Case study: The benefits of rotating sugarcane crops with grain legumes

Read about trials to improve the productivity and profitability of sugarcane production by rotating crops with grain legumes.

Background

Rather than looking at the benefits of legume crops in isolation, growers wanted trials for optimising legume crops linked with trials to optimise sugarcane crops – bringing the agronomic practices together as one farming system.

Grain legume fallows offer another income stream and have been shown to increase cane productivity.

This project ran in parallel with the co-funded Grains Research and Development Corporation (GRDC) and Department of Agriculture and Fisheries (DAF) Grower Solutions Project (CaneConnection Spring 2021 edition, page 22) which sought to address productivity constraints associated with growing grain legumes in sugar-based farming systems of the Coastal Burnett.

Purpose

  • Raise awareness about the sustainable farming system of rotating sugarcane with legumes.
  • Demonstrate the soil health and economic benefits legume crops can provide for sugarcane growers.
  • Encourage growers to try more sustainable farming practices.
  • Link research being done in legumes to the rest of the farming system.

Summary

When

  • 2017–2020

Location

  • Bundaberg, Maryborough, Childers—Trials took place on local, private properties: Bundaberg Sugar Farms and Isis Cane Services Farms

Who

  • Co-funded by Sugar Research Australia (SRA) and led by the Department of Agriculture and Fisheries (DAF)
  • Local steering committee of growers, agronomists and advisers
  • Project leader: Neil Halpin, DAF

Research

Sugarcane trials were established following the legume trials to examine the benefits to the subsequent cane crops. The 3 trials investigated:

  1. adding organic matter to the surface and deep placement
  2. different fallow management options
  3. the effect of herbicide use strategies.

The trial was carried out on a marginal soil (yellow dermosol) with low water and nutrient holding capacity.

The trial found that adding organic matter had no impact on the productivity of the grain legume crop, or any individual cane crop.

However, there was an impact on sugar yield (an 8.9% increase) achieved through the application of mill-mud/ash blend when cumulative cane crop data (plant + R1 + R2) was analysed.

This productivity response was potentially due to addressing available silicon levels at this site.

The application of mill-mud/ash improved the cumulative sugarcane crop gross margin by $239 per hectare and improved cumulative sugar yield by almost 9%.

Regular sampling was done at the site to analyse soil nutrient and soil carbon properties over time.

The trial assessed which fallow crop had the best economic, soil health and soil nutritional effects. The following crops were compared to the cane monoculture:

  • peanuts (2 varieties)
  • soybeans (2 varieties)
  • mungbeans (2 varieties)
  • pigeon peas
  • a bare fallow.

Peanuts and soybean were best, in terms of boosting grower profitability and productivity of the subsequent sugarcane crop (by more than $2,500/ha compared to monoculture).

Pigeon peas also showed promise as a future rotation crop.

Cane monoculture had the lowest productivity and the lowest economic return of $470/ha.

Peanuts, soybeans and pigeon peas were the most profitable grain legume rotations offering cumulative gross margins (legume break + plant cane + R1) of $4,228; $2,344 and $2,734 more than a monoculture.

Peanuts can provide a number of benefits to the cane farming system.

Data from this field trial suggests that application of herbicides used in the soybean cropping phase has no impact on the productivity of the subsequent sugarcane crop.

However, this trial demonstrated a large difference in the productivity of the subsequent sugarcane crop depending on the variety of soybean grown in the fallow.

The rotation with soybean variety Kuranda resulted in significantly less cane, sugar and dry matter production when compared to a rotation with soybean variety A6785.

Further experimentation would determine the repeatability of the soybean variety effect, and if repeated, could also determine the causal agent.

Successes

  • Annual field day bus tours were popular with local farmers and advisers, who could see the trials for themselves, with 278 people taking part in 3 project field days.
  • Growers were involved in the research process, from ideas generation and trial design, right through to data capture and delivery of results and learnings.
  • The growers met each year to discuss results, and to identify and prioritise issues.
  • The project was seen as particularly relevant to farmers looking to increase their whole-of-farm-economics.
  • An independent survey reported 47% of growers had used information from the trials to make changes to their farming systems.

Outcomes

  • Being involved in the project inspired more than 60% of growers to try a new farming method.
  • Farmers said that the new ideas had encouraged them to rotate sugarcane and legumes to build more profitable and sustainable farming systems.