Abiotic Factors That Affect the Growth of Grass in a Lawn

Environmental Factors

• Soil that is too dry or too wet can result in damage to grass in lawns. Insufficient water causes the grass to turn brown and can be fatal if the roots dry out too much. Grass can scald or scorch in boggy areas during periods of high temperatures. In addition, grass in boggy areas is more prone to root diseases caused by fungi or bacteria. Most types of grass do not grow well in shady areas and have fewer roots and shoots than when grown in sunny areas. The blades of grass are thin and tall and spread less, which results in bare spots. Soils that contain a high percentage of clay are prone to compaction, as are areas of lawn where people frequently walk or drive. Compacted soil contains fewer and smaller air pores, so water and grass roots cannot freely move through the soil. This results in areas with little or no grass where weeds can grow.

Nutrient Deficiencies

• Grass that is not receiving enough of the proper nutrients will not thrive. Insufficient nitrogen is the most common nutrient deficiency. Grass that does not get enough nitrogen turns yellow and grows slowly. A lack of sufficient potassium causes the margins of grass blades to turn yellow or brown. Dark patches of purple grass indicate a lack of phosphorus. An iron deficiency typically occurs in alkaline soils and causes the grass to appear mottled with yellow or bleached spots.

Chemical Damage

• Applying fertilizer too heavily or to a wet lawn can burn the grass, causing brown, gray or white stripes in the lawn. Severe damage can result in the death of the grass. The damage follows the pattern in which the fertilizer was applied and occurs soon after fertilization. Overspray from weed killers is usually apparent within a few days. Leaf blades may be spotted or complete blades may be scorched and die, depending on the type of product used.

Mowing Injuries

• Mowing the lawn with dull blades, during a drought or when the grass is wet, shreds the leaf tips. The damaged grass turns gray soon after mowing; then turns yellow or brown and dies. This weakens the lawn and makes it more susceptible to diseases or drought. Scalping, or mowing the grass too short, exposes the stem tissue. The damaged grass turns yellow or brown. Scalping also occurs in areas where the mower deck does not remain level, such as on slopes or uneven surfaces, as well as in weedy turf or heavy thatch.

Other Factors

• Grass turns yellow or brown under gardening tools, water hoses, lawn furniture, toys or other items left on the lawn. If the item remains in the same place for a long time, the grass may die. Dog urine causes circular dead patches of grass surrounded by a dark green circle in lawns. Female dogs cause more damage to lawns than male dogs. Creeping types of grasses recover from the damage faster than bunch types of grasses.