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When is the best time to plant legumes in the Brigalow Belt of central and southern Queensland

Page published: December 10, 2024 | Page reviewed: December 12, 2024

In the last Newsletter, we highlighted the importance of planning and preparation in establishing a productive and persistent legume pasture. This edition, we shift focus to determining the ideal planting window, a key factor in ensuring successful establishment.

Establishing legumes in the Brigalow Belt requires strategic planning and timely action to overcome the challenges posed by unreliable rainfall and high evaporation rates. Success is a balancing act between planting the right plant in the right place at the right time in the right way and then managing the young growth until the plant sets seed and the population ‘thickens-up’. Here are some tips to determine your ideal planting window for grasses and legumes in the brigalow belt.

Plant at the right time

The timing of your planting window is critical to success and must be decided early to allow moisture storage and seedbed preparation to begin. In the Brigalow Belt, rainfall patterns provide only a 50% chance of both germination and follow-up rain in any given month, making strategic planning essential. By storing soil moisture through the practice of fallowing, these odds increase to over 90%. Fallowing is common practice in cropping systems but not commonly applied to pasture establishment. The fallowing process (that can be from 3 to 9 months) also allows for the control of weeds and depletes the soil seedbank of undesirable plants, so the new seedlings of your desired species have much less competition for moisture when they are most vulnerable. Fallowing can be either through mechanical cultivation which disturbs the soil and creates a loose seedbed or with the use of a no-till chemical control which holds the soil together until planting and can retain a level of ground cover.

Two months of growth and second germination event. Demonstrating low competition from weeds and grasses.

The length of the required fallow period will depend on your local long term rainfall patterns, soil type and the level of competition from weeds and other grasses. The objective is to store a minimum of 50cm of water in your soil profile (where possible) prior to planting to support your new seedling immediately after germination. In addition to capturing more moisture, a longer fallow will allow for the effective retention of that moisture by eliminating competition from moisture sapping weedy seedlings. As a rule of thumb, approximately 200-250mm of rainfall is needed on fallowed soil to store about 50cm of water in the profile.

Demonstrating importance of stored moisture.

 

Testing the depth of moisture in the profile can be done with a simple DIY moisture push probe, like the one pictured below. These can be fashioned out of steel rod with a handle at the top and the end filed into a tapered point for easy pushing. When pushed down into the soil, the feeling of resistance will change when the soil changes from moist near the top to dry further down the profile. If the length of the push probe is known, it is easy to tell how deep the moisture soil is.

Steel rod fashioned into a push probe with a handle and tapered end. A man pushing on the handle to inset the rod into the soil.
A DIY push probe can be used to assess stored moisture in the soil profile.

Of course, in an unseasonally wet year you can achieve your target moisture earlier than expected and if your soil is warm enough and weeds are under control, then planting can begin early. The risk with an early plant (Nov – Dec) is if follow-up rain doesn’t eventuate, then a period of high heat and dry weather can place extreme pressure on young seedlings.

In the brigalow belt, fallowing is often crucial to ensure that there is enough moisture for legumes to survive and thrive. While direct sowing can work in regions with a reliable wet season (such as north Queensland), it is rarely effective under the challenging conditions of the brigalow belt and is generally a high risk of establishment failure.

Recommended planting windows for legumes in the brigalow belt are:

  • Summer-Growing Legumes: Plant tropical legumes in January to February when rainfall is most likely and to provide ample time for establishment before winter or the dry season.
  • Winter-Growing Temperate Legumes: Plant temperate legumes in autumn, taking advantage of cooler conditions to minimise seedling stress.

By tailoring your approach to suit the specific conditions of your paddock and climate, you can overcome the challenges and reap the benefits of successful legume establishment. In the next edition, we will provide advice on selecting the most suitable planting method for your new pasture.

The content for this article was covered in the webinar on Legume Establishment in Southern and Central Queensland delivered by Principal Pasture Agronomist Gavin Peck in November. The content is also included in more detail in our Persistent and Productive Legume Workshop material. If you would like more detailed information and support please contact us or visit the FutureBeef website for more information and upcoming events.

 

The Queensland Pasture Resilience Program, a partnership between the Department of Primary Industries, Meat & Livestock Australia, and the Australian Government through the MLA Donor Company.