# NPK Credits — Manure Nutrient Credits

> Calculates manure and legume nutrient credits for farmers to reduce fertilizer costs. (iPhone/iPad app by UW-Madison Integrated Pest Management program.)

- Source: https://appshunter.io/ios/app/npk-credits/id954888966 (this page in markdown: same URL + `.md`)
- Developer: [UW-Madison Integrated Pest Management program](https://appshunter.io/developer/455090091)
- Category: Utilities, Education
- Price: Free
- Rating: 5.00/5 from 1 App Store ratings · 1 written reviews indexed
- Age rating: 4+
- Requires: iOS 16.0 · 1 MB
- Languages: American English
- Released: 2015-01-11
- Data updated: 2026-06-10
- Monetization: free
- User reviews in markdown: https://appshunter.io/ios/app/npk-credits/id954888966/reviews.md

## What is NPK Credits?

Farmers can save money and protect the environment by taking credit for the fertilizer value of manure and legume crops. The value of these credits are subtracted from the base (unadjusted) fertilizer recommendations for a field. This reduces the money spent on purchased fertilizer applications and helps prevent over-application. There are formulas and math involved in determining the credit values. This app includes three calculators that have these formulas built in and do all the math for you. 

This app calculates the plant-available nitrogen (N), phosphorus (P2O5), potassium (K2O), and sulfur (S) nutrient credits (i.e. the fertilizer value) of manure from various livestock species that are applied to cropland fields. The app also calculates the N credit available to crops that follow forage legumes in the rotation. 


Analyzed Nutrient Content is used when the manure has been analyzed by a laboratory for its nutrient content. When using this part of the app, you can:

• Select the manure source (livestock species and liquid or solid form).
• Select one of the three categories for the time from application to 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 [- +] buttons to raise or lower the values.

Your calculated nutrient credits from this manure application are displayed at the bottom of the screen. These credits should be subtracted from the base (unadjusted) fertilizer recommendations for a field receiving this manure. If the total nutrient content is entered, the app will covert these values to available nutrient content automatically. Likewise, if the available nutrient content of the manure is entered, the equivalent total nutrient content of the manure sample will be displayed. Tap the Reset button in the center of the screen to clear the nutrient content displays.


Average Nutrient Content is used when the manure has not been analyzed by a laboratory for its nutrient content. When this is the case, the typical nutrient contents (also called book values) based on lab analysis averages will be used. When using this part of the app, you can:

• Select the manure source (livestock species and liquid or solid form).
• Select one of the three categories for the time from application to incorporation of the manure.
• Choose the manure application rate by tapping the [- +] buttons to raise or lower the values.

Your calculated nutrient credits from this manure application are displayed at the bottom of the screen. These credits should be subtracted from the base (unadjusted) fertilizer recommendations for a field receiving this manure. Manure nutrient content can vary greatly; manure analysis is encouraged.


Legume Nitrogen Credits is used when crops follow forage legumes in rotation.

When using this part of the app, you can:

• Select the forage legume crop (Alfalfa or Red Clover/Birdsfoot Trefoil).
• Select the soil texture of the field (Medium/Fine Soils or Sand).
• Select the density of the legume stand at the time of termination.
• Select the amount of plant regrowth present at the time the legume crop is killed.

The legume-N nutrient credit available to the crop that follows in the rotation is displayed at the bottom of the screen. This amount should be subtracted from the base (unadjusted) N fertilizer recommendation.

## Key features

- Manure nutrient credit calculation
- Legume nitrogen credit calculation
- Analyzed nutrient content input
- Average nutrient content input
- Automatic math for credit values
- Reduces purchased fertilizer costs

## Recent user reviews (1 of 1)

All indexed reviews: https://appshunter.io/ios/app/npk-credits/id954888966/reviews.md

### 1/5 — Rubbish

*2024-04-06*

Not sure why Apple allows this in the App Stor

## Frequently asked questions about NPK Credits

### What is NPK Credits?

NPK Credits is a utility app designed for farmers to calculate the fertilizer value of manure and legume crops. It helps reduce purchased fertilizer costs and prevent over-application by integrating these credits into field recommendations.

### How does NPK Credits calculate manure nutrient credits?

NPK Credits offers two methods: 'Analyzed Nutrient Content' where you input lab values, and 'Average Nutrient Content' using book values based on livestock species and manure form. It considers time from application to incorporation and application rate.

### Can NPK Credits calculate nitrogen credits from legumes?

Yes, NPK Credits has a dedicated section for 'Legume Nitrogen Credits'. You can select the forage legume crop, such as Alfalfa or Red Clover/Birdsfoot Trefoil, to determine the available nitrogen credit for subsequent crops.

### Does NPK Credits require an internet connection?

The provided data does not specify offline capabilities. However, as a calculation-heavy utility app, it is likely designed to function without an internet connection for core features.

### What devices support NPK Credits?

NPK Credits is available for iPhone and iPad devices, as indicated by the 'supportedDevices' field.

### How often is NPK Credits updated?

The app was last updated on August 8, 2023, with version 1.19. This suggests a relatively active development cycle for updates and improvements.

### Is NPK Credits suitable for all ages?

NPK Credits has an age rating of '4+', making it appropriate for a wide range of users, including younger individuals assisting with farm management tasks.

### What is the user sentiment for NPK Credits?

Based on the available data, NPK Credits has a perfect rating of '5.0 stars from 1 ratings', indicating highly positive user satisfaction.

## Version history (last 4 releases)

### 1.19 — 2023-08-08

Fixed an incorrect value for the legume credit calculator. 
Updated app info screen. Updated app for the newest phone models.

### 1.18 — 2022-12-27

Update for iOS 16, new UI design and other minor improvements.

### 1.1 — 2019-08-12

Changed navigation, added additional instructions to the help section.

### 1.0 — 2015-01-09

No release notes.

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*Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-06-10.*