Information Notes (Victorian Mallee)
Monitoring wind erosion and land management in the Victorian Mallee Information Note - 2021
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Agriculture Victoria with support from the Mallee Catchment Management Authority (CMA), is monitoring wind erosion risk in the Victorian Mallee by assessing ground cover and land management throughout the year. This work contributes to the understanding of how the region is maintaining ground cover and reducing the effects of wind erosion. Ground cover data is obtained through remote sensing (satellite imagery) technology and roadside surveys combining new technology with existing tried and true methods.
The project aims to link underlying conditions such as soil type and wind erosion susceptibility, with data collected throughout the year including seasonal conditions, crop cover and ground cover to assess wind erosion risk across the Mallee. The project will continue until June 2023 and data collected will be used to help inform land managers in the Mallee region.
Two roadside surveys are undertaken each year across the Mallee CMA region during autumn and spring to collect ground cover and land management information. Crop type data is also derived from satellite imagery to assess the total vegetative cover (TVC), used as a reporting metric, and the percentage of different crop types to produce a crop cover estimate for the Mallee. The use of satellite imagery allows the entire Mallee CMA region to be measured repeatedly and efficiently. The roadside surveys collect on-ground data that assists in the interpretation of data derived from satellite imagery. They provide detailed qualitative information that cannot be produced from satellite images such as evidence of livestock, controlled grazing, sowing trends, stubble, or erosion present.
The 2021 satellite map (Figure 1) showed cereals were the most dominant land cover, covering 72.2 per cent of agricultural land. Legumes covered 10.1 per cent of agricultural land and (oilseeds) canola less than 0.4 per cent of agricultural land.
The 2021 spring roadside survey observed paddocks with primary land cover types (Figure 2). The results followed a similar pattern to the regional satellite-derived crop cover map with cereals being the most abundant land cover of 1141 paddocks surveyed. Less so was paddocks sown to legumes, and oilseeds. The roadside survey also recorded pasture, stubble and bare paddocks being the least abundant of all paddocks surveyed.
A key component of the spring roadside survey is crop management (Figure 3). The spring survey was undertaken at the end of September into October. This survey estimated that 62.1 per cent would be harvested and 1.7 per cent were hay crops. Brown or green manures made up 2.2 per cent of surveyed paddocks. Undetermined crops were either going to go through to harvest, be cut for hay or end up being a failed crop.
There was a substantial decrease in barley sown from 27.7 per cent in 2020 to 13.3 per cent in 2021, and an increase in paddocks sown to wheat, rising from 36.6 per cent to 54.4 per cent (Figure 4). A decrease in oats, from 4.2 per cent to 2.3 per cent was also recorded. Whilst there was a marginal increase in lentils sown, decreases in paddocks sown to chickpeas, faba beans, lupins, vetch and canola were also seen.
Favorable weather conditions are conducive to high levels of ground cover as seen in 2020, following the dry seasonal conditions observed in 2019. However, there are other factors that can influence ground cover levels, such as crop selection and management practices.
Similarly, crop selection is also based on climatic conditions which also affect ground cover. For example, barley proved to be suitable choice in 2019 given the dry conditions, the remaining stubble is good wind erosion protection. The decline in barley in 2021 is considered to be a result of uncertain global markets, rather than more favorable weather conditions, and was replaced by wheat in the rotation.
Legumes, on the other hand, are an important part of a crop rotation, providing nitrogen to the soil, feed for livestock and diversity in the business. However, if not managed well there is a risk of reduced ground cover as crops are cut lower to the ground. Farmers responded quickly to a good seasonal break in 2020 and good summer rain in 2021, which prompted an increase in lentils with little change in other legumes, taking advantage of higher soil moisture.
Annual and growing season rainfall across the Mallee was higher in 2020 than 2021, yet in general, land system total vegetative cover targets were met more frequently during 2021 compared with 2020.
At a regional scale, the target threshold of area protected from wind erosion was met in all months during both 2020 and 2021 for the Mallee region and agricultural land within the Mallee CMA reporting units.
At a more localised scale, all land systems met their relevant land system specific target for at least nine months in 2021.
It is well known; favorable weather increases vegetative growth. However, best practice management by farmers is key to retaining it regardless of the weather. Crop selection, stubble height, and controlled grazing, contribute to reducing the risk of wind erosion in the Mallee.
This project is supported by Mallee Catchment Management Authority, through funding from the Australian Government’s National Landcare Program, in partnership with Agriculture Victoria.