Nutrient value of gypsum fertilizer

Written by arlene miles
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Nutrient value of gypsum fertilizer
Gypsum supplies calcium and sulphur and aids in the uptake of soil nutrients (herb garden image by Steve Lovegrove from

Gypsum, when used as a fertiliser, provides only two main nutrients--calcium and sulphur--in significant amounts to soil. The mineral’s main effect is to loosen compacted soil, thus improving nutrient uptake through root structure. Because of its inherent low nutrient value, other organic fertilisers, such as hummus, are recommended for use in conjunction with gypsum.

Calcium and Sulfur

The most common form of gypsum, which is a naturally occurring mineral, is calcium sulphate dihydrate, meaning two water molecules are associated with each single molecule of calcium sulphate. In its chemically pure form, gypsum contains 23.28 per cent calcium (Ca) and 18.62 per cent sulphur. Most gypsum sold for agricultural purposes has less of both nutrients, generally between 18 and 23 per cent for calcium and 15 and 19 per cent for sulphur.

Calcium Benefits

The availability of calcium in gypsum has marked benefits for fruit development. Because calcium moves slowly, it often is not transported in sufficient amounts from the roots to the end product, which is fruit. Gypsum aids in this transportation. It also helps below the soil surface to keep peanuts disease free, and prevents blossom-end root in watermelon and tomatoes, and bitter pit in apples. Root rot in avocado trees is also partially controlled by gypsum.

Other Nutrients

Although not a major supplier of other plant foods, gypsum does have some additional nutrients. According to Spectrum Analytic, natural gypsum is also composed of 1.3 per cent magnesium.

Several other nutrients are present in parts per million (ppm) concentrations. These include: boron, 9.4; Iron, 1045; maganese, 14.6; phosphorus, 30.6.


Because gypsum is highly soluble, it is particularly beneficial for acid-loving plants. Acidic soils are normally low in calcium, yet plants still need it for proper growth. Among the plants grown in acidic soil that benefit from the addition of gypsum are potatoes, blueberries and commercial Christmas trees.

Nutrient Uptake

The most notable benefit of gypsum is its ability to loosen compacted soil. This benefit indirectly affects the availability of nutrients located within soil. When soil is dense, plant roots have a difficult time extracting available food from it. Uptake improves thanks to the calcium in gypsum, which creates space within the soil. Hummus in the soil is able to integrate better, with its nutrients also becoming more available to plants. Thanks to gypsum, plants are able to access nitrogen, iron and zinc, especially when plant roots are young.

Gypsum is particularly effective in minimising nitrogen loss to the air by decreasing soil's pH levels and forming a complex calcium salt that binds to ammonium hydroxide.

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