Improve Swine Manure Nutrient Use

By Scout Nelson

Sushant Mehan, Assistant Professor and SDSU Extension Water Resource Engineer Specialist, along with Anthony Bly, Bob Thaler, Sara Bauder, and Peter Sexton, highlight improved phosphorus management in swine systems. Managing phosphorus in swine manure is becoming more important for modern farming. While phosphorus is essential for plant growth, too much of it can harm soil health and water quality. Many farmers apply manure based on nitrogen needs, but swine manure often contains more phosphorus than crops require. This leads to phosphorus buildup in soil over time.

Phosphorus supports root growth, energy transfer, and seed development in crops. However, only a small amount of phosphorus in soil is available to plants. Much of it binds with other elements, making proper management important for both crop yield and environmental protection.

Swine manure is a valuable nutrient source, but its composition depends on animal diets and growth stages. Pigs do not absorb all the phosphorus they consume, so a large portion is excreted. This makes feeding strategies an important tool for managing manure nutrients.

One key factor is the nitrogen-to-phosphorus ratio. Most swine manure has a low ratio, which causes phosphorus to be overapplied when manure is spread based on nitrogen needs. Improving this ratio helps reduce long-term soil buildup.

Feeding strategies such as phase feeding can better match nutrients to animal needs, reducing waste. Alternative feed ingredients may also affect phosphorus levels, but results can vary. One of the most effective solutions is using low-phytate corn.

Low-phytate corn allows pigs to absorb more phosphorus from feed, reducing the amount excreted in manure. Studies show this can lower manure phosphorus levels by about 40 percent. It also improves nutrient balance and reduces the risk of phosphorus runoff into water sources.

Farmers should also test soil and manure regularly and adjust application rates based on both nitrogen and phosphorus needs. Soil type and field conditions should be considered when applying manure.

Overall, better feeding decisions can turn manure into a more balanced nutrient resource. Small changes can improve soil health, protect water quality, and support long-term farm success.

Photo Credit: gettyimages-magicxeon