Improving Permeability and Salt Leaching in Irrigated Sports Fields: Exploratory Testing
S. Miyamoto, Ignacio Martinez, Francisco Luna, and David Tirre
Many sports fields developed in the El Paso Valley and some in uplands became salinized when irrigated with water containing 800 to 1,200 mg/L of dissolved salts. The soil types, which were salinized, include compacted soils, clayey Entisols, stony sediments along foothills, and some areas containing an indurated calcic horizon. Salinity of these soils was initially less than 3 dS m-1 in the saturation extract, and has increased over a decade or two in excess of 10 dS m-1, sufficient to deter growth of most turf grass species. The study reported here was preformed for evaluating various mechanical means of improving soil permeability for enhancing salt leaching. Observation included two municipal parks consisting of sandy alluvial soils, five sports fields consisting of clayey alluvial soils, sports fields consisting of topdressed stony alluvial soils or developed on an indurated calcic horizon through topsoiling. The equipment tested included a rotary tiller, a vibratory spike, aerifiers, a minimum-till surface chisel, a subsoiler, a backhoe, and a front-end loader. Field management practices were left to discretion of cooperators. Soil salinity and photo records of turf response were used as the primary means of the treatment impact.
The most significant reduction in soil salinity was found when stratified silty clay was either inverted to the new profile sequence of loamy sand over the fractured silty clay clods or mixed with the loamy sand layer below. Replacement of clays with sandy soils in a corrugated surface to permit lateral drainage was also highly effective in salt leaching in deep clay. Subsoiling of Glendale and Saneli silty clay loam followed by topdressing with a thin layer of sand also resulted in good salt leaching, especially when flood-irrigated using the Rio Grande water. The subsoiling shanks penetrated 20 to 30 inches deep, or almost to the full extent of the clay layer. It is uncertain if salt leaching can be improved when used in deeper clay, such as Tigua silty clay. The use of minimum-till shallow chisels provided an excellent fracturing of the surface clay layer (6 to 8 inches deep), but salt leaching was limited due to internal drainage impairment. The use of aerifiers did not improve salt leaching, at least at our test sites. Nonetheless, surface implements, especially minimumtill shallow chisels can be used advantageously for renovation or for sustaining high use fields consisting of loam. These preliminary test results are consistent with an earlier finding that soil salinization problems are closely tied with clayey soil textures. Test results also indicate that drainage impairment caused by the clay layer is probably as common as the difficulties with water intake for leaching salts.
Since soil improvement measures to be used depend upon soil type, the field should be surveyed for soil type and its distribution prior to planning soil improvement activities. Irrigation systems and scheduling should also be checked. The primary goal of soil improvement activities is to improve soil permeability, water movement and salt leaching, and must be complemented by prudent turf management practices to obtain turf response. There is a need to examine the existing codes or specifications for construction of new fields for improved salt leaching. The current construction codes for sports fields emphasize soil strength and stability, but not salt leaching.