To further understand the nitrogen recommendation and view detailed statistics on each zone in the field you can click an individual grid cell or zone then click "view details".
The following page will be displayed:
Here you will see a number of details about that specific zone in the field.
Sidedress N Recommendation is calculated by Adapt-N using the following equation:
"Expected N in crop at Harvest" - "N in crop now" - "N in soil now" - "Future Net N credits" - "Partial N credit from soybean" + "Expected future fertilizer loss" - "Profit Factor"
Explanation of Terms
Expected N in crop at harvest is the amount of N estimated to be in the corn crop at harvest time. This is calculated from the "Expected Yield" input combined with the Recommendation Parameter for Pounds of N per Expected Bushel of Yield. Estimates of N contents of grain, stover and roots are used.
N mineralization so far is plant-available N derived from soil organic matter or organic amendments from simulation start date until the current date.
N loss since planting / since simulation start date reflects all nitrogen losses since the beginning of the simulation or since the planting date. This includes all nitrogen lost from manure applications, overwinter leaching losses, lost nitrogen from organic matter mineralization, as well as losses from all types of N applications (ammonia volatilization, etc.).
Additional N Credits includes credits from previous crops as well as from manure applications. This is supplemental to the simulated effects of N mineralization or immobilization from incorporation of previous-crop residues.
N in crop now is the amount of N that is already in the crop for the day you run the model (or on the season end date you selected if you are running on a prior season). This is determined by simulations using the corn growth routines in the model, and incorporates information from the high resolution weather data and soil N availability for the field location.
Expected Future Fertilizer Loss represents the N loss risk specifically for the recommended fertilizer application. This basically is a time-dependent fertilizer use efficiency factor. Values represent the fraction of the fertilizer to be applied that can be expected to be lost due to weather events following application, based on probabilistic estimates from 30 year simulations. Values are proportional to the recommended fertilizer rate, and they will generally decrease as the growing season progresses and the risk of N losses from weather events is reduced
Future Net N Credits represents the combined nitrogen credits and debits that are expected for the remainder of the growing season. Credits include future mineralization from soil organic matter, manure applications, previous crop, etc. They are generally higher with soils with high organic matter contents and when organic amendments have been applied. Debits include the risks associated with future leaching and denitrification losses, which are mostly based on current nitrate levels in the soil, potential future mineralized N, and the time in the growing season. In general, debits from future losses are greater for simulations done in early spring, as the N loss risk from high rainfall events in the following weeks is higher. Also, debits are higher for cases where high N rates have been applied prior to planting, as this generates greater potential for early-season losses. As the growing season progresses and weather events are playing out, the recommendations become more precise and the N loss risk is reduced. Values are probabilistic and based on 30 year simulations.
N in soil now is the amount of mineral N available to the crop from the soil for the day you run the model. This is determined from model simulations based on input information on soil type, rooting depth, slope, organic matter content, tillage system, previous organic and inorganic N applications, rotations (sod, soybean, etc.), and corn variety, maturity class, and population, where mineralization and losses are similarly affected by weather to date.
Rainfall since planting / since simulation start date reflects climate data which is updated several times per day. (estimates may slightly change in following 2 days as more precise precipitation data become available).
Current Nitrate / Virtual PSNT represent simulated nitrate levels in the top 12” of the soil on a daily basis throughout the season. The virtual PSNT is presented as a convenient comparison but is not used directly to make a recommendation. Our field trial data show the virtual PSNT simulated by Adapt-N to generally be within 5 ppm of the measured value. See this article for further details and recommended sampling protocol.
Profit Factor is a correction factor to optimize profits to N application from the combined effects of the fertilizer-to-grain price ratio and the uncertainty of Adapt-N predictions. The price ratio correction accounts for the cost of fertilizer relative to the returns from additional yield with higher N inputs. This results in lower recommended N rates with more expensive fertilizer or lower corn grain prices. The uncertainty correction accounts for the fact that nonlinear yield response to N inputs entails a greater profit penalty (risk) for under-prediction than over-prediction of the optimum N rate, and therefore the need for an adjustment of the recommended N rate. In all, the Profit Factor is adjusted based on (i) the price of fertilizer, (ii) the price of corn (grain, silage, or sweet), and (iii) the primary N source (manure or fertilizer). View this article for information on how to modify these parameters.
The Sidedress N Recommendation is therefore the difference between net N availability (a function of N inputs, weather-affected mineral N gains and losses, and management) and the final expected N content of the crop. This difference needs to be made up by sidedressing to achieve full yield. The Adapt-N model does not include estimates of atmospheric N deposition as it makes a very minor contribution to corn N needs.