University of Wisconsin Integrated Pest Management Apps
NPK Credits Calculator 1.0
Farmers can save money and protect theenvironment by taking credit for the fertilizer value of manure andlegume crops. The value of these credits are subtracted from thebase (unadjusted) fertilizer recommendations for a field. Thisreduces the money spent on purchased fertilizer applications andhelps prevent over-application. There are formulas and mathinvolved in determining the credit values. This app includes threecalculators that have these formulas built in and do all the mathfor you.This app calculates the plant-available nitrogen (N), phosphorus(P2O5), potassium (K2O), and sulfur (S) nutrient credits (i.e. thefertilizer value) of manure from various livestock species that areapplied to cropland fields. The app also calculates the N creditavailable to crops that follow forage legumes in the rotation.Analyzed Nutrient Content is used when the manure has been analyzedby a laboratory for its nutrient content. When using this part ofthe app, you can:• Select the manure source (livestock species and liquid orsolid form).• Select one of the three categories for the time from applicationto incorporation of the manure.• Enter the reported lab values for either total or available N,P2O5, K2O, and S from the lab report.• Choose the manure application rate by tapping the [- +] buttonsto raise or lower the values.Your calculated nutrient credits from this manure applicationare displayed at the bottom of the screen. These credits should besubtracted from the base (unadjusted) fertilizer recommendationsfor a field receiving this manure. If the total nutrient content isentered, the app will covert these values to available nutrientcontent automatically. Likewise, if the available nutrient contentof the manure is entered, the equivalent total nutrient content ofthe manure sample will be displayed. Tap the Reset button in thecenter of the screen to clear the nutrient content displays.Average Nutrient Content is used when the manure has not beenanalyzed by a laboratory for its nutrient content. When this is thecase, the typical nutrient contents (also called book values) basedon lab analysis averages will be used. When using this part of theapp, you can:• Select the manure source (livestock species and liquid orsolid form).• Select one of the three categories for the time from applicationto incorporation of the manure.• Choose the manure application rate by tapping the [- +] buttonsto raise or lower the values.Your calculated nutrient credits from this manure applicationare displayed at the bottom of the screen. These credits should besubtracted from the base (unadjusted) fertilizer recommendationsfor a field receiving this manure. Manure nutrient content can varygreatly; manure analysis is encouraged.Legume Nitrogen Credits is used when crops follow forage legumes inrotation.When using this part of the app, you can:• Select the forage legume crop (Alfalfa or Red Clover/BirdsfootTrefoil).• Select the soil texture of the field (Medium/Fine Soils orSand).• Select the density of the legume stand at the time oftermination.• Select the amount of plant regrowth present at the time thelegume crop is killed.The legume-N nutrient credit available to the crop that followsin the rotation is displayed at the bottom of the screen. Thisamount should be subtracted from the base (unadjusted) N fertilizerrecommendation.
Corn N Rate Calculator 1.2.1
This app is designed to assist producers inselecting a nitrogen (N) rate that improves profitability whennitrogen and corn prices fluctuate. Maximum return to N (MRTN) isthe N rate that will be most profitable for a particular N:Cornprice ratio. The MRTN rate is the large number expressed in lbsN/acre at the bottom of the screen, and is the total N raterecommended for your field. From this number, you need to subtractthe lbs N/acre starter you apply and subtract the lbs N/acre Ncredits you take. Below the single large number is the range of Nrates that result in profitability within $1/acre of the MRTNrate.
