Stabilising sandy pasture paddocks with low groundcover

Page last updated: Monday, 13 June 2022 - 2:23pm

Producers in the West Midlands region are reminded to closely monitor sandy soils, as conditions from the 2021 season continue to create groundcover challenges in 2022. 

Key points

  • Closely monitor sandy soils for groundcover, especially the paddocks which had low groundcover in 2021
  • Have a plan to actively manage any areas with low groundcover
  • Monitor for grasshoppers
  • Prepare a Plan ‘B’ if seasonal conditions change.
The Department of Primary Industries and Regional Development (DPIRD) has been working with the West Midlands Group (WMG) and producers to investigate widespread areas of sandy soils with low groundcover at risk of soil erosion. The area of greatest concern is from Gingin in the south, to Allanooka in the north and west of the Darling Fault line. The extent of bare soils in late 2021 was unexpected given the favourable growing conditions last year, so we wanted to investigate the causes and develop strategies for producers to mitigate the risk of further erosion.
 
A common denominator across all the sites investigated were high grasshopper numbers during last year’s growing season. Often there were additional contributing factors like a false break, some recent over-grazing, or a low pasture seed bank but these tended to be site-specific. The outcome was loss of topsoil from wind erosion – paddocks with inadequate groundcover were hit with the strong winds associated with passage of Cyclone Seroja in April, followed soon after by other strong wind events.
 
The management guidelines to minimise wind erosion are well understood, refer to Managing wind erosion and Wind erosion in south-west WA
On a positive note, many producers were proactive in controlling grasshoppers that were retarding pasture growth and/or over-sowing pasture paddocks. These producers were largely successful in their remediation, although there were some mixed results. However, some producers took little action in 2021 as they were expecting the grasshoppers to largely disappear over the growing season as is typically the case.
 
It is important to note that our focus is not looking back, but rather looking forward. DPIRD is working with WMG and leading producers to share their experiences about what remediation worked well and what was less successful. Link to case studies: Steele Rudd (Eganu); Don Bradshaw (north Badgingarra). 

Key actions taken by producers in 2021 to increase groundcover and their effectiveness:

Action

Timing

General outcome

Sow cereals and/or a cereal/pasture mix

Early in the growing season

Full groundcover, with good production and no erosion providing not over-grazed

 

Mid-growing season

Good groundcover, with moderate production and a low erosion risk providing careful grazing

Sow sorghum

Late August to September

Mixed results with minimal grazing value
(three properties)

Sow sub-tropical perennial grasses with a cereal cover crop (broadcast)

August–September

Innovative practice and soil stabilised, but achieving optimal perennial plant density depended on receiving sufficient spring rainfall

2022 season

Early autumn rainfall this season has resulted in the germination of annual pastures and the warm conditions have supported good growth of sub-tropical grass pastures. Some of the previously affected paddocks with good pasture seed banks now have reasonable seedling numbers, which should result in adequate groundcover this year given good grazing practices. 

For paddocks or areas within paddocks that have low seedling numbers, this is likely a sign of a low pasture seed bank. For these areas, supplementary over-sowing of a cereal-pasture mix is recommended.

We encourage producers to be proactive and have a plan in place to prevent wind erosion and maximise soil productivity for the 2022 season. Producers also need to prepare a plan ‘B’ in case seasonal conditions change (e.g. false break) and to monitor regularly for grasshoppers. Closely monitor sandy soils, especially those paddocks or areas within paddocks which had low groundcover last year.

Monitor for grasshoppers

High grasshopper numbers were a key factor adversely affecting pasture productivity and groundcover in 2021. The wet summer leading into the 2021 season provided ideal conditions for grasshoppers to breed and their feeding damage decreased pasture density and productivity. The main species identified was the Urnisa grasshopper, also known as the sand grasshopper.

There have been reports from the West Midlands of grasshopper hatchings in early May this year, so we are encouraging growers to monitor and control grasshoppers if pastures are not out-growing the damage Identifying and controlling sand grasshopper.

Tactical and strategic forage options

There are a range of strategies built around improving the feedbase that will help to manage sandy soils with low groundcover and reduce the risk of erosion (Table 1).

Short-term tactical actions include:

  • Over-sowing a cereal into pasture paddocks or areas within paddocks with low groundcover.
  • Exclude grazing from paddocks with low or marginal groundcover (Use confinement feeding or graze perennial pastures) until the groundcover exceeds the guidelines with respect to minimum groundcover: Confined paddock feeding and feedlotting.
  • Over-sow a cereal – pasture mix to build a self-regenerating pasture base for the medium term.
  • Annual cropping with no grazing can be a stable land use on deep pale sands but may not be sustainable in the medium-term.

Soil fertility levels on many of the sites investigated were very low to low for phosphorus, potassium, sulfur and organic carbon, while the soil pH was adequate to satisfactory. These low soil fertility levels will need to be addressed to lift pasture and livestock productivity.

Medium- to long-term actions include:

  • Fencing to soil type to separate more susceptible soils and to ensure paddocks have a relatively uniform carrying capacity.
  • Sowing sub-tropical perennial grasses as well managed perennial pastures should have year-round high groundcover.

