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Commodities: Field Crops: Forages

Summary of soil test results from pastures and hayfields originating from the Southern Coastal Plain soil province in Georgia between 1996 and 2007.*

Dennis W. Hancock and Richard Hitchcock
Asst. Professor and Forage Extension Specialist, Crop & Soil Sciences Dept., and
Senior Systems Support Specialist, Agricultural and Environmental Services Laboratories, University of Georgia

Soil pH

Soil pH is a measure of soil acidity. When soils are too acid (pH is too low) crop growth will be reduced. Most forage crops grow best when the soil pH is 6.0 – 6.5. However, some legume species require a slightly higher soil pH (e.g., alfalfa requires a pH of 6.5 – 7.0).

pH
Figure 1. The percentage of soil samples from pasture and hay land in the Southern Coastal Plain that fall within specific soil pH ranges.

Phosphorus

Phosphorus (P) is an essential plant element that plays a key role in many vital plant processes such as root development, reproduction, and energy transfer. In the Southern Coastal Plain, soil test P levels are divided into four ranges for most forage crops: low (0 – 30 lbs/A), medium (31 – 60 lbs/A), high (61 – 100 lbs/A), and very high (100+ lbs/A).

P
Figure 2. The percentage of soil samples from pasture and hay land in the Southern Coastal Plain that fall within specified ranges in soil test phosphorus.

Potassium

Potassium (K) is second only to nitrogen in the concentration found in plants and is essential for producing economical yields (especially when stress conditions occur). In the Southern Coastal Plain, soil test K levels are divided into four ranges for most forage crops: low (0 – 60 lbs/A), medium (61 – 150 lbs/A), high (151 – 250 lbs/A), and very high (250+ lbs/A).

K
Figure 3. The percentage of soil samples from pasture and hay land in the Southern Coastal Plain that fall within specific ranges in soil test potassium.

Calcium

Calcium (Ca) is critical for several basic functions in the plant (cell growth, stress detection, signaling, cell division, etc.). Fortunately, Ca deficiencies are rare in Georgia, especially if the soil has been limed. In the Southern Coastal Plain, soil test Ca levels are divided into two ranges for most forage crops: low (0 – 200 lbs/A) and adequate (201+ lbs/A).

Ca
Figure 4. The percentage of soil samples from pasture and hay land in the Southern Coastal Plain that fall within specific ranges in soil test calcium.

Magnesium

Magnesium (Mg) is a critical element of chlorophyll, the green pigment in plants that enables photosynthesis. It is fairly common for Mg to be deficient in Georgia. In the Southern Coastal Plain, soil test Mg levels are divided into three ranges for most forage crops: low (0 – 30 lbs/A), medium (31 – 60 lbs/A), and high (61+ lbs/A).

Mg
Figure 5. The percentage of soil samples from pasture and hay land in the Southern Coastal Plain that fall within specific ranges in soil test magnesium.

* From soil samples received and analyzed at the University of Georgia’s Agricultural and Environmental Services Laboratories’ Soil, Plant, and Water Lab.