated the effect of cropping intensification on N leaching and deep drainage. Simulated yield improvement under intensive cropping was related to increased water use efficiency [biomass per unit evapotranspiration (ET)] at the expense of N use efficiency (biomass per unit of N uptake); this is consistent with the theoretical expectation that plant growth is maximized when all resources are equally limiting. Simulations indicated no substantial increase in N leaching and moderate decrease in drainage beyond the root zone with the more intensive approach. The approach to intensification in this research provides a platform to improve production and profit and to reduce its seasonal variation with neutral or positive effects on environmentally relevant processes.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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