Variable Rate Application (VRA) in agriculture – a closer look

Variable rate application, or VRA, in the agricultural sector not only allows the farmer to save money, but also assists in optimising yield output, which in turn increases the profitability of a farm. Agriculture contributes no less than 4% to the annual GDP of South Africa. In fact, the produce from this sector contributes to almost all other spheres within the country, so the actual impact is often under-estimated.

The agricultural field currently employs 4, 6% of South Africa’s entire workforce, which accounts for almost 700 000 people directly. Any improvement or optimisation of this industry would directly, or indirectly, impact the entire economy positively.

The impact of VRA technology implementation

The principle of VRA technology can be implemented in more areas than just fertilisation, namely:

• Variable rate seeding
• Variable rate chemical application
• Variable rate fertilisation

In each instance we will provide some general info on its implementation in this area, as well the general impact it could have on your farming system.

Variable rate seeding

The application of seed at a variable rate is not a new concept, as farmers have been applying seed at different rates for years, albeit in a simpler way than today. As an example, Farmers would apply different seed rates depending on whether or not the field had irrigation. As technology has evolved, it is now possible for farmers to use variable rate technology to apply seed at a different rate on different sections in each field. Using data gathered from soil sampling and yield data, a farmer can make informed and up-to-date decisions, which was not the case 20 years ago.

An illustration of the effectiveness of variable rate seeding can be made in a theoretical example. Farmer A has been planting the same maize field for the last 20 years at a rate of 58 000/ha since it is a dry land field. He is aware that certain spots on the field have been under-performing for years owing to a variety of factors, such as nutrient levels, micro-climate conditions and soil structure. Standard practice would be to treat all areas the same with the expectation that results would be similar. An under-performing section of crop land, with no hope of optimal yield potential, constantly pulls down the average yield of the entire field.

In the past, the farmer would not have been able to plant these spots at a different seeding rate, leading to a lower return for that area. VRA has made it possible for the farmer to optimise his planting regime so he can plant these specific areas at a lower seeding rate. He will save on his investment in the long run and also gain a more accurate picture of the potential yield of a given field.

Variable chemical application

The agricultural industry uses millions of litres of chemicals annually to control pests and diseases. It is one of the biggest contributors to the rising input costs that farmers have to contend with, as each year new pests and disease appear, forcing the farmer to take steps to mitigate the impact they may have on productivity.

With the exorbitant chemical bill that the farmer must cover, it is in his best interests to ensure that he applies additives in the most effective way possible. Human error is always a concern with chemical application. Spray rig operators oversee applying the chemicals and, in the past, had to switch the spray boom on and off manually. If they drive out the of the field and only switch it off after 5 metres or so, all that chemical is wasted. Another factor to consider is that in the past sectional control on a spray boom was not yet available which allowed for some wastage through overlap which was unavoidable. Within a given season, this could equate to thousands of litres with a corresponding impact on expenditure. VRA has made it possible for farmers to minimise these losses.

The technology allows a farmer to set field boundaries, so as soon as the operator drives into that field the spraying rig will automatically begin spraying. As soon as the operator leaves that field, it will also automatically switch off. Sectional control of the boom also allows for certain nozzles to be turned on and off depending if the area in question has been sprayed, thus minimising overlap. In most cases a field is also not symmetrical which usually makes spraying difficult. Section control is very helpful in such cases and would save the farmer a lot of money. Variable rate technology also allows the farmer to pre-set the application rates for various fields which further minimises waste.

Variable fertiliser application

Farmers used to use (and still do) fertiliser guidelines that indicate the amount of fertiliser that needs to be applied to obtain a given yield per hectare. The basis of this practice is inherently flawed, as fields are heterogeneous, so crops grown on different parts of the same field will not react the same to a similar amount of fertiliser. Over the years this has been proven true despite arguments to the contrary. Precision soil sampling has shown us that the nutrient requirements on various parts of the field vary, so variable rate technology guides the farmer in applying different amounts for each area. In some instances, this practice can result in drastic savings.

This technology not only assists with the broad application of fertiliser, but also helps when applying fertiliser at planting. As previously mentioned, some areas in a field just do not have the yield potential, so a farmer plants at a lower seeding rate with a lower yield expectation. VRA technology enables an adjustment in planting fertiliser as well.

Farm operators can enjoy the reduction in wastage and higher savings when employing variable rate technology in seeding and additives to their land and crops. Unitrans Africa assists owners with introducing or managing this type of technology that can lead to higher productivity across the board. Their approach in delivering tailored end-to-end solutions has assisted many agricultural concerns in countries like Malawi, Mozambique, Tanzania and Zambia. Reach out to a professional consultant with any agricultural enquiry you may have by making a phone call or sending an email.