by Dr. Don Ball
The cost of fertilizer, especially nitrogen fertilizer, has sharply increased recently because fertilizer production and transport are linked to energy costs. This is a serious development for forage/livestock producers, because fertilizer usually accounts for 40 percent or more of the cost of producing forage, with nitrogen fertilizer alone often accounting for 20 to 40 percent of the cost of producing grass forages. Here are some ideas regarding possible ways to minimize fertilizer expenses.
Applying fertilizer without having taken a soil test amounts to guessing how much fertilizer is needed. Applying too much fertilizer is a waste of money; applying too little will result in less-than-optimum forage production. It is also important to follow liming recommendations on soil tests, because fertilizer nutrients are less available when the soil pH is low.
In many situations the single most beneficial technique for lowering nitrogen fertilizer costs is to grow forage legumes, usually with grasses. In association with Rhizobium bacteria, clovers and other legumes obtain nitrogen from the atmosphere and "fix" it in small nodules (knots) that form on the legume roots. The amount of nitrogen fixed varies due to several factors, but the ranges of nitrogen fixed in terms of pounds of N per acre per year by a good stand of (for example) an annual legume, by white clover, or by red clover is usually 50 to 150, 75 to 150, and 75 to 200, respectively. This means that if 100 pounds of N per acre are fixed and nitrogen is selling for $0.45 per pound, $45 worth of nitrogen per acre was added per acre.
In addition to providing biological nitrogen, a legume/grass mixture may produce more dry matter per acre than grass alone, particularly as compared to grass receiving little or no nitrogen fertilizer. The distribution of forage growth in pastures may also be more favorable, thus helping reduce stored feed needs. However, the single most valuable advantage forage legumes offer is better forage quality on average than grasses, which usually sharply increases animal gains and may enhance livestock reproductive rates.
Use Organic Materials–
Another strategy is to use organic materials such as manure or by-products from animal industries or various commercial processes as a source of fertilizer nutrients. In particular, broiler litter is commonly spread on pastures in Alabama, but other organic wastes are increasingly being used in this manner as well. At current prices, the nutrients in a ton of broiler litter are worth around $45 to $55.
The feasibility of using organic waste materials depends on two factors. First, is the value of the nutrients in the material high enough to justify the cost of obtaining and applying it? To answer this question requires knowing the level of nutrients in the material as well as how much will actually become available to plants. The second factor is whether the material contains any pathogens, heavy metals, or other undesirable components that could be harmful to animals, humans, or to the soil. If neither of these factors is a problem, then using a waste material as a soil amendment may be quite justifiable.
Urea As A Nitrogen Source–
Urea is usually less expensive than other sources of nitrogen, but it is also more volatile and more likely to be lost during warm weather. However, applying urea during warm weather may be justifiable in many situations if it is substantially cheaper than other nitrogen sources. The potential losses of urea by volatilization during warm weather can be significant, but in recent research by Auburn University scientists, losses in pasture situations were rarely greater than 10 to 20%. Losses are lower when there is little pasture growth present and/or if the soil pH is less than 7.0. Liquid nitrogen is usually a mixture of urea and ammonium nitrate, but only the urea component is vulnerable to volatilization loss.
Prioritize Fertilizer Application–
Not every acre of pasture is equal, because some areas have a much higher yield potential than others. For example, a rich, deep, and relatively level bottomland pasture may be much more productive than an eroded, thin hillside. The reasons are that on the hillside water runs off quickly, the soil may not hold nutrients well, and roots may only have a few inches of good soil in which to grow. In the bottom there will probably be better moisture and nutrient availability during most of the growing season and roots can penetrate deeply. The point is that the first priority should be on providing nutrients in areas that have the potential to be most productive.
Timing Of Fertilizer Applications–
If funds to invest in fertilizer are limited, it makes sense to time the applications so that extra pasture forage will be produced when it is most needed. For example, on a farm in north Alabama that is not heavily stocked, there may be excess forage available in spring. In such a situation, money spent for fertilizer applied in autumn would result in more valuable forage production by stimulating autumn grazing or for stockpiling fescue forage to help reduce hay requirements.
Utilization of pasture forage is greatly affected by grazing method. In fact, research has shown that in many poorly managed continuous grazing situations, less than half the forage produced in a pasture ends up being consumed by livestock. On the other hand, with good grazing management the percent of utilization of the forage produced may be 20 to 30% higher. This is the same result that would occur if 20 to 30% more fertilizer was applied.
There is no single answer to the problem of higher nitrogen fertilizer costs. To minimize these costs, different producers will need to take different approaches based upon their location, resources available, and type of operation. In fact, a given producer may need to take different approaches at different times or in different fields.
Don Ball is an Extension Forage Crop Agronomist with Auburn University.