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s'" u ?"" Applied Research'continued Table •• and Relative Soil MobilityPlant Mineral Nutrients. loam soil with a 5% slope was intentionally compacted using a Ionic Form(s) vibratory roller before an addi- tional 3 inches of silt loam topsoil Nutrient Symbol AbsorbeYBy Plants . .ility in Soil was placed on top of the com- pacted area and either tilled or Nitrogen N NH4',NO3 NH4'Immobile; left in a layer before seeding NO3 Mobile Kentucky bluegrass.By year two Phosphorus P HPO HPO 2 Mainly Immobile of the study,runoff amounts from P 2 4 4 Y both compacted and non-com- Potassium K K+ Somewhat Mobile pacted plots were similar (e.g.,1.2 to 1.5 inches of runoff annually Calcium Ca Ca t+ Mainly Immobile from 25.2 total inches of annual precipitation). Magnesium Mg Mgt+ Immobile • Core aerification of established Sulfur S SO42• Very Mobile turfgrasses growing in compacted r soils can improve the speed at Micronutrient which water moves into soil i (Partsch et al. 1993;Stier 2000). BoronB B033- Mobile The growth of turfgrass roots, freezing and thawing of soil and Chlorine Cl Cl- Mobile the activity of soil macro-organisms, Copper Cu Cu + Immobile including earthworms,can also PP improve infiltration (Easton et Iron Fe Fee+, Fe3+ Immobile al.2005). Manganese Mn Mn2+ Mobile •The loss of sediment from healthy lawns is often very low(Soldat and Molybdenum Mo Mo042- Somewhat Mobile Petrovic 2008) and is unrelated to the level of P in soil unless it is Zinc Zn Zn2+ Immobile unusually high (Soldat et al.2009). The small but consistent level of Soil texture,structure,pH,clay type and organic-matter content influence nutrient retention and/ soluble P in runoff waters from or plant availability in soil (Roberts 2000). For example,sandy soils usually hold fewer nutrients turf probably originates from plant and have higher water-infiltration rates than soils high in clay(e.g.,clay,clay loam,sandy clay tissue (Soldat et al.2009). and silty clay).The availability(solubility)of boron,copper,iron,manganese,phosphorus and zinc for uptake by plants is reduced in soils having a very high pH.Ctther nutrients(including calcium, •When reactive P loss from unfro- magnesium,potassium and sulfur)are readily available for plant uptake from soils with a high pH. zen turf fertilized for three years Montmorillonite clay is capable of holding more nutrient cations(positively charged ionic form) with a high P:N (1:2)fertilizer was than illite or kaolinite.The nutrient-holding capacity of a soil most often increases as the organic- compared to reactive P loss from matter content increases. unfrozen turf receiving a low P:N (1:27)fertilizer,a K:N fertilizer and etation) or turf swale can intercept and Waddington 1999). The no fertilizer annually,a significantly flowing water before it reaches researchers noted that the condi- greater reactive P loss (0.1 lb.P per an impervious surface (Asleson tion,structure and history of a soil acre) from turf receiving the high et al.2007;Schneider 2007). are largely a function of construe- P:N fertilizer occurred in the first tion practices before planting. year only(Bierman et al.2010).In •Soil compaction may contribute the second and third years of the to runoff.A study of 15 lawns in • Recent research in an upper Mid- study,reactive P losses from non- central Pennsylvania revealed that west lawn demonstrated that,in fertilized turf were greater than a'soil's condition,structure and some cases and over time, the those from any of the fertilized history may be more likely to af- effect of pre-plant soil compaction turfs.The researchers attributed feet water infiltration rates in lawns on the rate of water infiltration this increase to limited density and than the texture (percent sand, may be less of a problem than higher runoff volumes compared silt and clay) of the soil (Hamilton perceived (Kussow 2008).A silt to fertilized turfs. 32 ",VIRGINIA TURFGRASS JOURNAL September/October 2012 www.vaturf.org �3 - � �