# Gypsum Requirement

> Gypsum Requirement (iPhone/iPad app by North Dakota State University.)

- Source: https://appshunter.io/ios/app/gypsum-requirement/id1299303426 (this page in markdown: same URL + `.md`)
- Developer: [North Dakota State University](https://appshunter.io/developer/493125863)
- Category: Productivity
- Price: Free
- Age rating: 4+
- Requires: iOS 10 · 13 MB
- Languages: American English
- Released: 2017-10-25
- Data updated: 2026-05-18
- User reviews in markdown: https://appshunter.io/ios/app/gypsum-requirement/id1299303426/reviews.md

## What is Gypsum Requirement?

There are over 70 million acres of naturally occurring sodic soils in the United States, and over 1.4 billion acres worldwide. Gypsum has been used as an amendment for over 100 years to improve the productivity of sodic soils. Gypsum does two things: 1) provides Ca2+ to displace Na+ from the soil’s exchange sites, and 2) maintains or increases the soil salinity.  Applying the correct amount of gypsum requires knowledge of soil parameters as well as the quality of the gypsum. By understanding what is required to calculate Gypsum Requirement will allow one to have the proper soil tests conducted so that the most accurate determination is made.

The Gypsum Requirement app can be used to answer the question “how much gypsum should I apply to my sodic soil?”  The calculator is based on the equation developed by North Dakota native Dr. James Oster and others. The app is easy to use and allows one to easily determine the Gypsum Requirement for sodic soils. 

Gypsum Requirement Main Features

Easily enter values for initial and final ESP or SAR, soil bulk density, depth needed to be treated, efficiency, gypsum purity, and cation exchange capacity.

Gypsum Requirement is reported in units of Mg/ha or tons/acre.


## Version history (last 3 releases)

### 1.2 — 2018-05-11

This app has been updated by Apple to display the Apple Watch app icon.

A minor error in the introduction section was corrected.

### 1.1 — 2018-01-20

A minor unit error in the app intro section was corrected.

### 1.0 — 2017-10-25

No release notes.

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All apps by North Dakota State University: https://appshunter.io/developer/493125863

## Related topics

[ghpso](https://appshunter.io/ios/topics/ghpso) · [bosum](https://appshunter.io/ios/topics/bosum)

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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 2026-05-18.*