Liming Effects on Forage Sustainability and Economics
Funded by the Rangeland Sustainability Program (Government of Alberta)
In Alberta, more than 1 million acres of farmland are strongly acidic, with a pH of less than 5.5, and about 4.5 million acres are moderately acidic with a pH of 5.6 to 6.0 (GoA, 2004). Soil acidity is a significant and growing threat to forage production in Western Canada, particularly in the Peace River region. As soil pH drops below 6.0, and especially below 5.5, the productivity of key forage crops, particularly alfalfa and other legumes, can be greatly reduced. In general, liming is recommended for all strongly acidic soils and for many moderately acidic soils to boost and sustain crop productivity and create favourable conditions for beneficial microbes. Liming acidic soils raises pH to 6.0-7.0. It improves phosphorus availability and nitrogen fixation, with studies showing 20–30% higher forage yields (NSCA, 2025). This project, initiated in 2024, aims to determine the impact of various liming products on a legume-dominated pasture and to assess the economic benefits of lime use over three years.
What We Did
The trial was conducted on a producer’s pastureland near Sexsmith, AB (Legal Land Description: SE 3-74-6 W6). Pre-trial soil samples were collected in early spring of 2024 and sent to A&L Labs (London, Ontario) for analysis to determine soil pH and the suitability of the site for the trial. The soil reports showed a pH of 5.8 and calcium base saturation (Ca BS) of 42.9%, meeting the criteria for liming, which required a pH below 6.0 and Ca BS below 60%. The trial was set up as a randomized block design in 10 x 50 m strips, replicated three times, with similar-sized buffer strips separating treatments to prevent cross-contamination of lime products and to maintain the integrity of each treatment’s effects on soil and plant responses. The following treatments were applied (as a one-off) to strips:
Control or Check (no lime).
Pelletized lime (Standard 98G - 94% CaCO3 equivalent, Calcium Products, IA, USA) applied at 400 lbs/ac with a lime spreader equipped with vertical beaters and a spinning disc with a pass width of 2.5 m to ensure central band of 5.0 m from which soil and forage samples could be collected and observations made.
Ag lime (Ag Lime - 98% CaCO3 equivalent, supplied by Lime Stone Cowboys, Chetwynd, BC) applied at 4.56 tons/ac and also with a lime spreader equipped with vertical beaters and a spinning disc with a pass width of 2.5 m to ensure central band of 5.0 m from which soil and forage samples could be collected and observations made.
Wood ash (61% CaCO3 equivalent, a liming alternative obtained from a local mill) applied at 15 tons/ac using a burning manure spreader with a spinning disc to ensure a central bandwidth of 5.0 m from where samples will be collected.
The rate of application for each liming product was calculated to deliver equal quantities of calcium across all 3 liming treatments, based on their calcium carbonate equivalents, moisture content, and particle size. Baseline soil data was collected in 2024, prior to the implementation of liming treatments, with follow-up sampling conducted in 2025. Data was obtained from 3 georeferenced points per strip and included measurements of soil physical properties (bulk density, water infiltration, compaction, soil temperature, and volumetric water content) and soil chemical and biological properties assessed through laboratory analysis of bulked soil cores per strip. Legume nodulation was assessed on alfalfa plants. Forage clippings were also collected for botanical composition and forage dry matter (DM) determination at the early flowering stage, with subsamples sent to A&L Lab (London, Ontario), for forage quality analysis.
Results
Soil physical properties
Results obtained for various soil physical indicators for 2024 and 2025 are shown in Table 1.
Across all measured parameters—including infiltration, soil compaction, soil moisture at both depths, and bulk density—no significant differences were observed among treatments in either year, indicating that liming had no measurable effect on these soil physical properties over the study period. A general increase in soil infiltration was observed across the three liming treatments from 2024 to 2025, with ag lime exhibiting the greatest improvement, rising markedly from 2.4 to 6.4 in/hr. With soil compaction readings of 300 psi (pounds per square inch) across all treatments both before and after liming, it is evident that the paddock is highly compacted and that liming has not yet resulted in any measurable improvement in soil compaction.
Soil chemical properties
Table 2 shows soil chemical properties in both years.
Soil organic matter (OM): No significant differences were observed between treatments for OM after 1 year of liming product application. However, there was a trend toward increased OM from 2024 to 2025.
