Introduction to the Encirca® Fertility Service
Crop Insights by Andy Heggenstaller, Ph.D.¹ and Bob Gunzenhauser²
- Tools that combine soil test and yield data with science-based recommendations for determining variable rate fertilizer and lime applications offer the greatest potential for reducing fertility input costs without sacrificing yield.
- The Encirca® Fertility service is a new offering from DuPont Pioneer designed to help growers maximize return on P, K, and lime investments.
- The Encirca Fertility service incorporates grower data, Encirca Decision Zones, and university fertility recommendations to estimate nutrient needs and allocate fertilizer based upon potential return on fertilizer investment for each management zone in the field.
- Because variable rate applications based on the Encirca Fertility service integrate the agronomic and economic factors that drive profitability, prescriptions can be generated that optimize nutrient application rates for any fertility budget.
Soil Fertility in the Current Ag Economy
When crop production margins are narrow, many growers adjust their fertility program to reduce input costs. In these situations, nitrogen is often prioritized over other fertility inputs. While this approach makes sense when P, K, and other nutrient levels are in the optimum range, it can result in lost yield and profit when other fertility factors limit the crop from making full use of applied nitrogen. It is possible to maintain yields with lower fertility expenses but only when input reductions are based on sound soil fertility fundamentals.
Soil Fertility Fundamentals
Soil testing is the foundation of soil P, K, and lime management. Soil test levels provide an indication of the probability of a yield response to applied fertilizer based on university research. While the exact relationship between soil nutrient concentrations (in ppm) and soil test levels (low, optimum, high, etc.) varies by state, most fertility recommendation systems align to one degree or another with a "build-maintain-drawdown" strategy (Figure 1). Following this strategy, fertilizer is applied to very low and low testing soils at relatively high rates to build fertility and increase yields.
Figure 1. Generalized relationship between soil test levels, yield response probability, fertilizer need, and recommended fertility management strategy (adapted from Mallarino et al., 2013 and Vitosh et al., 1995).
Once soil test levels reach the critical level and are in the optimum range, fertilizer is applied at rates equal to crop removal at some frequency in order to maintain long-term soil fertility. Little or no fertilizer is applied to high and very high testing soils, where a drawdown of nutrients can take place with minimal risk of reduced yields in the short-term. Following a build-maintain-drawdown strategy, fertilizer can be withheld from higher testing field areas and redirected toward very low and low testing zones in a way that minimizes input costs while preserving most or all yield potential. Withholding fertilizer from optimum and high testing field areas is not a long-term strategy, however, as it will eventually result in depleted soil fertility and reduced yields. For this reason, frequent soil testing combined with variable rate application is the best approach for adapting fertility management to changing market conditions.
The Encirca® Fertility service
The Encirca® Fertility service is a new offering from DuPont Pioneer designed to help growers maximize return on their P, K, and lime investments under any market situation. At its core, the Encirca Fertility service combines yield and soil test data in order to allocate nutrients based upon the potential return on fertilizer investment for each management zone in a field. Using the service, growers can generate variable rate fertilizer prescriptions that best fit their budget based on zone-specific yield targets, yield history, soil test results, and their preferred state or custom recommendations. Key features of the Encirca Fertility service include:
Driven by Grower Data
The Encirca Fertility service starts with grower yield and soil data to establish the fertility needs in each field. Yield data can be transmitted seamlessly using most wireless data transfer services, including Encirca Sync Pro. Similarly, soil data can be automatically imported from most major soil test laboratories.
Built on Encirca Decision Zones
The Encirca Fertility service defines field productivity targets using Encirca Decision Zones, which are a composite of up to three spatial data layers (Figure 3A). All Decision Zones start with DuPont Pioneer’s improved soil maps, known as Environmental Response Units (ERUs) (Figure 3B). Environmental response units reclassify the spatial distribution of soil properties expressed in public soil maps using high-resolution digital elevation data. Because they more precisely account for topography, ERUs describe soil-derived differences in field productivity better than public soil maps (Bobryk et al., 2016).-
Where historical yield data are available, multi-year yield analysis is also used as a Decision Zone input (Figure 3C). Multi-year yield analysis combines three or more years of historical data to create a field map of relative productivity potential. A third layer can also be incorporated into Decision Zones, when necessary, to define field areas, such as irrigation pivot corners, that are managed for a different yield level than the remainder of a field (Figure 3D).
Aligned with University Fertility Recommendations
Many state universities have developed soil fertility recommendations specifically designed for use in their region. These recommendations are based on calculations established through years of field research. State recommendations vary from one another in numerous ways, including soil test methods, soil test level ranges, crop removal rates, and recommended application rates. Growers using the Encirca Fertility service can select their preferred state calculator or set-up a custom calculator to use as the basis for their soil fertility program.
