Important Considerations for Pasture Fertilization

— Written By and last updated by JoAnne Gryder

With spring upon us, many producers have already started planning on pasture and nitrogen cyclehayfield fertilization. Unlike fertilization of most field crops, where the decision as to the amount and type of fertilizer to apply is largely driven by trying to achieve optimum production, pasture fertilization should be more controlled by careful consideration of the individual goals for the pasture. Factors to consider include: 1) production needed for the animals; 2) time of forage needs; 3) species present; and 4) expected methods of management.

With nitrogen and fertilizer costs expected to be higher than last year, this has convinced many producers to take a closer look at the need to lime and fertilize this spring. While cutting back on certain fertilizer and liming practices will help your immediate economic cash flow, it could reduce your overall profits for the year. Pastures require nutrients to be productive. These nutrients are derived from several sources including residual nutrients in the soil, nitrogen produced by Nitrogen-fixing organisms in legumes, nitrogen from rain and snow, nutrients derived from the breakdown of manures and organic matters in the soil and lastly nutrients applied from fertilizers and lime.

In some situations, a fair percentage of nutrients can be derived from these residual fertilizer sources, however; seldom can the entire nutrient needs be met without some commercial fertilizer application. The only way to know what residual nutrients are available is to soil test. Never has it made more sense to soil test than now!!! Another factor that needs consideration is the availability of these nutrients to the plant. While most soils have some level of nutrients present, if the soils are acidic (low pH), the negatively charges particles bind some of these nutrients to the soil so that they are not available for the plant to utilize. In these soils, the most economic beneficial application would be that of lime rather than higher levels of fertilizer. Pastures that have significant percentages of broom sedge often need lime or phosphorus. The only sure way to know is to soil test! Following are a few tips to help make the best economic use of your lime and fertilizer budget:

1. Soil test. Even though it will likely take about 6 weeks to 2 months to get your results, you can use a standard recommendation of 50-60 lbs. of actual nitrogen (150 -175 lbs. of 34-0-0) per acre and make up any deficiencies in a later application in summer or fall. The only true way to know what you need is to know what is available in your soil and what nutrients the forage you are growing needs.

2. Lime. If you have not limed in the last 2-3 years, chances are you will need an application of lime (1-2 tons per acre), especially if you are noticing an increase in broom sedge. Pastures that receive higher levels of nitrogen to increase yields will tend to become acidic more rapidly requiring more frequent applications of lime.

3. Utilize livestock and poultry manures whenever it is economically and environmentally feasible. These sources are often available at a lower cost than commercial fertilizers. There are also by-product and municipal waste sources available that make excellent liming and/or fertilizer sources. However, often there is paperwork required in the utilization of these low cost resources and there may also be a limitation as to how much can be used.

4. Apply only the nutrients you need! Fertilizers are sold based on the percent nitrogen (N), phosphorus (P) and potash (K) in the blend. 100 lbs. of 17-17-17 contains 17 percent nitrogen, 17 percent phosphorus and 17 percent potash. 100 lbs. of 18-46-0 contains 18 % nitrogen, 46% phosphorus and 0% potash. Many of our soils have adequate levels of potash. On these soils, utilizing 17-17-17 to meet fertility needs would give unneeded levels of potash. Soil test and match the ratio of N-P-K in the fertilizer blend used to the ratio of N-P-K recommended for soil.

5. Split Nitrogen into 2 or more applications. Soil test reports will give a standard recommended rate of 120-200 lbs. of N per year. Nitrogen is very volatile and can move or leach from the soil rapidly compared to P and K. Usually a majority of the nitrogen applied in a commercial fertilizer is gone in 60 days. Applying the entire N in one application would put more N than a crop could use at one time and leave pastures deficient towards the middle and end of the season giving us a reduced annual yield.

6. Interseed clovers into your grass stand to help provide N for your grasses. Clovers are legumes and have the ability to fix nitrogen in the soil making it available for grasses to utilize. This is an excellent way to economically increase production of grass pastures. (Legumes do require a higher pH than grasses; so, be sure to provide adequate lime)

NCSU Cooperative Extension