Pasture Report: Marcollat Flat Proposed DrainPrepared for
Rob Kemp, Senior Project Officer,
USE Integrated Catchment Management Program Background BACKGROUNDIn April 2004, Rob Kemp Senior Project Officer, USE Integrated Catchment Management Program, approached Rick Jordan, Senior Pasture Systems Consultant, Horizon Farming, to view and assess pasture on three properties on the Marcollat Flat, and provide views on the impact of a proposed drain on the pasture systems on these properties. Horizon Farming is an independent consulting company with substantial experience in pasture systems across South Australia, Victoria, Western Australia and various other areas in Australia. Pasture and grazing systems establishment and management total approximately eighty percent of Horizon Farming consulting and corporate work. Whilst Horizon Farming takes every effort to minimise environmental impacts of pasture and grazing management, we are not environmental experts. Nor are we hydrological or engineering experts, and information in relation to these fields of expertise in this report is not an expert opinion, just our opinion through experience. Horizon Farming was employed to write this report solely as experienced consultants on pasture systems. The proposed drain two (2) metre deep drain discussed in this report is to run north - south along the Marcollat Flat, parallel and in close proximity to, the Marcollat Watercourse. The proposed drain is intended to begin south of Willalooka Pastoral Co and run north to adjoin the already constructed Didicoolum drain (see Map 3). At least seven properties will be directly affected by the proposed drain, and it will run through six of those properties, extensively through some and on the boundary of others. Further properties may be affected by a deep drain however this paper is based on the properties where the drain is proposed to be constructed, and those directly east. This paper is written to provide our opinion of the impact of the proposed drain on the pasture base on five of the directly affected properties which include Longeronong (Willalooka Pastoral Co.), P Vercoe, Kyeema (D & S Prosser), Minnamurra (T Truscott) and Amherst (I Johnson). Property visits were made to three of the directly affected properties (Longeronong, Kyeema and Minnamurra) where pastures and soils were observed and information sought from property owners/managers on the pastures, soils, soil water, grazing management and the proposed drain. Grazing production capabilities of the properties visited cannot be totally quantified without further research, measurement and on-farm trials. Therefore any production capability information stated in this report is from our past experience in pasture systems in similar country; researched material related to this report; notes and reports provided to us; and anecdotal information. The areas of focus in this report include the current pasture status; soil description; current effects of surface water; grazing production and management; and the potential effects of drainage on pasture and soils. Some of the phenomena stated in this report, such as inundation; movement of local / upstream water (both surface and sub soil flows); rising water table; and decline in pasture species and productivity have not been viewed directly by the authors in this locality, in relation to this report. This is due to the seasonality, or long term nature, of the conditions, and the limitations of a single visit to the properties at the end of April 2004. The conclusions drawn by Horizon Farming in relation to these phenomenons are through experience, research and information collected in compilation of this report. The information provided in this report should be used in conjunction with relevant environmental, hydro geological and engineering information to ensure that any drainage works carried out do not adversely affect the productive and sustainable, agricultural and environmental systems, already in affect. The information contained in this report has been collected and collated with due diligence by Horizon Farming. The opinions of landholders, as related to Horizon Farming, have been recorded as accurately as possible. The opinions of Horizon Farming are independent, and unless stated, by no means the opinions of the landholders or any person involved in the project. Horizon Farming has not consulted independently to any of the properties included in this report. The opinions and recommendations