How to Lower Your Soil pH With Garden Sulfur
If you have alkaline soils with a high pH, plants face the challenge of a lack of accessible nutrients. Amending with garden sulfur is an easy way to work towards optimal pH levels. If you hope to grow healthier ornamentals and edibles or encourage those bluest of blue hydrangea blooms, explore sulfur as an amendment with garden expert Katherine Rowe.
Contents
We don’t often consider sulfur when we think of essential plant nutrients, but it’s vital in basic processes and soil health. Microbes help the mineral undergo a biological process in the ground, making it accessible to plant roots. Sulfates help plant development by balancing pH levels, leading to happier, healthier plants.
If your soil is alkaline, it has high pH levels (above 7.5). The sweet spot for most cultivated plants is between 6.0 and 7.0, slightly acidic to neutral.
While some plants, especially local natives and their cultivars, grow well in alkaline conditions, others suffer from chlorotic disorders. Alkalinity blocks access to nutrients, leading to yellowing leaves and a lack of vigor.
By balancing pH, sulfur helps lower alkalinity, leading to healthy plants. The proper pH makes all the difference in nutrient absorption. With testing and recommendations, making slow adjustments to your pH is achievable for thriving plants.
Lower PH: Garden Sulfur
- Effective pH Reduction
- Improves Soil Characteristics
- Targets Problematic Soils
- Nutrient-Rich Formula
- Promotes Plant Health
Why is Soil pH Important?
pH, or “potential hydrogen,” relates to acidity or alkalinity. Specifically, it’s a measure of hydrogen and aluminum ions. pH ranges from 0 to 14, with 7.0 being neutral. Planting areas with low hydrogen levels are alkaline, with a higher pH level.
Most cultivated plants grow best in mediums with a pH between 6.2 and 6.8. These slightly acidic to neutral pH levels provide optimal access to nutrients and other benefits.
Alkaline conditions (also known as sweet or basic) have pH levels between 7.5 and 9. Growing conditions with high pH levels are less soluble, making it more difficult for roots to uptake nutrients.
The best way to determine pH is with a test. At-home kits that interpret the results and offer recommendations help assess conditions and what needs improving. Your local university extension office is another resource for tests and recommendations.
Factors That Affect pH
The main factors that impact pH are climate, soil type, and organic matter. Western parts of the United States, where it’s drier with high temperatures, have more naturally occurring lime and are alkaline. In eastern areas that receive more rainfall, the dirt tends to be more acidic. Researchers created a map of worldwide pH levels that shows the role of climate and pH.
Texture also affects pH. Sand, clay, and silt particles impact how minerals like sulfur and lime infiltrate the ground. Accumulated organic matter, too, is a primary factor in pH. Leaves and pine needles break down in the dirt, which may lower the pH over extended periods of time. Compost is a way that this mineral enters the earth and increases pH.
Alkaline Soils
Alkaline soils contain sodium carbonate, raising the pH and limiting access to micronutrients like iron, manganese, zinc, and macronutrients like sulfur. Iron chlorosis is common when alkalinity is above 7.5.
Sulfur has the most significant impact on plant growth through organic matter. It enters the earth through the matter, and as microorganisms break it down, roots absorb the sulfates. This is a continual, naturally occurring process. Irrigation and rainwater also deposit this nutrient at the ground level. Minerals with sulfur, like gypsum and epsomite, break down over time and may be more alkaline.
Removing organic materials and topsoil decreases sulfur. Deficiencies affect crops much the same way nitrogen deficiencies do. They may show yellowing, chlorotic leaves. With low access to this micronutrient, yellowing occurs on new leaves.
Alkalinity means that the pH is higher than 7.5. If your planting areas are naturally alkaline, grow trees, shrubs, and perennials that are well-suited to those conditions. You can also amend areas with garden sulfur to lower the soil pH level and increase acidity. Move the pH toward slightly acidic (around 6.8) for the most widespread growing preferences.
Basics of Garden Sulfur
Garden sulfur is an organic amendment mostly used to lower the soil pH level and make the ground less alkaline.
Sulfur occurs naturally and is necessary for overall plant health. While its central role is lowering pH, it’s also essential in forming amino acids that build proteins. It’s part of photosynthesis. It benefits microbes in the nitrogen fixation and decomposition process. It plays a role in the oils of certain crops, like onions and garlic.
For plants to benefit, sulfur needs to become sulfate in the earth. Adding this nutrient causes a biological process that, aided by bacteria, produces sulfate and hydrogen, lowering pH levels.
Consider texture, organic matter, and plant selection before adjusting the pH level. A soil test helps determine the best amendment and quantities. Depending on the results of the soil test, you may need varying amounts of sulfur to lower the pH.
Benefits
Lowering alkalinity creates better conditions for most plants to thrive. As the pH level moves toward neutral or slightly acidic:
- Nutrients become more available for root absorption.
- Beneficial microorganisms are the most present and active.
- Soil structure improves. Neutral pH soils have a balanced texture that promotes good aeration and moisture retention for healthy root development.
Sulfur also contains calcium, adding to plant nutrition.
Application
This is an organic amendment. Bacteria produce sulfates, which lower pH. The process takes two to three months to realize pH adjustments. It may take longer in areas with very high alkalinity, cool growing conditions, standing water, or fewer bacteria present.
Apply elemental sulfur in the spring when microbes are most active. Warm conditions in the ground above 55°F (13°C) are best. The ground should be moist but not overly saturated or flooded. Wet planting areas lack oxygen, leading to a different breakdown process and that memorable rotten-egg smell (and plants won’t benefit).
The microbes aren’t active in winter, so a fall application limits viability. Spreading no more than 20 pounds per 1,000 square feet per year is recommended. If planting areas need more after testing in a few months, wait until the following season.
If you’re working around existing plants, rinse the leaves after application to remove any residue. Lingering powder can burn leaves.
Applying an overage of sulfur is too much of a good thing. It lowers the pH to acidic levels and may cause plants aluminum toxicity. While other nutrients become less available, aluminum availability increases.
To spread this amendment, distribute it across the ground and incorporate it into the dirt to provide microbes with ready access to the material.
Amending different soil types requires varying amounts of this amendment. The quantities for clay soils differ from those for loams and sands. Follow the pH testing and application guidelines for your site.
Frequently Asked Questions
What plants grow in alkaline conditions?
Buckeye, honey locust, viburnum, boxwood, geranium, yarrow, phlox, and dianthus tolerate slightly alkaline conditions.
How does sulfur affect hydrangea bloom color?
Sulfur helps lower pH. A lower pH (higher acidity) yields blue blooms. An alkaline pH (higher pH) produces pink shades. Neutral conditions create purple-blue to mauve petals. This is the case for bigleaf hydrangeas, where pH impacts flower color.
What happens if you add too much sulfur?
Sulfur is a naturally occurring mineral that benefits plants, but too much leads to root damage, stunted growth, and leaf drop.
