Improving pasture production without renovating?

Ryegrass sward, Landfall, Tamar Valley
Ryegrass sward, Landfall, Tamar Valley

Olivia Woodiwiss (email)

As pasture yields drop and weedy species take over, many of us assume this is the distress signal that pasture renovation is imminent. Often, how positively preferred pasture species (such as ryegrass, cocksfoot, phalaris, fescue, brome, kikuyu and prairie grass) respond to effective grazing strategies is underestimated. By improving utilisation and nutrient management we can have a greater effect on pasture persistence and production.

It’s important to consider the persistence of a perennial grass pasture species via tillering, not seed, as each tiller can survive independently with its own leaves and root system. Therefore, we want to encourage that plant to tiller as much as possible to improve overall persistence and production. Tillering is encouraged by adequate light interception and nutrient supply – both of which we can significantly influence.

Firstly, for nutrients, we recommend conducting soil tests every other year to ensure nutrient availability is sufficient for a pasture-based system. Soil pH is always the main priority as this can limit the availability of nutrients for the plant. This is followed by addressing any other macro nutrient deficiencies, particularly phosphorous.

Secondly, to ensure adequate light can get to the base of the parent plants, grazing is our best option. Ideally, we want to be rotationally grazing in a fashion that allows enough time for the plant to recover and, at the same time, reduces shading of the base of the plant. Especially at key times of the year (such as spring and autumn), when growth rates are at their peak.

Immediately post grazing, the plant uses the energy reserves in its base and roots to push out the first leaf. Following emergence of the first leaf, root regrowth resumes before the second and third leaves emerge. By frequently removing the leaves (as per 3-leaf rotational grazing practices), the plant is encouraged to build root mass (Figure 1) and increase energy reserves which stimulate a higher yield (kg DM/ha). A larger root mass creates stronger plants that have greater access to water at depth and soil nutrients, which promotes the growth of new tillers and their persistence. This grazing strategy also improves the ability of the pasture to outcompete weeds (such as barley grass, fog grass and broadleaf weeds), which don’t respond so well to being rotationally grazed.

To achieve this, we need to ensure the pastures are being fully utilised. Here, the concentration is on grazing intensity - which is a function of stocking rate and the length of time livestock remain on the pasture. Best practice is to allow livestock two to three days on one allocated area to reduce selective grazing. If this isn’t practical, then reducing the amount of time spent in one area, where possible, will still be beneficial. After grazing, the first leaf is like candy to livestock, and they will repeatedly graze that small, ‘sweet’ leaf over any other available feed. This results in overgrazing of those most favourable pasture species, leading to retardation of the root system, decrease in tiller emergence, undesirable nutrient ratios and eventually the weed species outcompeting them. Optimal grazing areas and frequent movements are key to ensuring livestock graze all pasture on offer.

Overall, the benefits of a new pasture variety will be limited if we haven’t already maximised production through improving soil nutrition, grazing management and then weed control.

Pinion Advisory offers a pasture management course, Pasture Principles. Pasture management is a fundamental skill that determines the profitability of pasture-based grazing systems and is the key driver of stocking rate. Held over 12-months, the sessions align with key seasonal pasture management timeframes and supports producers to make proactive decisions for their business. Pasture Principles has been attended by over 100 businesses in South Australia, Victoria, New South Wales and Tasmania.

Effects Of Long Term Grazing

Figure 1 Effects of long-term grazing at 1-leaf, 2-leaf and 3-leaf on
pasture root growth (Source: NRM South)