of Horizon Farming should not be acted on solely from this report without further collection and analysis of information from either Horizon Farming consultants, or others involved in the project. HORIZON FARMING OPINIONSGenerally the focus area examined is potentially a high producing perennial grass, clover, sub clover and perennial clover based pasture area. This area is capable of sustaining species that persist and produce at higher levels, and maintain quality considerably into the summer, than the surrounding soil types and normal rainfall pattern would sustain in this geographical location. Currently there are varying levels of these pasture species, resultant from a number of factors, including surface salinity, salinity mounds, inundation, and management practices. Presently all areas, apart for the areas directly around the salinity sumps on Longeronong, and the north western areas of Minnamurra, have the potential to produce high quality perennial pasture of this type. See Appendix B for information on suggested mixes for these areas. While there may be isolated pockets within the properties that could sustain Lucerne if drainage was to occur, it is our opinion that this flat is not conducive to good Lucerne production or sustainability. The inundation events would leave the Lucerne prone to crown and root disease and damage. We are unable to provide data on true production figures from these areas within the scope and timeframe of this report. It is our opinion that the perennial pasture base evident on a number of sites, if managed well for fertility and grazing, would produce more dry matter of equivalent quality, to that which could be expected from the Lucerne. This is based on the key winter and spring periods where the density of the existing mixed pasture base would deliver significant advantages in total yield. Lucerne is not as resilient in a grazing situation as a perennial pasture mix. Under grazing (especially set stocking) Lucerne stands decline in density over time, whereas a perennial pasture blend tend to increase in density under correct grazing management. Typically, Lucerne as a single feed source is too high in soluble protein and too low in Neutral Detergent Fibre (NDF), to optimise animal performance. For optimal production, more fibre and an energy balance is required for the Crude Protein percentage. A perennial pasture mix has a range of feed values and nutritive base within it. The legume leaves and shoots in a perennial pasture mix are similar to Lucerne, however the legumes in the perennial pasture mix have older leaves and stems at a lower Crude Protein percentage, with good Metabolisable Energy (ME) and NDF. Solubility of Lucerne in the rumen is much greater than a mixed species perennial pasture. This leads to a
requirement for acclimatisation of the animals onto the Lucerne. A pure Lucerne stand also has the issue of
predisposing animals to bloat. If Lucerne is fed as a sole ration, it is not efficient in utilisation of nutrients. Ruminants (cattle & sheep) evolved on mixed herbage diets, and not on monoculture or single input diets and it Although we are of the opinion the flats described in this report are not suitable for growing Lucerne, we do agree that there are other areas of the properties visited, that are highly suitable for Lucerne production. The parameters of this report are confined to the flats inspected and therefore this report does not quantify the specific areas and production potential of Lucerne, on other parts of the properties visited. Lucerne managed well as part of a farming system and ration, can provide exceptional dryland summer fodder availability and variety in diet for ruminants. In our opinion, the Jip Jip weir is a major issue in the development of surface salinity across the Marcollat Flats,
except in the natural salinity soak areas on Longeronong where it is evident that degrees of salinity have
historically occurred (area B Map 4). The Jip Jip weir may have exacerbated surface salinity in these natural
salinity soaks, however we do not believe it is the main cause. The Jip Jip weir is certainly impacting on the Low soil fertility was visually evident on all pastures viewed and it is believed that they are impacting negatively
on the pasture species present. However, this cannot be quantified by objective data until soil test results are
available. Soil fertility also has potential impact on soil structure though diminished growth and persistence.
