Ground Cover Standards. for Central Queensland Grazing Lands

Transcription

1 Ground Cover Standards for Central Queensland Grazing Lands

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3 Ground Cover Standards for Central Queensland Grazing Lands Compiled by Gina O Sullivan, Grazing Land Management Officer, Fitzroy Basin Association.

4 Fitzroy Basin Association is funded by Australian and State Government programmes. Ground Cover Standards for Central Queensland Grazing Lands has been prepared with due care and diligence using the best available information at the time of publication. FBA holds no responsibility for any errors or omissions and decisions made by other parties based on this publication. Acknowledgements: Thanks to Felicity Anderson and Gavin Peck of the Fitzroy Basin Association. For more information contact: Fitzroy Basin Association Inc Level 4, 34 East Street PO Box 139 Fitzroy Basin Association Inc, December FBA

5 Contents Why assess ground cover?... 2 What is ground cover?... 4 How much ground cover do I need? What influences ground cover?... 8 How do I maintain ground cover levels?... 9 Assessing ground cover using photo standards % Ground Cover Low % Ground Cover Moderate % Ground Cover High % Ground Cover High Ground Cover Recording Table Resources and References... 15

6 Ground Cover Standards for Central Queensland Grazing Lands 2 Why assess ground cover? Maintaining adequate ground cover is critical for good grazing land management. It is the most efficient way to maximise the capture of rainfall by enabling it to infiltrate into the soil. Knowing how to assess and look after your ground cover will increase pasture productivity and soil health and help to drought-proof your land. Areas of low ground cover use rainfall inefficiently due to increased runoff and the loss of nutrients and topsoil. By maintaining adequate levels of ground cover the infiltration of rainfall is increased and the health and productivity of the soil and the pasture are improved as the nutrients and topsoil remain in the paddock. When the soil and pasture are healthy, they are more resistant to drought and seasonal impacts and recover quicker after stress. While maintaining good ground cover brings substantial on-farm production and sustainability benefits, off-farm it improves the quality of water in creeks and rivers which flow to the Great Barrier Reef. Ground cover improves productivity and landscape health by: }} Reducing raindrop impact on the soil surface (see Figure 1) }} Slowing/halting water flow across the soil surface }} Improving water retention and infiltration into the soil }} Reducing erosion and runoff of sediment and nutrients }} Providing a source of organic matter in the system. Ground cover also limits the detrimental effects of sun and wind, which include: Sun }} Evaporation of water }} Increases in ground temperature to a level that severely restricts the activity of soil microbes. Wind }} Removal of loose topsoil }} Evaporation of soil water.

7 Figure 1: Ground cover protects soil from raindrop impact. Protected soil surface High Infiltration Exposed soil surface Capped soil surface Low Infiltration Droplets loaded with dislodged soil particles Raindrop Soil Crumbs Water cannot infiltrate and is lost from the site as runoff Arrow indicates water movement Effect of rain drop impact and water movement on covered soil. Effect of rain drop impact and water movement on bare soil. Effect of rain drop impact and water movement on capped soil surface. Plants protect soil from the impact of the raindrops. Water is able to infiltrate the soil. Bare ground is exposed to the full force of raindrops. The impact shatters soil crumbs and the fine particles seal the soil surface. Dislodged soil particles have blocked soil pores to form a cap, leaving no holes for water to enter the soil. The water is forced to run off. Bare ground exposes soil to raindrop impact, which destroys soil crumbs, breaking them into individual soil particles, as shown in Figure 1. These small particles clog pores between remaining soil crumbs, causing soil capping (crusting) and decreasing infiltration rate. Soil capping causes water to flow across the surface, carrying soil with it. Instead of rainfall being used for pasture growth, it flows off to neighbouring areas downstream, taking soil and nutrients with it. Ground Cover Standards for Central Queensland Grazing Lands 3

8 Ground Cover Standards for Central Queensland Grazing Lands 4 What is ground cover? Ground cover consists of any material covering the ground up to 50cm high that will intercept a vertically falling rain drop. Ground cover includes: }} Living and dead plants }} Plant litter }} Bark/leaves }} Pebbles and rocks }} Dung. Grass tussocks slow water flow across the soil surface, reducing erosion and trapping sediment, thus preventing soil loss. The more robust the tussocks and the closer together they are spaced, the more water will be trapped and slowed. Plant roots also promote biological activity in the soil and form channels through the soil which aid infiltration. Ground cover is either attached to the soil (pasture plants) or detached (litter). Although any type of ground cover benefits the paddock, attached, organic ground cover is more effective than detached ground cover in decreasing erosion as its roots prevent it being washed away. Attached cover will also persist through a number of seasons, as will logs and rocks, providing long lasting cover to the soil surface.

