Ultisols are highly weathered soils that are found mainly in humid regions with temperate or tropical climates. They can support productive forests but are acidic and have low quantities of plant-available calcium, magnesium, and potassium. This makes them poorly suited for continuous agriculture without the use of fertilizer and lime.
Properties
Ultisols are common in much of the southeastern United States but they’re also found as far north as a sliver of New York State’s Southern Tier. Their pH values typically range from 4.5 to 5.5. Because they contain iron oxides, Ultisols are often reddish or brownish in color. They also contain an appreciable amount of translocated silicate clay, which makes them prone to soil compaction and slow water movement.
Problems
Ultisols pose significant challenges for land management because they are nutrient deficient, acidic, and susceptible to erosion.
- Nutrient Deficiencies: The strong, long-term weathering processes that form Ultisols cause the leaching out, or loss, of calcium, magnesium, and potassium. This limits plant growth and can lead to the excessive use of fertilizers.
- Acidity: Ultisols’ acidity also limits plant growth because it reduces the available amount of phosphorous and other nutrients. Plus, acidic soil conditions can promote aluminum toxicity, a condition that inhibits root growth in some plants.
- Erosion: Ultisols have poor soil structure but are typically found in regions with high rainfall amounts. This makes them prone to surface erosion, especially in areas that are deforested or lack vegetation.
Solutions
Land management solutions for Ultisols involve addressing nutrient deficiencies, acidity, and the risk of erosion. The following practices can help.
- Lime: Lime, or calcium carbonate, can reduce soil acidity and alleviate aluminum toxicity. This is essential for crops, such as alfalfa and soybeans, that are sensitive to soil acidity.
- Fertilizer: Regular and balanced fertilization with nitrogen, phosphorus, and potassium, along with micronutrients like zinc and copper, can boost plant growth. Organic amendments such as compost or manure can also increase soil fertility.
- Low Till / No-Till Farming: Practices such as low-till or no-till farming and cover cropping can reduce erosion and improve water retention.
Ultisols present challenges for farmers and ranchers, but effective land management practices can mitigate the problems with these soils.