Summer Crops: Relative Water Use Efficiencies and Legacy Impacts in Farming Systems

GRDC - Author: Lindsay Bell (CSIRO Agriculture and Food), Brook Anderson (CSIRO Agriculture and Food), Darren Aisthorpe (Department of Agriculture and Fisheries, Queensland), Andrew Verrell (New South Wales Department of Primary Industries), Jon Baird (New South Wales Department of Primary Industries), Andrew Erbacher (Department of Agriculture and Fisheries, Queensland), Jayne Gentry (Department of Agriculture and Fisheries, Queensland) and David Lawrence (Department of Agriculture and Fisheries, Queensland)

Type: Research Paper
Knowledge level: Advanced

Farm Table says:

The authors of this paper note in the conclusion: “Comparisons of sorghum with mungbean show little differences in residual soil water or soil water in the following crops. However, mungbean performance was affected by the preceding crop. ‘Mungbean after mungbean’ yield was 0.5 t/ha lower than ‘mungbean after sorghum’, despite starting with similar moisture after a long fallow (17/18). In contrast, mungbean yields were similar following short fallows out of sorghum and mungbean (18/19), even though the sorghum left less residual water. These effects are likely to be related to disease reductions rather than soil water or nutrient impacts.”. Please access the full paper via the link below if this research interests you.

The take home messages from this GRDC  funded research are below. Please access the full paper via the link below for methodology, references, acknowledgements and discussion.

  • While summer crops offer rotational options in the farming system, choose the correct crop to match your available soil water and crop history
  • Sorghum is a reliable performer often exceeding other options in terms of $ returned per mm used
  • Cotton and maize require higher water availability and produce less reliable WUE ($/mm). However, cotton has legacy impacts on water availability for subsequent crops that should be considered
  • Mungbean can produce higher $/mm in low water availability situations (<200 mm of rain + soil water). Repeated sowings of mungbeans are likely to induce yield reductions due to disease
  • Sorghum crops sown with > 150 mm of plant available water will maximise crop WUE and profitability. Every extra mm at sowing could be worth as much as $35-70 extra return/ha
  • Higher density sorghum crops may provide greater crop competition against weeds and potential upside yield benefits in good season. We have seen limited legacy benefits (e.g. improved ground cover) or costs (e.g. greater soil water/nutrient extraction) for soil water or nutrient availability.

Figure 1. Relationships between crop water use (in-crop rainfall + soil water extraction) and crop revenue generated amongst 100 summer crops grown in farming systems experiments 2015-2019 (sorghum n= 51, mungbean n = 28, cotton n = 10, sunflower n = 4, maize n = 5).

2020 - Australia - GRDC - Author: Lindsay Bell (CSIRO Agriculture and Food), Brook Anderson (CSIRO Agriculture and Food), Darren Aisthorpe (Department of Agriculture and Fisheries, Queensland), Andrew Verrell (New South Wales Department of Primary Industries), Jon Baird (New South Wales Department of Primary Industries), Andrew Erbacher (Department of Agriculture and Fisheries, Queensland), Jayne Gentry (Department of Agriculture and Fisheries, Queensland) and David Lawrence (Department of Agriculture and Fisheries, Queensland)
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