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Utilizing Lime and Gypsum in Organic Production

Sponsored by The Andersons

With the growing season nearing harvest, it is time to think about fall fertilizer applications, particularly for pH and liming needs. The first step is to take a thorough soil test to measure values of major nutrients (NPK), cations (calcium, magnesium, potassium, hydrogen, and sodium), and micronutrients. Depending on the soil test results, fall is an ideal time for the application of lime or gypsum as these mined sources break down in the soil over the winter to become readily available to the growing crop the following season.

Soil pH, Lime, and Gypsum 101

Soil pH is the measure of the concentration of hydrogen ions in the soil. The pH of soil affects the crop from planting to harvest because it determines the availability of nutrients through chemistry and microbial processes. Figure 1 shows how pH can influence nutrient uptake versus tie-up. It is ideal to maintain a soil pH between 5.8 and 6.8, where nutrients are most available. It is best practice to continually maintain soil pH, rather than wait for an imbalance to occur.

Figure 1: Chart displaying nutrient availability dependent on soil pH.
Figure 1: Chart displaying nutrient availability dependent on soil pH.

Lime delivers calcium and/or magnesium to the soil and raises pH. Nitrogen fertilizers acidify soil (lower pH), and if pH is low, lime will need to be applied. The issue with many ag limestone products is that they take time (usually two years) to significantly raise a pH deficiency into an optimal range. Adjustment of soil pH in-season is possible when using a pelletized limestone product. If soils are limed regularly, this will counteract the acidifying effect of nitrogen applications, and pH should never get too low.

Gypsum contains calcium and sulfur and is pH neutral. Gypsum also offers many benefits for improving soil structure in tight, compacted, or high-clay soils. The sulfur in gypsum attaches to magnesium cations that strongly bind soil particles closely together. The sulfur then flushes magnesium through the soil profile, helping to loosen soil. Over time, soil pore space is increased, allowing for greater water and air infiltration within the soil profile.

What’s the Gypsum Buzz?

Gypsum is a hot topic in agriculture these days. It is important to understand the differences between lime and gypsum, and even though gypsum is pricier than lime, gypsum should be applied at times when it is more appropriate. Unlike lime, gypsum provides needed sulfur to the soil. As a result of the Clean Air Act in 1963, crops do not receive sulfur in the form of acid rain because the rain is no longer acidic. Sulfur is an anion that is leachable in the soil profile, so it is up to growers to monitor sulfur levels and supplement as needed.

Sponsor Message

The Andersons Pelletize Products

The Andersons pelletized lime and gypsum products are a marriage of important attributes. You get high quality, mined calcium and either magnesium or sulfur, depending on the product, in a granule form that is user-friendly and spreads easily.

It is important to be thinking ahead to the next growing season now. Planning will put you in the most prepared position when it comes to the application of soil amendments to your fields. NutraSoft OP and NutraLime OP offer many soil health benefits, as well as critical nutrients.

View more information about The Andersons organic products on their website, https://andersonsplantnutrient.com/organics.