Soil pH: One year after liming, soil pH did not differ significantly among treatments.
Soil Ca: Soil calcium levels increased in all treatments from 2024 to 2025, with wood ash showing the largest increase (23%).
Other soil chemical indicators (CEC, K, Mg, NO3N, ENR, and KMG): No significant differences between treatments over the two years were noted for these soil indicators.
Plant tissue analysis
Plant tissue analysis provides a snapshot of a plant's nutrient status at the time of sampling, and this, in turn, shows whether soil nutrient supplies are adequate. Results of plant tissue analysis conducted on clippings taken from strips after 1 year of liming product application are shown in Table 3. There were no significant differences among treatments for any indicators, and values fell within the alfalfa book value ranges (Flynn et al., 1999) at the early bloom stage.
Legume nodulation
Alfalfa plants and roots were visually assessed for vigour, nodulation, and nitrogen fixation in 2024 and 2025. Plants were generally slightly chlorotic (yellow) and showed no visible nodules across all treatments.
Forage DM yield and botanical composition
In 2025, due to drought and feed shortages across the Peace region, the producer had to graze the first cut before samples could be taken. As a result, forage yield data are based on second-cut samples only, which were collected about 7 weeks after grazing.
From 2024 to 2025, second-cut forage yields generally improved (Table 4). The pelletized lime and wood ash treatments showed the biggest gains, with forage dry matter yields increasing by 46% and 40%, respectively. The ag lime treatment increased yields by 14%. The control was the only treatment in which yields decreased by about 12.5%.
The plant mix in the pasture did not differ between treatments but changed after 1 year of treatment (Table 4). At the start of the trial, the stand was mostly legumes, mainly alfalfa. After one year, legume levels dropped by almost 30% on average in all three liming treatments, while grass content increased by 16% for Pelletized and Ag Lime, and 47% for Wood Ash. The control was the only treatment in which grass content decreased (16%) from 2024 to 2025, and the legume percentage decreased by just 2%. Weeds increased across all treatments, rising by an average of 12% from the first to the second year.
Forage quality
The forage quality of the various treatments is shown in Table 3. There was no significant effect of treatment and year on CP content, with ranges of 16.1–19.1% observed between treatments and over the two years. A non-significant effect was observed for energy, whereas a significant effect was observed for year, as the energy content of all treatments increased from 2024 to 2025. There was a significant effect of treatment and year on phosphorus, with the Wood ash treatment showing the highest increase from 2024 to 2025. Calcium and magnesium levels did not differ significantly between treatments over the two years.
Key Messages From This Project
Liming works, but it takes time. After just one year, changes were small but moving in the right direction. Soil improvement is gradual, not instant.
Wood ash and pelletized lime showed the strongest early benefits. These two treatments led to big gains in forage yield (40–46%) compared to the control, which actually lost yield.
Soil conditions are starting to improve. Water infiltration and soil moisture improved in limed areas, while soil compaction dropped slightly — meaning soils are becoming easier for roots and water to move through.
Wood ash added useful nutrients. Calcium and sulphur levels increased the most where wood ash was applied, showing it can act as both a liming material and a nutrient source.
Don’t expect big pH changes right away. Soil pH did not shift much after one year, which is normal. Lime reactions often take 2–3 years to fully show up.
Pasture mix will shift as soils improve. As soil conditions change, grasses tend to respond first. Legumes may dip short-term, but are expected to recover as pH stabilizes.
Forage quality stayed solid. Protein and energy levels remained good across all treatments, meaning yield gains did not come at the cost of feed quality.
Early results are promising — but this is just the start. Continued monitoring in 2026 will help confirm whether pH stabilizes, legumes rebound, and long-term pasture productivity improves.
References
AAFRD (2004). Liming Acid Soils. Alberta Agriculture, Food, and Rural Development. Agdex 534-1. Alberta Agriculture and Food.
Flynn R., Ball S. T., Baker R.D. (1999). Sampling for Plant Tissue Analysis, Guide A-123. New Mexico State University.
PCBFA (2024). PCBFA Annual Report.
NSAC (Nova Scotia Agricultural College (2025). Liming Pastures. Fact Sheet, June, 2025. https://nsfa-fane.ca/wp-content/uploads/2025/06/Liming-Pastures.pdf
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