Soil for Lawn or Turf
The soil is an important factor in the successful establishment of turf grasses. It acts as a reserve for nutrients and water. Air pores assure sufficient oxygen content and promote the breakdown and decomposition processes by micro-organisms. The soil material has to be resilient in recovering from the pressures of wear and tear encountered in extreme turf use circumstances.
Soil Characteristics and Grass Development
Strong and healthy grass growth with sufficient wear resistance is only possible if a number of soil criteria are met. To assess a turf soil, look at :
Particle Size: a good mixture of fine, medium and coarse fractions allows resistance to wear, good base foundation and good drainage.
Pores: a well-balanced relation of fine, medium and large pores guarantees regular gas exchange in the soil.
Water Permeability: depends on the percentage of large pores .
Water Capacity: is defined by the amount of fine and medium pores in the soil.
Bulk Density: indicates the degree of compaction and potential root density.
PH: is a measure of the acidity / alkalinity of the soil. The availability of nutrients and the activity of nutrients vary according to the pH. Low pH severely limit the availability and uptake of nutrients by plants.
Cation Exchange Capacity: determined by the mineral and organic colloids . CEC is a measure of soil’s ability to hold cations. The larger the value of the CEC , the higher the soil’s ability to retain nutrients.
Suitability of Soil for Turf
Fertilizer practices vary according to soil type and end use. For landscape turf one normally simply utilizes the existing soil types. Special soil preparation practices may occur for regularly utilized turf, especially sports turf. Generally speaking, it is necessary to modify the soil characteristics by varying the granular composition, and by mixing in soil conditioners, in order to optimize grass growth, and to attain a high level of resistance to wear.
Optimum Nutrient Levels in Soil
Specialized constructions based on sand for sports turf and golf greens are characterized by a low capacity to deliver nutrients. The adequate feeding of plants requires all main nutrients such as N, P, K, S, Mg, Ca, etc to be present in soils at sufficient levels.
The High nutrient demand of grasses is satisfied with regular fertilizer application during vegetative period. Depending on turf type and grass varieties, the necessary nutrient quantities vary from 10-40 Gm N/m. sq /year
pH Control :
The pH indicates the acidity / alkalinity of the soil sample. It influences grass development, soil structure, bacterial activity, thatch built-up and the availability of nutrients in the soil. For turf grasses a range of pH 5.5 – 7.3 is acceptable. Turf grasses for sports fields and golf greens prefer pH levels of 5.8 – 6.5. With regular soil testing one can assess the levels of the main nutrients required in order to adopt a fertilizer regime. Optimum levels are given in the table; the higher values represent turf surfaces with high usage.