Farm Basics #1161 Soil pH and Nutrient Availability (Air Date 7-5-2020)

Summary

In this discussion, the impact of soil pH on nutrient availability is explored. The presenters highlight how both high and low pH levels can affect essential nutrients like phosphorus and manganese, making them less available to plants. Practical advice is provided for adjusting soil pH, such as using lime to raise pH and sulfur to lower it. Aiming for a neutral pH range (6-7) is recommended for most crops, lawns, and gardens. The video also touches on how soil amendments can address pH imbalances and improve plant health, while noting that pH doesn't influence weed control.

Takeaways

• 😀 Soil pH has a significant impact on nutrient availability for crops, affecting how well plants can absorb nutrients.
• 😀 Manganese availability tends to be lower in high pH soils (7 or above) and higher in lower pH soils (5-6).
• 😀 Phosphorus availability is influenced by soil pH, with high pH soils binding phosphorus with calcium, making it insoluble and unavailable to plants.
• 😀 In low pH soils (4-5), phosphorus binds with iron or aluminum, making it less accessible to plants as well.
• 😀 The ideal soil pH range for most crops is around 6-7, as it allows for better nutrient availability and absorption.
• 😀 To raise the pH of acidic soils, lime (calcium carbonate) can be applied, improving nutrient availability and fixing soil issues like dog urine spots in lawns.
• 😀 For high pH soils, elemental sulfur can be used to lower the pH by forming sulfuric acid.
• 😀 Proper soil pH balance is crucial for ensuring that crops, lawns, and gardens receive the nutrients they need for healthy growth.
• 😀 Soil pH can be affected by salts and sodium, especially in fields, which may require improved drainage to help lower the pH.
• 😀 Different crops have varying pH preferences, with some thriving in slightly acidic or alkaline soils, which is important for farmers to consider.

Q & A

What role does soil pH play in nutrient availability for crops?

Soil pH significantly affects the availability of nutrients for plants. A pH that is too high or too low can cause certain nutrients to bind with other elements, making them unavailable for plant uptake. Maintaining a balanced pH is crucial for optimal nutrient absorption.

How does soil pH affect manganese availability?

Manganese availability is higher in soils with a lower pH (around 5-6), whereas soils with a pH of 7 or higher show lower manganese levels. This indicates that lower pH levels are better for manganese availability to plants.

What happens to phosphorus availability in high pH soils?

In high pH soils, excess calcium binds with phosphorus to form calcium phosphate, which is insoluble in water. This makes phosphorus unavailable to plants, despite it being present in the soil.

What is the effect of low soil pH on phosphorus availability?

In low pH soils, phosphorus binds with iron at higher pH levels or with aluminum at very low pH (below 5). This binding prevents phosphorus from being available to plants.

How can soil pH be adjusted to improve phosphorus availability?

Soil pH can be adjusted to improve phosphorus availability by raising the pH to around 6 to 7, where phosphorus is more accessible to plants. This can be achieved by using calcium carbonate to raise the pH or sulfur to lower it.

What is the function of calcium carbonate in soil pH management?

Calcium carbonate, or lime, is used to raise soil pH in acidic soils. It neutralizes acidity, making essential nutrients like phosphorus more available to plants.

How does calcium carbonate help with dog urine spots on lawns?

Dog urine is acidic, which can lower the pH in specific spots on a lawn, causing damage. Applying lime (calcium carbonate) raises the pH, helping to restore the balance and repair the damage.

What effect do salts and sodium have on soil pH?

Salts and sodium in the soil tend to raise the pH, leading to alkaline conditions. This can hinder nutrient availability and affect plant health, which is why it's important to manage drainage and remove excess salts.

How can elemental sulfur help in lowering soil pH?

Elemental sulfur can be applied to soils with high pH to lower it. It reacts with the soil to form sulfuric acid, which helps reduce the pH, making nutrients more available to plants.

What pH range is ideal for most crops, lawns, and gardens?

A soil pH between 6 and 7 is ideal for most crops, lawns, and gardens. However, certain plants may require slightly lower or higher pH levels, and adjustments can be made based on the specific needs of the crops.