The HI3896-025 are high quality reagents that are pre-measured, allowing for users to achieve fast and accurate measurements of nitrogen, phosphorus, pH, and potassium with the soil test kit. This replacement set includes enough reagents for approximately 25 tests for each of the four measured parameters.

The nitrogen, phosphorus, and pH tests are colorimetric tests. During the tests, a color is developed which corresponds with the fertility of the soil. To determine the fertility, the color developed has to be compared with one of the supplied color cards.

The reagents for nitrogen follow the Ned method to determine concentration as nitrate-nitrogen (NO3--N). These reagents are designed to be used with samples to generally indicate the nitrogen amount in trace, low, medium, and high quantities.

The reagents for phosphorus follow the ascorbic acid method to determine concentration as phosphorus pentoxide (P2O5). These reagents are designed to be used with samples to generally indicate the phosphorus amount in trace, low, medium, and high quantities.

The reagents for pH follow the colorimetric indicator method to determine soil pH. These reagents are designed to be used with samples that have an expected pH range of 4 to 9 pH.

The potassium (K2O) test is a turbidimetric test. If potassium is present in a soil sample, turbidity is formed. A blue color will also develop to help in reading the test result. To determine the amount of potassium present, the color developed has to be compared with the supplied color card.

The reagents for potassium follow the tetraphenylborate method to determine concentration as potassium oxide (K2O). These reagents are designed to be used with samples to generally indicate the potassium amount in trace, low, medium, and high quantities.