Soils: June 2002

Have you ever stopped to consider the cost associated with haying bermudagrass? Include fertilizer inputs, swathing, raking, baling and labor, and it can quickly add up to $30 a ton or more. With this kind of investment, it is important to implement proper management to assure a positive return.

Fertilizer management
When haying, forage is harvested from one field and either sold or fed in another area. Either way, essential plant nutrients are being removed from the hayed field. There are 50 to 60 pounds of nitrogen, 14 to 17 pounds of phosphorus and 30 to 40 pounds of potassium in one ton of bermudagrass hay. I will let you do the math, but large amounts of nutrients are removed when producing three-plus tons of bermudagrass hay per acre per year. It is important to replenish these removed nutrients to maintain an adequate level of production over time.

I recommend frequent soil tests to monitor soil nutrient levels and to make sure enough fertilizer is applied to meet the desired yield goal. Bermudagrass requires a lot of nutrients to yield a ton of forage. If fertility is not replaced, eventually the soil will be depleted of essential plant nutrients, which results in declining yields and increased weed problems. A proper balance of nitrogen, phosphorus, potassium and other nutrients is essential for improving nitrogen use efficiency. Fertilizing directly from soil test results is the best way to maintain a balanced system.

A good analogy is your truck. Let's say that nitrogen is gasoline, phosphorus is the battery and potassium is oil. Every time you pull into the station to fill your tank with gas, you don't change the battery and the oil. The battery and oil are important in the operation of the truck, but the gasoline is what makes it run. Nitrogen makes the plant grow. The ratio of N, P and K removed from the field in a ton of bermudagrass is approximately 4 to 1 to 3 — more nitrogen is needed to produce a ton of forage than phosphorus or potassium. However, if phosphorus and/or potassium are limiting, then nitrogen inputs won't be fully utilized.

Forage quality
We already know that total dry-matter yield increases with increasing nitrogen rates. The same is also true with forage quality. Crude protein increases with increasing nitrogen rates. Since the nutritive value of bermudagrass forage (crude protein) is directly related to nitrogen fertilization, it is important to harvest bermudagrass forage during the right stage of maturity to further capitalize on a fertilizer investment. Several factors can affect forage nutritive value, including temperature, rainfall, maturity and balanced fertility. Of course, we can't control the weather, but we do have control of fertility and harvest management. As bermudagrass matures, crude protein is diluted and some may be bound within the plant, making it unavailable to the animal. Table 1 shows the effect of nitrogen rate and stage of maturity on the nutritive value of bermudagrass forage.

Stubble height
Another important item often ignored when haying is stubble height. Typically, forage is cut extremely close to the soil surface when haying. This removes leaf area, which is important in the photosynthetic process. The more leaf area removed, the slower the recovery period.

Let's imagine that you are a kid mowing yards for the summer. One customer in town always wants her yard cut as short as possible. Why? Because she does not care about its appearance as much as she does about having to pay for it to be mowed. By mowing it short, it will be mowed less often through the summer, which is cheaper. Another customer is very particular about his yard. He wants it to be the prettiest in town and in perfect condition all summer, regardless of the cost. You will mow his yard weekly at a higher setting. Why? Because a higher setting will leave more leaf area, or "factory," for plant re-growth, and it also looks prettier. Through the summer you will make more money from the second yard due to the fact you are mowing it higher, which leaves more leaf and causes it to re-grow quicker, and as a result it has to be mowed more often.

In your pasture, you may slightly reduce your total yield per cutting, but you may get an extra cutting per year by cutting higher. Leaving a good stubble height also provides shade and cools the soil surface, creating an environment less favorable for weed germination. If you practice good soil fertility and forage harvest management, you should be able to sustain a quality level of hay production while reducing the need for herbicide inputs over time.