Foraging Ahead with Dr. Don Ball: Getting the most out of forage nutrients
In recent years, increases in the cost of fertilizer nutrients have caused cattlemen and other livestock producers to create and discover economical ways to provide nutrients for production of forage. Since it appears that fertilizer costs are not likely to decrease significantly in the foreseeable future, these methods are more important than ever when it comes to maximizing forage nutrients.
Here is a table that is found in the fifth edition of the book Southern Forages. The table originally only provided the approximate total pounds of major nutrients removed by selected forage crops based on an assumed yield per acre. We’ve updated it to make it easier to compare nutrient removal by various crops. Pounds of nutrients removed per ton of forage have been calculated for the various forage crops and are now shown in parentheses.
The data in this table make several interesting points:
- Of the primary nutrients (nitrogen, phosphorus, and potassium), forage crops remove much more nitrogen and potassium than phosphorus.
- Nutrient removal per ton is virtually identical for the cool season perennial grasses tall fescue and orchardgrass.
- When you compare various forage crops on a nutrients-per-ton-of-forage basis, there are differences (mainly with regard to nitrogen), but perhaps not as much as one might think there would be. Forage yield is the most important determinant of nutrient removal; the higher the yield, the more nutrients removed.
- Alfalfa contains more nitrogen per ton of forage than bermudagrass (but of course alfalfa is a legume and fixes its own nitrogen).
- While establishment costs typically increase the expense of growing annuals as compared to perennials, this data shows that nutrient removal per ton by one widely grown summer annual (sorghum-sudan) is lower than nutrient removal per ton by bermudagrass.
Good forage production requires that adequate quantities of nutrients are available in the soil. Having some knowledge of the relative amounts of various nutrients required by various forage crops is helpful.
Recycle those forage nutrients
Nutrient recycling is an important issue that every livestock producer should think about on a regular basis. Grazing management and related management actions (such as location of minerals, placement of water sources, where to feed hay, etc.) that favor more even distribution of recycled nutrients in the form of manure and urine are desirable. Good pasture management can result in most of the phosphorus and potassium and perhaps half or more of the nitrogen in forage consumed by animals later becoming available for pasture forage growth.
The nutrients in hay or other stored feed brought onto a farm also will be recycled. Thus, the value of purchased feed is not limited to the nutrition it provides to animals. It also can subsequently provide nutrients to forage plants.
Nutrient removal from hay fields is much greater than from pastures. When forage is cut for hay, most of the above-ground nutrients are removed; in pastures, a high percentage of the nutrients in forage can be recycled and eventually result in additional forage production with less need for application of fertilizer.
Seventeen nutrients are essential for plant growth. Nitrogen, phosphorous, and potassium are the major nutrients and needed in the greatest quantities, followed by secondary nutrients calcium, magnesium, and sulfur. The major nutrients frequently need to be provided, and the secondary nutrients may need to be as well, depending on the forage. The other essential nutrients are minor elements needed in small amounts and in many forage production situations are naturally available in sufficient quantities.
Having adequate quantities of the various essential forage nutrients available helps ensure that forage yield, forage quality, and competitiveness of forage crops will be acceptable. Soil testing to determine nutrient availability, having a basic understanding of the amounts of various nutrients present in forage, and employing management practices that favor good nutrient recycling facilitate having an economical forage/livestock program.
Foraging Ahead is a bi-weekly column presented by Ragan & Massey and written by Dr. Don Ball, Professor Emeritus at Auburn University. Dr. Ball is one of the authors of the popular book “Southern Forages,” available here.