Grazing management strategies also impact on persistence of these pastures and the effects of this cannot be It was agreed by all landholders that the surface water that flowed from east to west towards the Marcollat Watercourse was not a major issue. They claimed that this water was fresh and posed no problem to pasture production, even when pastures were inundated. Horizon Farming cannot validate this claim as we have no objective data to support it, however, the fact that all landholders made the claim, leads us to believe that it is true. This is further supported by the fact the pasture decline does not appear to be occurring due to this period of inundation by the moving surface water. It was stated that the surface water can cause an issue if it reaches the Marcollat Watercourse and cannot go any further because the Watercourse is full, and the Jip Jip weir is holding back water. Because this water cannot then flow away at a natural rate, and isn't being utilised by pasture or being drained away by another means, it is contributing to saline and hyper saline environments (through evaporation at the soil surface) on Minnamurra and Longeronong. Water tests and observations in winter when the water is flowing, would need to be carried out to quantify this and should include where the water does become a sheet across the flat. These measurements should also ascertain the quality and quantity of water flowing across the flat at various stages from east to west and north to south. It is our understanding that this work has not been undertaken at this point in time. The pasture systems present on the farms, and those systems that aren't present but have the potential to
be present, rely on the fresh water coming from east to west across the flat. The pasture species described as
the most suitable for this country utilise that water and draw down on it, lowering the water table in summer
while contributing significant amounts of high quality feed over a longer period, allowing for good livestock If the deep or shallow drainage system was constructed along the Marcollat Flat, and it acted as an intervention to the surface water flowing from east to west, it would have the potential to stop water laying on the flat, and may have some impact on reducing water lying in the sump areas, however the negative impacts on the pasture systems and productivity of the whole system would be far greater. A deep or shallow drain constructed north south along the Marcollat Flat would substantially reduce the flow of fresh surface water from east to west, capturing a significant amount of the fresh water flow by taking it north and preventing it from flowing westward. If this was the case, it would most definitely dry the soil profile out and the growing season would be reduced significantly. This would have a major negative impact on the pasture production and could lead to species and pasture productivity decline, as well as soil structural changes, all of which have been outlined previously in this report. It is also unknown and we could not ascertain what impact this would have on land bordering the Marcollat flat areas. Further objective testing is required in this area. It must be noted that a two (2) metre deep drain in the centre or eastern side of the Marcollat Flat, whilst having the potential to draw down in the area of the drain, may not draw down from the salinity sump area on Longeronong and the salinity "mounds" on Minnamurra. It is a real risk that the whole pasture system will be affected by the drain, but the salinity issue in the salinity soak and mound areas may not be affected. A two (2) metre deep drain may also draw saline water from salinity sump areas from west to east. This could lead to saline water adversely affecting pastures and soils as it moves towards the drain. It may also have an effect on properties further east by drawing water towards the drain at a quicker rate than normal, therefore affecting the soil moisture and pasture systems on these properties as well. The saline water drawn into the drain will then be flowing from south to north in the drain, with the potential to leach out into non saline areas (the majority of land on the proposed drain flow pattern) that the drain passes through. The potential for this to occur must be disproved prior to the commencement of drain construction. In the salinity soak areas there is evidence of a soil structure issue contributing to the rising salinity levels. In the areas where salinity is not an issue, the surface water percolates through the profile. However, in the soak areas, the soil structure issue impedes infiltration (due to clay or poorly decomposed organic matter) through the soil profile, causing water to lay on soil surface where evaporation further concentrates the salinity level. In these areas the salinity could be halted through drainage of the soak areas, but not drainage of the whole flat. It is our opinion that by stopping the surface water laying in the salinity soak or salinity mound areas, and allowing draw down or removal of the salts in the profile, as a result of effective flushing by winter rainfall, these areas could be recoverable to some form of productive pasture. The pasture species currently present in the system (especially on Minnamurra) are not alleviating the problem and are in fact possibly contributing to the problem of salinity. However it is recognised that perennial pasture establishment and management on the effected areas of Minnamurra is very difficult due to inundation. The protection and enhancement of the perennial pasture base outside of these areas would in our opinion have significant benefits in reducing the saline areas extending in size. From historical maps, ground water maps and anecdotal information, it could be deduced that