Alum Effects on Phosphorus Runoff Loss from Turfgrass Amended with Biosolids

1. Alum Effects on Phosphorus Runoff Loss from Turfgrass Amended with Biosolids R.W. Schnell, D.M. Vietor, C.L. Munster, T.L. Provin, and R.H. White, Texas A&M AgriLife Results and Discussion Table 4. Mean biomass and total nutrient concentration in Tifway clipped at soil surface of box lysimeters 40 d after planting. Introduction • Composted biosolids (CB) are a bio-resource for organic C and nutrients • Incorporation of volume-based CB rates can conserve soil and water and • enhance turfgrass establishment in urban soils • Volume-based CB rates can be top-dressed during turfgrass sod production • and recycled during transplanting of CB-grown sod back to urban landscapes • Large CB rates reduce sod wet and dry weight and soil removal at harvest • CB sources of P and K in sod reduce fertilizer needs after transplanting • Despite benefits, CB imported with sod are potential nonpoint nutrient sources • Both dissolved P and organic C are potential contaminants of surface waters • Compounds containing Al could be mixed with CB to reduce solubility and • nonpoint-sources losses in runoff during turfgrass establishment Table 2. Mass loss of sediment and total N and P in runoff 20 d (Rain 1) and 37 d (Rain 2) after sprigging (Sp) or Transplanting sod (Sd) of Tifway bermudagrass. Tifway was established with and without CB and Alum (Al) amendments. • Greater biomass and total P content • within clippings of CB-amended sod • indicated thatch layer could have • contributed to runoff loss of SRP • Greater biomass could have limited • sediment and total P and N loss from • sodded compared to sprigged • treatments at 20 d after planting. • Variation of SRP concentration was • attributed to variation of WEP within the • 0- to 5-cm depth of sprigged treatments • at 20 d (r2 = 0.79) and 37 d (r2 = 0.66) • after planting (Fig. 5). • Variation of soil WEP accounted for < • 50% of variation of runoff concentration • for transplanted sod • Incorporated or surface spray of Alum • did not affect runoff loss of soluble • unreactive P (SUP) except for SdCB • (Table 3). Objectives • Evaluate runoff losses during establishment of Tifway bermudagrass sprigs • or transplanted sod with and without CB and Alum. • Relate soil phosphorus and organic C concentrations to runoff concentrations • Runoff volume was similar among treatments (1.2 cm depth for 8 min.) • Sediment loss was greatest for Tifway sprigged in soil without CB (Table 2). • Variation of sediment loss indicated soil was primary source of TN and TP • loss at 20 d • At 37 d, variation among treatments indicated soil and top-dressed CB were • runoff sources of total P • The lack of Alum effects on TP loss in runoff from sprigged Tifway indicated • P bound to Alum hydrolysis products was detected in unfiltered digests. Materials and Methods • Three replications of eight treatments installed in box lysimeters (Table 1) • Flumes were mounted on downslope side of lysimeters (Fig. 1 and 2). • Applied Alum (1 g Al kg-1 Alum) at 0.1 g g-1 CB and/or turfgrass clippings • Alum was incorporated with soil or CB, or sprayed on the surface of sod Figure 5. Regression of WEP vs SRP. Table 1. Tifway was sprigged or transplanted as sod in sandy loam soil packed within box lysimeters under greenhouse conditions. Inorganic fertilizer or CB was incorporated in soil before sprigging and sod was transplanted from Tifway grown with or without CB. • Soil organic C (SOC) was greater with • than without CB amendments (Table 3). • Comparable runoff of dissolved organic • C (DOC) between treatments with and • without CB indicated both CB and • Tifway thatch were DOC sources (Fig. 6) • Surface sprays of Alum reduced DOC • runoff loss from transplanted sod, but • Alum incorporated with CB did not (Fig. 6) Table 3. Analyses of pH, organic C (SOC), and water-extractable P (WEP) in soil sampled to 5-cm depth at 40 d and of total dissolved P (TDP) and soluble unreactive P (SUP) in filtrate of runoff from lysimeters 20 (Rain 1) and 37 d (Rain 2) after planting. Figure 6. Runoff loss of dissolved organic C. • Contrasting establishment treatments • similarly affected variation of runoff • concentration and loss of SRP and • DOC (Fig. 4, 6 & 7) • Regression analyses indicated SRP • and DOC variation were directly related • at 20 d (r2 = 0.71) and 37 d (r2 = 0.72) • after planting (Fig. 7). • Similar effects of Alum surface sprays • on SRP and DOC loss from transplanted • sods indicate Alum could be used to • manage both contaminants (Fig. 4 & 6). • Mean runoff loss of TDP at 20 d was greater for CB-amended sod without • Alum than seven other treatments • Although Alum reduced soil WEP for soil and transplanted sod mixed with CB, • TDP loss in runoff was similar with and without Alum for all but sod with CB • Alum-induced reductions of runoff TDP loss at 37 d indicated SRP bound to • hydrolysis products of Alum was retained in sod or sediment. Figure 1. Tifway sprigged in soil. Figure 2. Tifway sod transplanted on soil. Figure 7. Regression of runoff SRP vs DOC. • Runoff loss of SRP was greatest for • CB-amended sod without Alum • Alum more effectively reduced SRP • than TDP loss from sprigged or sodded • treatments with or without CB • A surface spray of Alum reduced SRP • loss more effectively for transplanted • sod than for CB incorporated in soil • Surface spray of Alum reduced WEP • within the surface layer after sod was • transplanted from top-dressed turf. • Simulated rain applied 20 and 37 d after planting (Fig. 3) • Oscillating, spray nozzel rain simulator applied 10 cm hr-1 • Composited runoff over three 8-min. periods on each date • Runoff filtered (<0.45 μm) and analyzed within 24 hr • Soil and clippings sampled after second rain event • Soil total, Mehlich-3, and water extractable P analyzed • Analyzed total dissolved and soluble reactive P in filtrate • Measured total N and P in digests of runoff • Analyzed total N and P in digests of clippings Conclusions • Incorporating large, volume-based CB rate limited runoff loss of sediment and • total N and P compared to soil without CB for sprigged Tifway. • Incorporation of Alum with CB or soil effectively reduced soil WEP concentration • and runoff loss of SRP during early establishment of sprigged Tifway. • A surface spray of Alum on transplanted sod effectively reduced runoff loss of • SRP and DOC from CB, soil, and turfgrass sources. • Variation of soil WEP and runoff concentration of SRP were directly related • during early establishment of Tifway bermudagrass sprigged in soil with or • without CB. Figure 3. Rain simulator Figure 4. Runoff loss of soluble reactive P (SRP) The authors are grateful for technical support of B.J. Allen and financial support from Turfgrass Producers International; the Texas Turfgrass Research, Education, and Extension Endowment; and Texas AgriLife Research and Extension