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Consider Variable-Rate Application to Reduce Fertilizer Costs

Jan 17, 2022 | Written by Simerjeet Virk and Glen Harris

Variable-rate technology may have a bigger pay back this year.

The skyrocketing fertilizer prices has every grower thinking about where and how to reduce the fertilizer costs on their farm to remain profitable this year. In order to better manage fertilizer costs, more growers are looking at ways to be more efficient and cost effective with their inputs and applications. One of the ways where precision agriculture can help growers being more efficient with fertilizer use is through implementation of variable-rate technology. Many research studies over the years have demonstrated the benefits of implementing variable-rate applications with one of the main benefits being the more efficient nutrient use resulting in lower input costs and higher profits. These benefits are further maximized in uneven and non-uniform fields with high inherent spatial variability – whether due to soil type, topography or other soil/crop characteristics. Interestingly, these differences in soil types or topography are hard to miss in majority of the fields in the southeastern US including Georgia, which makes them perfect candidates to benefit from precision ag practices such as variable-rate fertilizer applications.  

While majority of the growers are aware about the spatial variability in their fields and employ some sort of precision soil sampling strategy – grid, zone or composite – to determine the nutrient requirements of their fields, very few “advanced” growers utilize that data and information to perform variable-rate applications. For most others, this information or soil nutrient maps just serves a purpose of determining a best single application rate that can be applied uniformly across the whole field. While applying more fertilizer at places than what’s actually needed means increased costs, under-fertilization means failing to capitalize on the actual yield potential of those areas. Besides inefficient fertilize use, this strategy also prevents them from maximizing the return of investment in precision soil sampling. Each year, growers spend a lot of money in soil sampling and not using that information to its full potential means leaving money on the table or in this case more or so leaving it out in the field.

While this may have worked well or have had less impact on the overall profit in the past, the consequences of misapplications this year would be much greater when the fertilizer prices are two to three times higher than in previous years. Therefore, growers must plan accordingly in order to manage fertility in the most efficient manner. This is not the year to simply apply a set uniform rate in most of your fields, especially if already paying for grid or zone soil sampling and having a knowledge of areas in the field that need less or more fertilizer than that set uniform rate. Precision soil sampling combined with variable-rate application is much more efficient (by ensuring right rate at the right place) and cost effective than any uniform application method, and must be a part of grower’s nutrient management strategy in order better manage fertilizer costs this year.

Variable-rate technology has been around for almost a decade now; however, it’s starting to get lot more attention recently due to increasing input costs every year and emphasis on being more efficient and sustainable with inputs. Since its introduction, the variable-rate technology has also improved significantly over the years with most of the major equipment manufacturers and/or technology companies offering various variable-rate packages for both used and new fertilizer application equipment. Additionally, several low-cost and user-friendly tools as well as online applications are also available today for both growers and consultants to create sampling grids or management zones, import/analyze soil test results, and create variable-rate prescription maps – offering it a relatively easier and simpler workflow. So, whether a grower apply his own fertilizer or have custom applicator (e.g. co-op, fertilizer retailer, etc.) do it for him, there are multiple options available today to get started with variable-rate. Generally, the first step is to talk to your consultant, crop advisor or technology company to know where you are currently in the process – starting from precision soil sampling to current equipment capabilities to VR prescription map creation – and then how they can work with you in getting started with implementing variable-rate applications on your farm.

Few tips to consider before starting out or going all in with variable-rate applications:

  • Start out with few selected fields that are more non-uniform and have the greatest potential to benefit from variable-rate applications.
  • Use historical knowledge about the fields and management practices in combination with soil test results when delineating management zones.
  • Consider application equipment and technology limitations when delineating zones, especially size and transition between the zones
  • Keep management zones to a maximum of three or four for easier and effective implementation. More zones can make the process overwhelming and confusing.   
  • Consider fertilizer properties, especially shape, size and density, when creating and spreading different blends. Uneven distribution and segregation can cause application issues.  
  • Be patient with technology and the overall process especially during the first year. Things will get easier and better as time goes by and with VR applications in more fields.
  • At the end of each year, assess what went right, and what didn’t go as planned and why. This will help to continuously learn and improve the process as well as minimize any frustrations.

In summary, considering the situation with fertilizer prices this is not the year to cut corners on precision soil sampling or reduce application rates unknowingly in order to lower input costs but to effectively utilize tools and strategies such as precision soil sampling and variable-rate application to be more efficient and cost-effective to maximize the return on investments on your farm.

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