One of the concerns today is that soils are being degraded by intensive agricultural production, salinity or contamination. Soil degradation can be generally defined as a decline in soil quality caused by its improper and unsustainable use.
Soil degradation is slowly becoming a serious global problem and is exacerbated by climate change and the rise in global food demands. Degradation encompasses deterioration of physical, chemical and biological processes. Soil is one of our most important natural resources. Keeping our soils healthy is essential for food production and for providing a safe and adequate water supply over the long term.
The good news is that soil degradation can be reversed and remediated. The process for remediation is dependent on the primary cause of degradation. Gypsum, or calcium sulfate can help play a role in many scenarios.
Salinity and Sodic Soils: Soil salinity is the salt content in the soil where salts are the soluble nutrient ions in the soil solution (and not on the soil’s cation exchange complex). Sodic soils are characterized by excessive amounts of exchangeable sodium on the soil’s exchange complex. Applying gypsum and leaching with irrigation water reclaims saline soils. Gypsum plays an important role in improving soil structural properties so that leaching can effectively remove salts, particularly sodium, out of the root zone. The calcium also displaces the sodium held on the clay-binding sites so it can be displaced.
Degraded Soil Structure: Applying gypsum as s soil amendment vastly improves soil structure. The calcium in gypsum helps flocculate or aid particle aggregation in soil. Intensive tillage and crop management tends to disperse clay particles and causes a collapse of soil structure. This reduces porosity, aeration, drainage, root growth, and microbial and arthropod activity in the soil. Gypsum is used to improve aggregation and overcome natural clay dispersion, ultimately improving soil tilth and health.
Contaminated Soils: Soils can be contaminated by heavy metals from sludge or by carbon-based pesticides and petroleum products. Most carbon-based pollutants will degrade vital soil microorganisms. Gypsum can improve soil health and structure by creating a more optimal environment for microbial activity, leading to the remediation or removal of contaminates.
Remediates Aluminum Toxicity: In acid soils, pH 5.5 or less, aluminum becomes more soluble and toxic to roots. Gypsum can improve some acid soils even beyond what lime alone can achieve. Gypsum is soluble and leaches down into the subsoil and improves root growth to counter the impacts of aluminum.
Reductions in Erosion: Soil lost to erosion can take decades to replace. A number of soil conservation practices limit soil losses. However the addition of gypsum improves soil aggregation and porosity, improving water infiltration and hold capacity. This means less water and soil runoff and ultimately, less erosion that naturally carries soil particles, nutrients and pesticides into surface waters. Gypsum should be considered a Best Management Practice for reducing soluble nitrogen and phosphorus losses.
Increases in Water Infiltration: Gypsum improves the ability of soil to drain adequately and to not become waterlogged due to a combination of high sodium, swelling clay and excessive water.
Declining Natural Fertility: Gypsum is a source of calcium and sulfur for plant and microbial nutrition. There is less sulfur deposition from the atmosphere and crops are showing more sulfur deficiency. Gypsum is a source of sulfur for plant nutrition and calcium is essential for most nutrients to be absorbed by plants roots. Without adequate soluble calcium nutrient uptake mechanisms would fail.
Dr. Davidson posts articles on soil health and management related subjects. If you have suggestions for topics or questions, feel free to contact him at firstname.lastname@example.org or call 402-649-5919