Powered by Encirca® services Analytics
The Encirca® Fertility service uses a model to determine nutrient needs based on the productivity targets for each Decision Zone in a field and the corresponding interpolated soil test level (Figure 4). Calculated nutrient needs will be highest for field areas with low soil test levels, as these field areas offer the greatest financial return on applied fertilizer. In the optimum soil test range, nutrient needs will vary according to productivity targets, which indicate expected crop nutrient removal rates. Specific nutrient quantities will align with the state or custom fertility calculator selected by the user.
Flexible Fertility Prescriptions
Once nutrient needs are calculated by the Encirca Fertility service, users can generate variable rate fertilizer or lime prescription files using one of two approaches. If the user’s objective is to optimize return on fertility investment with no budget constraints, they simply select a fertilizer or lime product from their custom list and apply it to the nutrient needs for a specified field (Figure 5A). In this case, the application prescription will match exactly with the field’s nutrient needs but expressed in units of the specified fertilizer or lime product (Figure 5B).
For users making fertility investment decisions on a defined budget, the Encirca Yield Fertility service offers a unique feature called Opti-Allocate. To create fertilizer prescriptions that maximize return on investment for a specific but limited fertilizer expenditure, users enter their desired budget level, and the best recommendation for that budget will be automatically generated (Figure 5C).
Figure 5. Calculated P and K needs (A), optimum fertilizer recommendation (B), and best fertilizer recommendation if fertility budget is limited (C) for a field enrolled in the Encirca Fertility service.
Unlike other variable rate fertility programs, the Opti-Allocate feature does not cut application rates evenly across the field when the available fertilizer budget is less than the optimum recommendation. Rather, Opti-Allocate iteratively assigns fertilizer inputs to the field area with the greatest potential return on fertilizer investment until the available fertility budget is exhausted (Figure 6).
Figure 6. Diagrammatic representation of the fertility return on investment (ROI) model used by the Encirca® Fertility service to prioritize nutrient inputs based on productivity targets and soil test levels.
Balanced Data Interpolation
All variable rate fertility recommendations that use soil sample data incorporate some process to interpolate between sampled field positions. Many variable rate recommendations linearly extrapolate between sampled points, which results in inaccurate interpolation and large changes in application rates across small distances. The Encirca Fertility service employs an optimal smoothing model that maximizes overall accuracy and better matches application capabilities (Figure 7).
Figure 7. Comparison of sample, interpolation, and total accuracy for three soil sample interpolation models. The Encirca Fertility service employs an optimal smoothing model that maximizes overall accuracy.
Convenient Field Grouping
While fields have varying fertility needs, similar products and management strategies are often applied to groups of fields that share common attributes, such as land tenure, location, or management history. The Encirca Fertility service allows users to arrange fields into groups to which common management can be applied.
Local Encirca Certified Services Agent
The Encirca Fertility service includes direct, in-field support from an Encirca certified services agent who works side-by-side with growers to ensure that management decisions are tailored to the unique context of their individual farming operation.
The Encirca Fertility service is a new offering from DuPont Pioneer designed to help growers maximize return on P, K, and lime investments. The Fertility service incorporates grower data, Encirca Decision Zones, and university fertility recommendations to estimate nutrient needs and allocate fertilizer based upon potential return on fertilizer investment for each management zone in the field. For growers managing fertility on a tight budget, a unique feature called Opti-Allocate can be used to create fertilizer prescriptions that maximize return on investment for a specific but limited fertilizer expenditure. In conjunction with an Encirca certified service agent, the Encirca Fertility service offers a powerful, flexible solution for soil fertility management. Because Encirca services variable rate applications integrate the agronomic and economic factors that drive profitability, prescriptions can be generated that optimize application rates for any fertility budget.
Bobryk, C.W., D.B. Meyers, N.R. Kitchen, J.F. Shanahan, K.A. Sudduth, S.T. Drummond, B. Gunzenhauser, and N. N. Gomez Raboteaux. 2016. Validating a digital soil map with corn yield data for precision agriculture decision support. Agronomy Journal. 108:3.
Mallarino, A.P., J.E. Sawyer, and S.K. Barnhart. 2013. A general guide for crop nutrient and limestone recommendations in Iowa. Extension Bulletin PM 1688. Iowa State University, Ames, IA.
Vitosh, M.L., J.W. Johnson, and D Mengel. 1995. Tri-state fertilizer recommendations for corn, soybeans, wheat and alfalfa. Extension Bulletin E-2567. Purdue University, West Lafayette, IN.
¹ Agronomy Research Manager, DuPont Pioneer
² Manager, Technical Services, Encirca Services, DuPont Pioneer