Anthony Stibbard has over 7 years experience in the Australian agriculture sector in broadacre cropping and livestock. His academic Agronomic background together with working farm experience brings a theoretical and practical mix to his role as an Account Executive for New South Wales, Australia.
Feb 10, 2022
Pre-emergent herbicides play an integral role in both weed management and herbicide resistance management in Australian farming systems. Pre-emergent herbicides take the pressure of post-emergent chemistry and allow growers to have a longer chemical rotation. By rotating herbicide groups growers are reducing the selection pressure and the likelihood of developing herbicide resistance. Another major benefit of using pre-emergent herbicides is the reduction of competition from weeds as the crop is germinating. If a successful pre-emergent spray has been applied, the crop can establish quicker and once it matures, it becomes far more competitive against weed infestations. Understanding your paddocks weed spectrum The key to an effective pre-emergent program is understanding how the herbicides you are using interact with the environment and also the weed spectrum you are attempting to control. Aligning your herbicide choice, and application strategy will result in an improvement in efficacy of pre-emergent herbicides. Assessing the stubble load and ground cover Once you have understood the weed spectrum in the paddock, the next step is to assess the stubble load and ground cover. Both standing and laying stubble will intercept the pre emergent herbicide during spraying resulting in a patchy or uneven application. Knowing how the herbicide will bind to organic matter will help in these types of decisions. For example, some herbicides bind tightly to organic matter, and even with subsequent rainfall will either very slowly wash into the soil, or in some cases with herbicides such as trifluralin, will not wash off at all. Early assessment of groundcover will help make decisions to alter the herbicide strategy, use tools such as tillage or stubble management to result in a successful pre-emergent application. Herbicide loss through volatilisation The next herbicide property which needs to be understood is the volatility of the herbicide. A volatile herbicide will transition to a gaseous state if left on the soil surface. The longer it is left on the surface, the more it will break down. Herbicides such as Triallate and Trifluralin are highly volatile. When using volatile pre-emergent herbicides, incorporation needs to occur soon after spraying to minimise herbicide loss. Other herbicides such as Atrazine or Pyroxasulfone have much lower volatility, in most instances mechanical incorporation is still recommended however some herbicides can be applied to the soil surface and incorporated via subsequent rainfall with minimal losses. Understanding the herbicide solubility is also important in successful pre-emergent strategy. A highly soluble herbicide such as clopyralid requires very little rainfall for incorporation. However, this high solubility also means the herbicide will move readily with soil moisture. And can be prone to leaching into the root zone of the crop and in some instances crop damage can occur. Conversely, a herbicide with a low solubility will require larger amounts of moisture to be incorporated and will not as readily move through the soil profile. Certain crops are also susceptible to crop damage from registered pre emergent herbicides. When poor seed placement, incorrect herbicide incorporation or large amounts of rainfall damage to the emerging crop can result. Taking extra care at sowing time to physically displace the herbicide away from the seed without throwing the soil into the adjacent furrow is important. Placing seed at depth also provides physical distance between the seed and the herbicide and reduces the likelihood of crop damage occurring. Pre-emergent herbicides are an important tool to minimise the impact of weeds in our cropping systems. Getting the most out of your applications is important for maximising returns and to keep the weed seed bank to a minimum. There are some technicalities that go with pre emergent herbicides and no 2 herbicides work and interact with the environment in the exact same way. Therefore, it is always important to follow the label recommendations and get some advice from your agronomist before deciding the best product to use. Learn more To find out more about our pre-em herbicide range of products available to help your farming operation, please visit fbn.com/en-au/direct .
Dec 09, 2021
The recent announcement by the Bureau of Meteorology that a La Niña weather pattern has developed in the tropical Pacific is likely to be short lived in meteorological terms but persisting into late summer or early autumn. This weather pattern will result in above average rainfall across northern and eastern Australia during summer. Higher chances of rainfall events, coupled with global chemical supply shortages, which have resulted in price increases means growers need to plan ahead to maximise their chemical applications this summer. Using quality water when spraying is important to get the most out of your chemical and in turn getting better results on the ground. Summer fallow spraying in Australia comes with its challenges as is. Adverse conditions, wind and other elements all affect the quality of results. Water quality can also drastically affect the efficacy of certain herbicides. Water testing is important to understand the key elements (pH, Hardness, Turbidity and Salinity) which may be resulting in a reduction in efficacy. Water pH Water pH is the measure of acidity or alkalinity of your water and is measured on a scale of 1 (highly acidic) to 14 (highly alkaline). Bore water in Australia tends to be alkaline and this can result in issues when being used in a spray solution. Certain herbicides, when added to alkaline water can dissociate in solution resulting in less active ingredient being available in the spray solution, and in turn reducing the effectiveness of your application. It is advisable to understand the pH of your water and then if required a buffering agent such as Tebuf 700 can be added to water to reduce the pH. Buffering agents work by reducing the pH to a certain point but will not continue acidifying your solution if more is added. Other straight acid products will continue to acidify your solution the more you add. Water Hardness Bore water in Australia often has a high content of Magnesium, Calcium and bicarbonates. These cations and bicarbonates present in the water can bind to certain active ingredients in solutions, which reduces the effectiveness of your spray. Glyphosate and 2,4-D Amine are 2 commonly used herbicides which will have reduced effectiveness if used in water with a high concentration of cations or bicarbonates. Ammonium sulphate can be used to reduce the hardness of water and improve the effectiveness of your spray solution. The standard rate for spray grade AMS is 800g/100L but it is strongly advised to get a water test done, to assess the overall hardness in order to adjust the rate as required. Turbid Water Dirty water can also affect the quality of your spray solution. Certain products such as Paraquat binds tightly to clay molecules in the solution and will reduce the overall effectiveness of your spray application. Spraying with dam water is usually not advised but is required in some instances. Choosing the right products to use with dirty water is important and the addition of additives such as Alum can also be used to purify your water. Salinity Salt in solution is very common in bore water around Australia. High saline levels can also result in some herbicides dropping out of solution, a reduction in spray effectiveness. Diluting the saline water with rainwater can help to reduce the salinity. A test to understand the overall salinity in your water is important to determine suitability for spraying. Water testing is strongly advised in order to get the most out of your herbicides and improve the quality of your summer fallow sprays. If you are looking for more information on where to access water tests get in contact with your local Department of Agriculture representative. Water test strips are also available for purchase, these test strips can be used in the field and give a good indication of pH and hardness. To find out more about products available to help your summer fallow spraying, please visit fbn.com/en-au/direct Resource http://www.bom.gov.au/climate/enso/