Perennial grasses are the most stable option for grazing the sandy soils in the West Midlands and well managed perennial pastures can have year-round high levels of groundcover resulting in a negligible erosion risk. However, good establishment is a key as not all perennial pastures have adequate plant density.

  • Small erosion prone areas like low dunes and sandy rises within a paddock, which are highly susceptible to wind erosion, can be ameliorated by claying or applying gravel on the soil surface to encourage groundcover and reduce the erosion risk.
  • Fence off deep sands which have low agricultural potential and then planting trees with potential carbon sequestration benefits.
  • Planting alleys of tagasaste are a productive, stable land use.

With any re-seeding growers need to regularly monitor for grasshoppers and control according to population thresholds.

Table 1 A summary of forage and fodder options for increasing groundcover and production on medium- to deep-sandy soils in the West Midlands Region. Five-star rating scale from * = low to ***** = high

Option

Comments

Overall suitability

Temperate cereals

Excellent options to increase groundcover in the short-term, however, to ensure good production the soil fertility needs to be adequate. Even if only grazed for a short period, regeneration in the following year can be patchy. Sow as a monoculture, as a mix of cereals or in a mix with pasture species. For soil stabilisation, sow at rates of at least 20kg/ha.

Forage oats and barley

Forage varieties preferred

***

Cereal rye

Used to stabilise sand dunes, quick growth

****

Triticale

Tolerant of a range of soils conditions

***

Annual pasture legumes and grasses

Sub clover

Less suited to the medium- to deep-sands due to a shallow root system, but well suited to shallow gravelly soils Subterranean clover

*

Yellow serradella

Adapted to sandy soils providing adequate nutrition; all varieties are hard-seeded.

‘SerraMax’ is a new variety with good regeneration when seed is buried and is suited to longer-term pastures SerraMax

***

French serradella

Adapted to sandy soils providing adequate nutrition; soft- and hard-seeded varieties
French serradella

***

Annual ryegrass, Italian ryegrass

 

Can be a productive option providing there is adequate nutrition, but potential issues include ARGT (Annual ryegrass toxicity) in stands of Wimmera ryegrass.

***

Herbaceous perennial pastures

Sub-tropical perennial grasses

Well suited to sandy soils, including deep pale sands; provides year-round groundcover.

Risk of soil erosion during establishment, so sow into anchored pasture residues or cereal stubble. Refer section below

*****

Lucerne

Less suited to the sandy soils with low fertility (nutrient deficiencies, soil acidity) Lucerne

*

Tedera

Less suited to the sandy soils with low fertility. Requires well drained soils with good water holding capacity and soil fertility Tedera

*

Woody perennial pastures

Tagasaste

Well adapted to the deep sandy soils and the climate. Usually sown by a contractor.

More easily managed with cattle but can use with sheep. Management information is well understood, but infrequent cutting is required even with well-managed stands.
Perennial pastures for Western Australia

****

Summer growing annual crops and forages

Can be useful options to provide groundcover for paddocks with low groundcover in spring, but production may be low or limited unless there is access to subsoil moisture. Require warm soil temperatures for good germination. Fast growing when conditions are favourable (warm temperatures + soil moisture + fertility). Limited grazing value without risking wind erosion. Need to be re-seeded each year. Refer to: “Guide to growing summer grain & forages in the south coast region, Western Australia”. Summer crops – south coast of WA

Japanese, Shirohie millet

These are temperate grasses so can be sown earlier than the C4 grasses below but limited drought tolerance on sandy soils with low fertility.

**

Pearl millet

Minimum soil temp. for germination 18°C, optimum temp >20°C; drought tolerant, safe for grazing at all growth stages

***

Hybrid forage sorghum

Minimum soil temp. for germination 16°C, optimum temp >18°C; risk of prussic acid (HCN) poisoning especially when grazing stressed or young regrowth (risk varies with ‘type’).

**

Sub-tropical perennial grasses

Observations from 2021 highlighted a stark contrast between annual pasture paddocks with low cover compared with perennial grass pastures on adjacent paddocks with excellent groundcover.

Sub-tropical (warm season) perennial grasses are well suited to the sandy soils in the target region and are the most stable pasture option for long-term grazing paddocks, providing there is a good perennial plant density. They provide year-round groundcover, valuable out-of-season green feed and with good management will be a productive, long-term pasture. The main perennial grasses grown are Panic grass and Rhodes grass which are often sown as a mixture.

The sowing window in this region is from mid-August to early September. To increase production over winter, consider over-sowing a cereal or a companion annual pasture legume like serradella.

If sowing a paddock with low groundcover to perennial grasses in Spring 2022 then plan ahead and consider whether to sow a cereal as a cover crop. Further information refer to: Sub-tropical grass establishment or download Bulletin 4840 Sub-tropical grass establishment Guide

To be productive in the medium-term a perennial grass pasture requires a companion legume to improve the feed quality over the winter growing season and provide the nitrogen input to drive productivity Companion legume options for sub-tropical grasses and these pastures can be highly productive Highly-productive sub-tropical-grass with serradella pastures. Sowing a grain crop into an established perennial grass pasture, also called Pasture cropping can be an option, although a possible grain yield penalty needs to be weighed against additional summer grazing.

Contact information

Geoff Moore
+61 (0)8 9368 3293