SportsTurf provides current, practical and technical content on issues relevant to sports turf managers, including facilities managers. Most readers are athletic field managers from the professional level through parks and recreation, universities.
Issue link: https://read.dmtmag.com/i/43432
FieldScience to 0.50 inch) reduces wear damage due to greater cushioning and provides better trac- tion or footing compared to no thatch. Ex- cessive thatch or mat without sufficient sand integrated into it greatly increases potential for tearing and divoting action and will have poor rooting stability. During dry periods on high-sand fields, excessive organic matter can also foster water repellant, hydrophobic areas where the grass is susceptible to greater wear damage and reduced root stability. Excessive tissue succulence increases sus- ceptibility to wear injury since tissues are more fragile due to less total cell solids (im- portant factor in wear tolerance) but higher water content (by weight). Conditions fos- tering succulent grass are too high nitrogen, low light conditions, excessive irrigation, and poor surface or subsurface drainage where the grass is growing in excessive moisture. Shoot tissue cells exhibiting low turgidity adjustment) and cannot be substituted for by another cation or organic osmolyte. Potas- sium deficiency also causes stomata to re- main open in grasses with high water loss and reduction of cell turgidity. Typically, higher potassium rates are recommended for recreational sites compared to general turf- grass areas. On all but high sand-content, root-zone media, soil testing is the best method of determining potassium needs with a target range within the upper medium range for extractable potassium. On irrigated sand fields, potassium can be easily leached making it difficult to maintain soil test values. Losses also occur if clippings are removed. However, too much potassium can increase soluble soil salt levels during prolonged dry periods without any leaching losses, and reduce water uptake. For high- sand, irrigated, recreational turfgrass sites, many research scientists (including the au- During the winter several types of wear injuries can occur: wear on dormant tissues; traffic on frosted green leaf tissues (disrupting brittle protoplasm); and traffic on thawed surfaces where the underlying soil remains frozen. are much more susceptible to wear injury than plants under normal cell turgidity. Low cell turgidity results from lack of sufficient cell moisture to maintain a turgid cell wall that resists wear stresses where conditions contributing to low cell turgidity are: a) in- adequate soil moisture; b) lack of a good root system to take up soil moisture during hot, low humidity periods; c) soil salinity from saline irrigation water inducing physio- logical drought stress on the plant; and d) inadequate potassium for osmotic adjust- ment of the plant to drought stress. Manage- ment practices to address situations that foster low cell turgidity are especially impor- tant during field use periods; and this in- cludes avoiding mowing on a drought stressed field since this can cause consider- able shoot tissue injury including death. Adequate plant potassium deserves some attention since it contributes to total cell solids and maintenance of cell water for turgidity (rigid cells). For example, research on seashore paspalum under saline irrigation water has demonstrated that potassium is re- quired for > 25% of cell turgidity (osmotic 14 SportsTurf | October 2011 thor) suggest that potassium fertilization rates be coupled with nitrogen application rates and timing with the following sugges- tions for recreational grasses when the irriga- tion water is not saline: a) < 6 lb N per 1000 ft2 per year, use a 1:1 N: K20 ratio; b) > 6 lb N, use a 1:0.75 N:K20 ratio. During rainy periods when soil K may leach, foliar appli- cation aids in maintaining adequate shoot tissue K and cell turgidity. If the irrigation water is saline, especially when sodium is moderate or higher, a higher N:K20 ratio such as 1:1.5 may be necessary along with periodic foliar K application. Applications of K based on N rates are only for heavily leached sand media. Unfortunately, many turf managers with K-retaining fine-textured soils have used the "ratio method" (ignoring soil tests) resulting in excessive K applica- tions and promoting build-up of K (a salt) within the soil especially in prolonged dry periods. The nature of the grass species and culti- vars within a species influence the wear toler- ance of the grass. Characteristics that enhance wear tolerance are: a) high inherent shoot density coupled with an adequate shoot growth rate; b) strong and deep root- ing grasses that resist tearing actions; c) grasses with good lateral stolon/rhizome growth; and d) a grass that is adapted to the climatic and pest stresses and mowing regime at the site so that it can maintain good growth. Wear tolerance differs from soil compaction tolerance so results from studies should be evaluated for what mix of traffic stresses were actually present in the study. Over the past 10 years several research scien- tists have evaluated relative wear tolerance and mechanisms (physiological, morphologi- cal, and anatomical plant differences) that contribute to superior wear tolerance of a cultivar within a species, which can vary con- siderably from the general ranking for a species. Turfgrass species and cultivars of a species vary not only in wear tolerance but also wear recovery. Plant aspects influencing rapid recuperative potential include: high inherent growth rates; presence of lateral stolons and/or rhizomes; and physiological health of the plant, especially carbohydrate reserve levels. During the winter several types of wear injuries can occur: wear on dormant tissues; traffic on frosted green leaf tissues (disrupt- ing brittle protoplasm); and traffic on thawed surfaces where the underlying soil re- mains frozen. Traffic on dormant tissues causes considerable wear since there are no live green leaves to cushion the pressure and no regrowth. Dormant warm-season grasses overseeded with a cool-season species can tol- erate more traffic as the overseeded grass pro- vides a protective cover and cushioning. However, the primary grass may decline over time from overseeding competition. SOIL FACTORS Soil texture has a strong influence on dif- ferent types of wear as well as proneness to soil compaction. Sandy, well-drained soils, while resistant to soil compaction and less prone to water-logging than fine-textured soils, are more susceptible to being droughty that requires careful irrigation to avoid drought stress during field use. High-sand content fields at field capacity have better traction and stability to resist tearing action and divoting than when drier. If the irriga- tion water is saline, sandy soils compared to www.sportsturfonline.com