the hyper saline areas on Longeronong have historically had high salinity levels and are natural saline areas. While we recognise that this does not favour high pasture production areas, it possibly needs to be managed as a natural saline area and perhaps fenced off and planted on the surrounds with saline tolerant native species or managed as a separate paddock/s with salt tolerant pasture species. Management of saline pasture could also be adjusted to include applications of Urea, either annually of every two years. Research indicates that with Nitrogen application, where 50kg per hectare of Urea is spread, Puccinellia production can increase by 473 - 695kg per hectare annually. It is our opinion that if nothing is done to change this current situation it will extend the saline areas. The natural process is of diminishing of existing vegetation, soil structural changes both leading to surface water ponding and evaporating at the soil surface, further concentrating the salinity levels. In our opinion to alleviate the salinity soak areas on Longeronong, a form of deep drainage is required to allow flushing of the soil profile. We believe this drain needs to be constructed in isolation of the rest of the Marcollat Flat so water is drawn from depth in this area, but has little impact on the rest of the Marcollat Flat system including the other areas on Longeronong itself. Horizon Farming believes that in wet years significant amounts of water do need to be moved from Minnamurra. Currently it is at the end of a large flow of water from the Marcollat Watercourse, and local water from east to west. Once water arrives in the northern boundary of this property, it has very limited places it can go, so it lies and / or backflows south. The result of this is pasture decline due to significant periods of inundation. Perennial species which could assist with draw down of the water table cannot be established, and productive annual species cannot survive through the winter inundation period. As a result only short lived saline tolerant annuals establish in the spring and these have little productive value or ability to alleviate the problem. This is leading to similar issues with evaporation of water at the soil surface and in the root zones of the plant, leading to further concentration of salt. This salt is then unable to be leached from the profile through normal winter rain patterns due to sub soil clays and inundation as discussed. It is imperative for the pasture, production, profitability and sustainability on this property that this water be moved. Due to lack of hydro geographical and engineering expertise, Horizon Farming cannot advise the best option for the removal of the water from Minnamurra, whether by opening of the Jip Jip weir; extending the current Didicoolum drain into the property (but not necessarily all the way along the Marcollat Flat into Kyeema and Longeronong); or the construction of another deep drain, however we are of the strong opinion the water needs to be moved if pasture production is to be increased, more productive species are to be sown, which can then assist in alleviating the problem, all of which will be required for the operation of a sustainable grazing enterprise on this area. CONCLUSIONThe Marcollat Flat has the potential to produce high quality and quantity of perennial grass, sub clover and clover pasture systems. The soil types and winter water flow pattern of the majority of the flat leads to a long growing season of productive pastures. Currently there are varying levels of this potential pasture production due to management, surface salinity and inundation issues. Whilst it is recognised that Lucerne can be a beneficial pasture species, it would not be the most persistent and productive pasture species selection for the Marcollat Flat. Surface salinity and / or adverse inundation occur in isolated pockets on the Marcollat Flat at Longeronong and Minnamurra. The causes of these phenomenon are believed to be from changes in the natural Marcollat Watercourse flow pattern by the construction and management of the Jip Jip weir; historical environmental circumstance; and through increased amount of water upstream on the Marcollat Watercourse. These isolated pockets are low in pasture production and have the potential to encroach adversely on to productive land if remedial action is not taken. The construction of the proposed two (2) metre deep drain may have detrimental effects on the majority of the grazing land across the Marcollat Flat. It is recognised that deep drainage of the northern part of Minnamurra and salinity soak areas of Longeronong will have many positive benefits, as would the permanent opening of the Jip Jip weir, restoring the Marcollat Watercourse to its natural flow pattern. However, building the proposed drain in the proposed location may not have the direct impact on the north western and salinity soak areas of the two properties affected, yet it may significantly affect pastures on the Marcollat Flat that are currently profitable, productive and sustainable. Localised solutions need to be investigated for the isolated problem areas. The generalised solution of theproposed two (2) metre deep drain may cause many known and some as yet unknown negative impacts on what are currently productive grazing systems and the underlying soil structure. It is imperative that the issues on Longeronong and Minnamurra are addressed to facilitate the management of these problem areas and to allow for remedial programs to be undertaken. It is paramount that any of the profitable, productive and sustainable pastures that currently exist on the Marcollat Flat and it surrounds are preserved. Read the entire report. [Adobe PDF 449 kB] |
Marcollat Watercourse (1990) looking south from Keith Kingston Rd. |