9 How much ground cover do I need? Ground cover is a basic measure of how well the soil surface is protected from erosion. There are critical levels of cover below which the soil surface is not effectively protected. A level of 30% ground cover has been identified as a key threshold. Below this, soil loss increases exponentially as cover reduces through runoff and erosion. Below 30% cover = Low Soil loss more than doubles and runoff rapidly increase in areas of less than 30% cover (see figure 2). Areas of bare ground begin to link up, which create flow patterns through the paddock and landscape. 30 % - 50 % cover = Moderate The minimum recommended level of ground cover is 30%. Levels of cover above this threshold lead to much increased infiltration and reduced soil loss as a result of runoff and erosion. The amount of runoff at 50% cover is half the amount at 30% cover, indicating that a target of 50% can double your rainfall utilisation. However ground cover levels between 30% and 50% still indicate a moderate erosion risk. Above 50% cover = High Maintaining ground cover above 50% is essential to minimising runoff, loss of nutrients and soil, and for promoting forage production. High ground cover means less runoff and better land condition. For sloping lands this 50% figure should be increased depending on the steepness and length of the slope (see Figure 3). Ground Cover Standards for Central Queensland Grazing Lands 5

10 Ground Cover Standards for Central Queensland Grazing Lands 6 Figure 2. Relationship between ground cover and soil loss (t/ha). 20 Annual Soil Loss (t/ha) Soil Cover (%) The relationship between increased levels of ground cover and reduced runoff is clearly demonstrated in Figure 2, which shows the results of a study conducted at Springvale between 1887 and Springvale is situated 75 km west of Emerald in the Nogoa River catchment.

11 Figure 3. Sediment in stream which has travelled from up the slope. Ground Cover Standards for Central Queensland Grazing Lands 7

12 Ground Cover Standards for Central Queensland Grazing Lands 8 What influences ground cover? Influences on ground cover fall into two main categories: management, and external factors such as climate. Ground cover levels are most important at the end of the dry season leading into the wet season. While adequate cover levels are desirable throughout the year, late spring and summer represent the period of greatest erosion risk. During this time of the year ground cover from pasture is generally at its lowest. Rainfall at this time increases the risk of large soil losses through erosion because the soil surface has little protection. Ground cover is the most effective way of ensuring runoff and soil erosion are reduced. It is therefore crucial that ground cover levels are maintained above the threshold level of 30% coming out of the dry season. of 30% ground cover should be maintained at all times. A minimum of 50% ground cover will protect your soil in the majority of cases. Consider ground cover when making management decisions, as it is the most important tool you have to optimise rainfall, protect against erosion and ensure you maintain your soil health: one of the most important grazing assets. Maintaining good ground cover isn t always easy, particularly in adverse climatic conditions. Although each property is different, an absolute minimum

13 How do I maintain ground cover levels? Grazing strongly influences ground cover levels, thus managing grazing is the key to managing ground cover. Fire and cropping management practices also have a major impact on ground cover levels. Ground cover is closely associated with land condition. Maintain your ground cover and you will maintain your land condition. Monitoring the condition of your land requires a long-term outlook. Pastures need to be managed so that adequate levels of cover are maintained on the soil surface. Monitoring ground cover is an important part of pasture monitoring and over time will provide a true picture of what is happening in the paddock. Looking down into your pasture, rather than across or through it gives you a good indication of how much ground cover there is. Monitoring ground cover levels over time can give you an indication of whether land condition is being maintained, improving, or going backwards. This can be an important warning sign, and can allow you to adjust grazing management as necessary. Assessing ground cover using photo standards Now that you know how much ground cover you need, the next step is to measure how much cover you have. These photo standards are designed for use in the paddock for rapid assessment of your pasture and soil resources by comparing paddock ground cover levels with the photos. This resource should complement existing management practices of pasture and soil assessment. Important factors to take into consideration when using photo standards to assess ground cover are: }} Ensure a reasonable distance from watering points }} Monitor different land types separately }} Measure representative areas of the paddock if you are aiming for an average ground cover measure }} If taking photos to monitor changes in ground cover over time, include a tape measure in the photo, or something 1m long to be able to compare to the metre square photo standards. Ground Cover Standards for Central Queensland Grazing Lands 9

14 Ground Cover Standards for Central Queensland Grazing Lands 10 30% Ground Cover Low

15 50% Ground Cover Moderate Ground Cover Standards for Central Queensland Grazing Lands 11

16 Ground Cover Standards for Central Queensland Grazing Lands 12 70% Ground Cover High

17 100% Ground Cover High Ground Cover Standards for Central Queensland Grazing Lands 13

18 Ground Cover Standards for Central Queensland Grazing Lands 14 Ground Cover Recording Table Paddock Name Date Site Number (e.g. 1,2,3...) Land Type Ground Cover % Comments (e.g. seasonal conditions, grazing pressure) Average Cover = total % cover number of sites

19 Resources and References Visit the FBA web site for the following resources: }} Fact Sheet: Assessing ground cover in grazing lands of the Fitzroy Basin (FBA ) }} Fact Sheet: Neighbourhood Catchments (FBA ) }} Fact Sheet: Fitzroy Basin Association s Satellite Imagery Project: Mapping for the CQ Community (FBA ) or contact our GIS team on (07) }} Fact Sheet: Property planning: Fencing to landtype Riparian lands (FBA ) }} Fact Sheet: Property planning: Using off-stream watering points (FBA ) }} Fact Sheet: Property planning: Sustainable grazing on riparian lands why and how to do it (FBA ) References: Aisthorpe, J. and Paton, C., Stocktake: Balancing supply and demand. Queensland Department of Primary Industries and Fisheries Chilcott, et al, Grazing Land Management Fitzroy Basin Version, Workshop Notes. Meat and Livestock Australia Limited. Tongway, D. and Hindley, N., Assessment of soil condition of tropical grasslands. Ground Cover Standards for Central Queensland Grazing Lands 15

20 A quick and easy tool to assess your ground cover. It s vital to have an understanding of how much ground cover you have on your property so you can make the right management decisions. These ground cover photo standards have been developed by Central Queensland s leading natural resource management group, the Fitzroy Basin Association Inc., to give land managers a convenient reference they can use in the field. Questions? Contact the Regional Coordinator for the Sustainable Landscapes program on (07)