What Is the Formula Library?

Creating fertilizer prescriptions is made easy using VRAFY in John Deere Operations Center. When you are viewing your soil test results you can click on the “Create Formula Rx” text to get started creating your own prescriptions. There are a variety of formulas you can specialize to your farm’s needs. Each formula is able to read an Olsen, Bray or Mehlich 3 soil test.

01 pH Balance- the first formula group is useful to correct your pH. You can enter your ECCE from your available lime source to tailor the prescription to you. ECCE means an effective calcium carbonate equivalent where most lime sources depending on your state it is reported in lbs/ton or percentage of calcium. This can be edited in your Vars tab. There are six formulas where you can choose your pH 6.0, 6.5, or 6.9 depending on your crop needs. Those formulas are calculated off your Buffer pH and pH. If you are looking to correct your Calcium you can use “Target Ca Base Sat by Ca %” where you enter your percent calcium source and your desired base saturation target in the Vars tab to raise your Calcium. If your pH is too elevated, you can use AMS or Elemental Sulfur formulas to lower your soil pH. The K-Mag formula allows you to raise your Magnesium to balance your Calcium.

02 Crop Removal +- This section is great for maintaining your soil levels once they are built up or replace nutrients on rented ground. The system reads your yield map and produces a crop removal map from the field. You can adjust this map by utilizing the “yield adjustment %” variable on the vars tab so you could replace 125% of your yield instead of just 100%.

03 Crop Removal + Build- These formulas are a great combo product of building your soil test results and replacing the nutrients the crop has taken off. Using the “Vars” tab you choose your yield adjustment, choose a target ppm, your blend percent of the targeted nutrient, tons per acre of stover, and your build years. These formulas are running off your soil test levels and your yield map. If there is a point with extreme excess in a nutrient it will allow you to mine that given point down, so you are not over applying in an area where your nutrients are ample. This ensures your fertilizer dollars are best used.

04 Soil Only- P & K Builds- These formulas are specifically for building your soil levels to your desired levels. You can choose to build using a blend or straight potash or phosphorus sources. In the Vars tab you can edit the given target parts per million and target base saturation to fit your budget and soil needs. These prescriptions can read mehlich3, Olsen, and Bray soil sample tests.

05 Manure-Using VRAFY you can create a corn crop removal prescription based off your manure analysis. When you are using this formula there are default values for nutrient analysis so you will have to enter in your specific values. There are manure formulas for dry and liquid manure and corn grain and silage.

06 Zinc and Sulfur – Zinc is an important nutrient for your crop. There are two formulas to balance soil Zn levels. Based on Mulder’s chart there is antagonism with zinc and phosphorus. Ideally, we want your zinc to phosphorus ratio to be 1:10. You can choose “Balance Zn/Phos” to balance your zinc ppm to your phosphorus levels, please note there is a 25lb application max on zinc formulas. On the custom zinc formula, you can specify what parts per million you would like to build soil zinc levels to. For your Sulfur needs we can apply AMS or Elemental Sulfur. Sulfur is a leachable nutrient so excess water can lower the sulfur content or in poorly drained fields will have excess sulfur. Raising your sulfur will help with plant nutrient uptake.

07 Micronutrients- Micronutrients fall in the same line as zinc. The ideal ratios are 1:100 Boron to Calcium, 1:2 Copper to Zinc, and raising your Iron above your Manganese 2:1. There are formulas for each ratio that calculates using your soil test. If you are aiming for a certain part per million those are also available under micronutrients. You can denote that under the Vars tab. There is a limit of 4 ppm boron to protect your crop against boron toxicity and most micronutrient formulas have a set maximum application. On micronutrient formulas it is set to default as a switch rate application so results between 0-5 get 5 pounds and 5-10 get 10 pounds. This helps the machine handle lower application rates.

08 Nitrogen by Potential- There are a variety of Nitrogen formulas. Three anhydrous formulas run off soil results. If you go to the Vars tab you can enter your yield goal and adjust yield percentage. These formulas give you credit for Soil OM and NO3N from recent soil tests. The difference between these three is the output units in gal/ac, units of N/ac, or lbs./acre. There are three Urea formulas, one crediting NO3N and another that does not if you are missing that in your soil test. On the third one under the Vars tab you can adjust your N use efficiency although it auto defaults to 0.8# of Nitrogen per bushel. If you want to enter in your yield goal you can click flat and type in your yield goal under “Value/Seasons”.

09 Seeding – There are two seeding prescriptions offered at the plus level. The corn seeding recommendation utilizes previous yield map(s). On the Vars tab you can select multiple years of yield data where it will take the average yield or select one single year that is a well presentation of the field. For each field you need to select a minimum and a maximum population. It will read the yield results and min. and max. to create a prescription using standard deviations. The soybean prescription reads yield map(s) and after you define the maximum and minimum it varies the rate based off standard deviation. In high yielding areas you plant less soybeans whereas in corn it would have a higher population.

There are also autogenerated crop removal formulas through VRAFY Basic that will show up once your yield layer is finished. If you have any further questions about a formula or its purpose, contact us.