Variable Rate Technology in Cotton  


As the cotton season progresses in Australia, growers are starting to apply nutrients, growth regulators and other inputs to their crops. Where growers traditionally tended to apply one blanket rate of product over the whole field, or sometimes even the whole farm, the tendency now is to divide fields up into separate management zones and treat these all differently, depending on the what is needed in that specific zone. The need for more economical and effective applications are the main driver behind the demand for more variable rate input applications. Applying the exact right amount of product at precisely the spot you want to apply it, will help to push the yield and quality of your cotton crop up even further and thus enhancing the bottom line.

Many growers are already setup for variable rate input applications, for example via their boom sprayers, fertiliser spreader, Big-N applicator and in most cases also through their aerial spray operator. Where gas and solid fertilisers volumes can be applied accurately depending on the width of the machine, most boom sprayers and spray planes still rely on variable flow methodology. What this means is that the chemicals or liquid fertilisers are pre-mixed before the application and loaded in the tank. The variable rate script then gets applied by varying the amount of spray volume applied to the field. There are also planes and boom sprayers in operation that use a direct injection technology; in this case your equipment will have 2 or more separate tanks and the right amount of chemical gets added to the water as it is distributed on the field. The main advantage of this system is that you can keep your total spray volume the same across the field and only vary the amount of chemical or fertiliser.  Variable flow equipment however tends to be the predominant equipment currently utilised.

The accuracy of Variable Rate enabled equipment can vary a lot; from a plane applying a 20 meter swath and the ability to change rate within 50 metres to the newest controllers mounted on boom sprayers that allow individual nozzle control and the ability to control rates almost instantly but every machine is different. Whilst extreme accuracy might be desirable in some horticulture or viticulture situations, in broad acre crops like cotton even the most rudimentary system tends to make a significant difference already. Increased accuracy might improve the results you can achieve, but it is important to consider the improvement you can expect when spending large amounts of money on improved variable rate equipment.

So how can you easily start using Variable Rate Technology in your cotton crop? By merely dividing a irrigation field up into three zones for example and applying Nitrogen in increasing rates as you get closer to the head-ditch of the field, you can counter nitrogen wash-down during irrigation. Or you can take a NDVI image of your field, divide the field in different zones according to the biomass index measured, and apply your Mepiquat in three different rates so that each plant gets enough growth regulator to slow its growth down, but not too much so that it gets cut out. Both examples don't require equipment that is not already widely available, can be implemented immediately and will provide an immediate difference to your bottom line. As can be seen in the examples above, individual zones within the fields also do not have to stay the same throughout the crop; quite often you will find that the way the zones are assigned within the field, changes throughout the season.

What is important to consider however when contemplating Variable Rate Technology, is that it should be able to be easily integrated into your current farming practices and support the way you currently manage and grow your cotton. So Variable Rate Technology does not aim to change the way you grow your crop all together, it merely aims to divide your fields up in smaller management zones and treat them separately when assigning input rates.

If you would like to start incorporating variable rate technology into your farming practices to improve your profit margin, or if you would like to advance the Variable Rate techniques you are currently using, please reach out to me on the details below.

Written by: Reinder Prins. Reinder Prins is the Market Development Manager for Cotton Growers Services and as such is responsible for the Precision Agriculture initiatives within the organisation. Reinder can be contacted on +61 427 - 808 489 or via e-mail on reinderprins[at]cgs[dot]com[dot]au.