A good fertilizer program is necessary for a healthy and vigorous lawn. It also must be accompanied by correct mowing heights, proper irrigation schedule and weed and pest control for the best results.
A well-planned fertilizer program includes applying the correct type and amount of fertilizer to the lawn.
The first step in establishing a quality lawn is determining the pH and fertility of the soil. A soil test is the best way to do this. For this discussion, Bermudagrass will be used as an example.
The acid/base scale ranges from 0 to 14. The midpoint (7) separates acid from alkaline soils. Any number below 7 indicates an acidic soil and any number above 7 indicates an alkaline soil. The pH of the soil is an important factor because nutrients become more available when the proper pH is achieved.
Bermudagrass, for example, grows best in soils with a pH between 5.5 and 6.5. If this pH is achieved, the fertilizer will be used by the turf. If this pH is not in this range, the fertilizer will be bound to other elements in the soil and not released to the turfgrass.
Regarding fertilizer, it is recommended that three applications at a rate from 2 to 5 pounds of nitrogen are made each year – in April, June and September – for Bermudagrass. With any fertilizer product it is important to follow the manufacturer’s directions. My recommendation would be a fertilizer with a composition of 16-4-8 in April, 16-4-8 in June and 5-10-15 in September. Fertilizer is labeled by its composition of nitrogen-phosphorus-potassium, expressed as percentages. The 16-4-8 is 16 percent nitrogen, 4 percent phosphorus and 8 percent potassium.
When pre-emergent herbicides are used for the lawn, more applications are added to the fertilization program. However, there are combination products that save time and money. Spring pre-emergents give three to four months of weed control and can be applied six to eight weeks apart.
For example, if a fertilizer with pre-emergent is applied as recommended in April, most product labels recommend a split application six to eight weeks apart at the high rate.
Therefore, the desirable timetable for the split application would be in early February and another in late April.
The application in February will ensure that early germinating weeds are eradicated when temperatures rise in March. Because of cooler temperatures, the fertilizer used should be 5-10-15 with pre-emergent, low in growth-promoting nitrogen. The second application in late April will prevent weeds from germinating until July. The fertilizer should be a 16-4-8 with pre-emergent, high in nitrogen to promote growth. This will condition the turf to thrive in hot weather. These two applications will promote a weed-free period from February to July.
The recommendation for the June application is a 16-4-8 fertilizer. This application will help replenish nutrients removed by environmental factors such as rainfall/irrigation, soil type and grass clippings that are removed during mowing.
Fall pre-emergents give several months of weed control and can be applied six to eight weeks apart. These applications use the same fertilizers as in the spring.
The recommended timetable for fall fertilizer is September, but under this schedule the first fall pre-emergent application should be in early August with a 16-4-8 fertilizer.
The second application would be in late October using 5-10-15 fertilizer with pre-emergent to ensure eradication of weeds until next February and ensure proper winter conditioning of the turfgrass. Then the fertilizer cycle repeats.