What is Nutrient Management?

Matthew F. Stephens  |  10/4/2004 4:25:25 AM

To understand nutrient management, you must first understand what nutrients are. Nutrients are substances that are essential for plant growth such as nitrogen, phosphorus and potassium (potash). These three nutrients are the main ingredients in any mixed commercial fertilizer.

Consider triple thirteen (13-13-13) and understand what each number symbolizes. In commercial fertilizer, the first number is the percentage of nitrogen (N) that the mix contains; therefore this mix will contain 13% nitrogen or 13 pounds of nitrogen per 100 pounds of fertilizer. The second number represents the percentage of phosphorus (P) the mix contains, and the third number is the percentage of potassium (K)the mix contains. So, if someone applies 200 pounds of triple thirteen, the field receives 26 pounds of each nutrient.

Plants use different amounts of each nutrient to produce fruit, fiber, forage, etc. Producers must know the needs of the plants before they can determine what and how much fertilizer is needed. Since plants can use only so much of each nutrient, all excess nutrients accumulate in the soil, leach through the soil or run off the field with water. What happens to the excess nutrients depends on many factors such as soil type, slope, water table, ground cover, etc.

Each particular nutrient affects plant growth in different ways. The following is a short description of each nutrient’s function in forage production.

Nitrogen (N)

Nitrogen is the element that is usually most limiting in hay production. It is a constituent of protein. Proper rates of nitrogen increase growth rate and photosynthesis. Nitrogen deficiencies are characterized by a light green color and poor growth. Hybrid Bermuda grass hay requires high rates of nitrogen to maximize yields. Nitrogen losses are caused by volatilization, leaching and runoff.

Phosphorus (P)
Phosphorus is critical in the establishment of a root system. It is essential in the storage and transfer of energy and is a component of several biochemical actions that control plant growth and development. Phosphorus deficiency in warm-season grasses is exhibited as small, unthrifty plants. Phosphorus is used in much smaller amounts by hay than are nitrogen and potash.

Potassium (K)
Potassium (potash) is indirectly related to many cell functions. Some 60 enzymes require the presence of potassium. Plants sufficient in potassium are much more winter hardy than those plants that are deficient. Plants that are deficient in potassium are more prone to drought stress, certain diseases and winter kill. Bermuda grass hay removes tremendous amounts of potassium from the soil.

As previously stated, plants remove different amounts of each nutrient per unit of measure (tons, bushels, bales, etc.). The following is the amount of nutrients removed per ton of hay. Therefore, once a producer knows how many tons of hay is removed from a pasture, he or she can calculate how many pounds of nutrients are removed.

  • Nitrogen - Hybrid Bermuda ... 46 lb/ton of hay; Bahia...43 lb/ton of hay
  • Phosphorus - Hyrbrid Bermuda...12 lb/ton of hay; Bahia...12 lb/ton of hay
  • Potassium - Hybrid Bermuda...50 lb/ton of hay; Bahia...35 lb/ton of hay

Once a producer understands the amounts of nutrients that plants use, he or she should then determine the amounts of nutrients that need to be added to the fields. The only way to determine the amount needed to add to the field is to know the amount of nutrients that exist in the soil. This is done through a soil test, which can be obtained through the local LSU AgCenter’s Cooperative Extension Office. A soil test will indicate the nutrients present in the soil to determine what added nutrients are required. Each field should be considered on a case-by-case basis.

Poultry litter has an average of 60 pounds of nitrogen, 60 pounds of phosphorus and 40 pounds of potassium per ton. This equates to a commercial fertilizer mix of 3 - 3 - 2 or 3% nitrogen, 3% phosphorus and 2% potassium. These amounts are averages and will vary with different farms or production units. It is recommended that a litter analysis be conducted for each farm.

Once a producer knows what is needed to produce the hay and the amount of nutrients that are present in the field, he or she can decide how much is needed to produce the amount of desired forage.

Although there are many more factors in nutrient management, this is a short explanation of the major points of managing a producer’s fertilization costs. With production costs rising at a steady pace, producers should consider ways to maximize yields while minimizing costs.

For more information on maximizing yields while minimizing costs through fertilizing, contact your local county agent.

What is Nutrient Management?
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