Low-rate Application of Pelleted Lime

Soil pH is a measure of soil acidity and is one of the most important chemical characteristics of a soil, impacting soil and plant health. When soil pH is below optimal for a crop, bulk agricultural lime is the best option for increasing soil pH. Sometimes truck load lime by the ton is not an option due to lack of local supply or small production scale. When this is the case, the use of pelleted lime may be a good option. Pelleted lime is much more expensive than bulk agricultural lime, and lower rates are needed to reduce cost.

WVU Extension lime recommendations are based on soil pH measured in water, soil pH measured in a standard buffer solution and the soil pH required by the crop listed on the sample submission form. For crops needing a soil pH of 6.5 or above, such as alfalfa, the buffer pH is used to calculate the lime requirement with a maximum lime recommendation of 3 tons per acre. For crops not needing a soil pH of 6.5, the lime recommendation is 2 tons per acre when the soil pH is below 6.0. This 2-ton rate is used since most spreader trucks are not able to reliably spread finely ground, high quality lime at rates lower than 2-tons per acre. Most fruit, vegetable, forage and agronomic crops grow best in a soil pH at or above 6.0.

All lime recommendations are based on using 100% effective neutralizing value (ENV) lime. The lime’s ENV is a measure of the ability of the lime to neutralize a soil’s pH and is based on the total neutralizing value (TNV) of the lime as calcium carbonate equivalence (CCE) and the fineness of the lime. These qualities are determined by the source and processing of the lime and are listed on the lime’s product label. The ENV of a given lime product can be calculated using the WVU Extension Ag Limestone Tool found at:

Standard lime recommendations are based on crops being planted on tilled soil and adjusting soil pH to an 8-inch soil depth. For permanent sod crops, such as pasture and long-term hay fields, the 2-ton liming rate is based on a 2-inch soil sample depth and field research conducted by Dr. Bill Bryan at WVU.

For high value crops grown in the field or high tunnels, such as fruit or vegetable crops, use the laboratory report recommended rate of lime. When cash flow limits inputs, use half the recommended rate, then soil test on an annual basis to monitor soil pH status and apply more lime as needed.

When application of bulk agricultural lime is not an option, the use of pelleted lime may be justified. Due to the high cost of pelleted lime, lower application rates of pelleted lime are needed to keep cost affordable. Therefore, there is a need for estimating how little pelleted lime is required for good crop production. The standard lime recommendation prior to 2020 was for raising the soil pH to 6.5 to an 8-inch plowed depth. For crops not grown on tilled soils and not needing a soil pH at 6.5, this was modified to a lime recommendation that would raise soil pH to 6.0 or greater to a 2-inch soil depth. This goal was to adjust soil pH in the top 2-inches of soil, where cool-season grasses and clovers have the bulk of their roots and most of the summer rainfall is captured and used. After adjusting recommendations to a soil pH of 6.0 and a 2-inch soil depth, the tons of 100% ENV lime needed is greatly reduced (Table 1).

Table 1. For a given soil pH, we calculate the lime required (LR, tons per acre) to adjust an average soil to a pH 6.0 to an 8-inch depth. The lime required to adjust the soil pH to 6.0 to a 2-inch depth was found by dividing this value by four. Practical pelleted lime application rates are rounded to the nearest 0.05 tons per acre. For soils having a pH below 5.5, apply 0.25 tons per acre and sample the field annually, applying another 0.25 tons as needed.

When managing crops on low pH soils (soil pH below 6.0) the priority is to grow crops that tolerant low soil pH (grasses and clovers) or need low soil pH (blueberries). There are four pH levels that are major markers for crop and liming management. These pH values are 5.5, 6.0, 6.5 and 7.0. When soil pH drops below 5.5, aluminum becomes more soluble in the soil water. Available aluminum ties up phosphorous and can become toxic to plants and soil health. These problems are offset to some degree by high soil organic matter and free calcium in the soil. Calcium sulfate can reduce aluminum availability without raising soil pH. Between a soil pH of 5.5 and 6.0, aluminum and manganese solubility are low, and many plants and bacteria begin to do well.

For example, grass-clover fields produce 85% to 90% of potential yield within this pH range when soil test phosphorus and potassium are near optimum. Above a soil pH of 6.0, most crops and soil bacteria do well, and major and minor minerals are readily available to plants. Some crops (alfalfa) require a soil pH at 6.5 or greater. As soil pH increases over 7.0, minor mineral availability decreases and their lack can adversely impact plant health.

Sustainable farming practices include environmental, economic and social considerations. Liming to correct low soil pH is a management practice that improves the soil environment for beneficial bacteria, fungus and plants. It also is an economic issue when lime is expensive. Under these economic conditions, apply low rates of lime over time to move soil pH up to 6.0 and grow crops adapted to lower soil pH. High quality pelleted lime will be labeled close to 100% calcium carbonate equivalent (CCE) and have 100% of the lime passing a 20-mesh screen.

Authors: Ed Rayburn, WVU Extension Professor Emeritus, and Bruce Loyd, WVU Extension Agent – Lewis County

Last Reviewed: July 2024

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