Zoysia is a lawn grass variety noted for its ability to resist infestations from pests and disease. It can also survive in poor soil. Though not entirely carefree, the need for less fertilization is also a benefit of zoysia. The amount of fertilizer and time to fertilize depend on both the maturity of the lawn, the climate in which it is in and the owner's expectations of the lawn's appearance.
Zoysia grass does best when fertilized with a complete fertilizer containing nitrogen, phosphorous and potassium in a ratio of 1:2:1. At least one-fourth of the available nitrogen in the fertilizer should be derived from a slow-release source. This is indicated in the ingredients and can be either sulfur-coated urea, ureaformaldyhyde, or water-insoluble nitrogen. Lime or sulfur may need to be applied to adjust the pH of the soil. Zoysia does best in soil with a pH of 6.0 to 6.5.
At the time of establishment, 1 to 2 pounds of nitrogen should be applied per 1,000 square feet of lawn area. For established zoysia lawns, 1 pound of nitrogen should be applied per 1,000 square feet of lawn area. The formulation on a bag of fertilizer represents the percentage of that element in the bag. For example, a 50 pound bag of 5-10-5 fertilizer does not contain 5 pounds of nitrogen, but rather 5 percent, or 2.5 pounds.
Zoysia lawns should be fertilized when first established in the spring. After that, apply two more applications can be applied three to four weeks apart in moderate climates. In warm climates, you can fertilize an additional time in fall if it is in a location where the grass remains green all year. If a fall application is given in moderate to cool climates, the lawn may produce new growth, which will be too tender to withstand the cooler temperatures of winter.
To keep a zoysia lawn looking healthy, employ a few other cultural practices in addition to fertilization. Mow zoysia lawns frequently at a height of about 1 to 2 inches every five to seven days. Less frequently can result in scalping of the grass when mowed. A vertical cut, such as by a reel mower, should be used. Dethatch zoysia lawns in the fall.