By Blake Jackson
Livestock manure is a valuable fertilizer resource, particularly for supplying phosphorus (P), one of the most expensive nutrients required for crop production.
In many beef operations, manure often contains more phosphorus than crops actually need. While this surplus creates nutrient management challenges, much of the excess can be traced back to feeding practices that can be adjusted.
Phosphorus is the second most abundant mineral in an animal’s body and plays a critical role in metabolism, growth, and reproduction. Because of its importance, rations are frequently formulated above National Research Council (NRC) recommendations.
Nutritionists often include a “safety margin” to account for variations in animal requirements, feed phosphorus levels, delivery accuracy, and bunk management. Concerns about phosphorus availability and reproductive performance also contribute to higher inclusion rates.
However, phosphorus levels vary widely among feed ingredients. Cereal grains and byproducts such as wheat middlings and soybean meal are typically higher in phosphorus than forages, which can be inconsistent in nutrient content.
Relying solely on book values may result in overfeeding. Testing feed ingredients and balancing rations based on laboratory analysis can help ensure cattle receive adequate-but not excessive phosphorus.
Another issue arises with mineral supplements. Many bagged mineral mixes are designed for all classes of cattle. Since feeder cattle on grain-based diets already consume sufficient phosphorus, adding a general mineral supplement can significantly oversupply this nutrient.
Excess dietary phosphorus is excreted in manure, contributing to soil phosphorus buildup when manure is applied based on nitrogen needs rather than crop phosphorus requirements.
Elevated soil phosphorus levels can take 10 to 20 years of crop production to decline once applications stop. Evaluating soil tests field by field and applying manure only to maintain optimal phosphorus levels is a key best management practice.
By fine-tuning rations to meet, but not exceed, phosphorus requirements, producers can lower feed costs and reduce environmental impact.
FAQs
- Why is phosphorus important in cattle diets?
It supports metabolism, bone growth, and overall animal performance.
- Why do cattle often receive too much phosphorus?
Safety margins and generic mineral mixes can lead to over-supplementation.
- How does excess phosphorus affect the environment?
It accumulates in soil and can contribute to water quality problems.
- How can producers reduce manure phosphorus levels?
By formulating rations to meet, not exceed, phosphorus requirements.
- Why should feed ingredients be tested?
Testing ensures accurate nutrient balancing and prevents overfeeding.
Photo Credit: gettyimages-imaginegolf
Categories: Pennsylvania, Livestock, Beef Cattle