Effect of Alum Treatments on Turfgrass Coverage and Runoff Losses during Establishment

Incorporation or top-dressing of composted biosolids (CB) can enhance turfgrass establishment and sod properties at harvest, but soil phosphorus (P) and nitrogen must be managed to protect water quality. Alum treatment of CB could reduce soluble P concentrations in amended soil and limit runoff loss of P. The objective was to evaluate CB and Alum effects on turfgrass coverage of soil and runoff losses during 'Tifway' bermudagrass (Cynodon dactylon (L.) Pers. var. dactylon · C. transvaalensis Burtt-Davey) establishment from sprigs or transplanted sod. Three replications of eight treatments comprised a complete randomized design. Four treatments were composed of 'Tifway' sprigged in soil with and without incorporation of CB and Alum. Four remaining treatments were sods harvested from 'Tifway' grown with and without top-dressed CB that were transplanted with and without a surface spray of Alum. Surface coverage of 'Tifway' sprigged in soil mixed with inorganic fertilizer or CB was comparable to transplanted sod 25 days after planting. In contrast, Alum incorporation acidulated soil, slowed coverage rates of sprigged 'Tifway', and increased NH4-N runoff loss during early establishment in treatments without CB. Incorporation of Alum with CB or inorganic fertilizer in soil before sprigging reduced soil water-extractable P (WEP) more than 38% and reduced runoff loss of soluble reactive P (SRP) in three of four establishment treat- ments. Although SRP runoff loss from CB-amended sod was greatest among treatments, the Alum spray minimized SRP loss after transplanting. Alum effectively reduced runoff loss of SRP from CB, soil, and turfgrass sources during establishment from sprigs or sod. Additional field research is needed, but incorporated or surface sprays of Alum offer a potential new practice for mitigating runoff loss of SRP from establishing turfgrass. Topdressing or incorporation of large, volume-based rates of composted biosolids (CB) can increase storage of soil organic carbon (SOC), supply essential mineral nu- trients, and enhance turfgrass coverage dur- ing sod establishment and regrowth (Wright et al., 2005). Greater concentrations of soil total nitrogen (N) and phosphorus (P) and of soil-test P and potassium (K) were associated with greater SOC storage after transplanting CB-amended compared with fertilizer-grown 'Tifway' sod (Dai et al., 2009). The authors hypothesized greater soil-test concentrations of P and K in CB-amended sod could have increased turfgrass growth and contributions to the dissolved fraction of SOC. Previous reports of turfgrass responses to CB applied before sprigging, seeding, or regrowth supported the hypothesis that both sod growth and quality could be improved. Incorporation of 25% by volume of CB before sprigging increased 'Tifway' bermu- dagrass coverage 64% after 2 weeks and 23% after 8 weeks compared with soil without CB (Schnell et al., 2009). Similarly, incorpora- tion of a 1.3-cm layer of CB within a 10- to 15-cm depth of excavated soil enhanced visual assessments of percent cover and clipping yields of seeded cool-season turf- grasses (Loschinkohl and Boehm, 2001). Top-dressing of dried biosolids at rates up to 100 Mgha -1 during regrowth of a tropical grass, kikuyu (Pennisetum clandestinum Hochst. Ex Chiov.), achieved higher than acceptable color ratings (Tesfamariam et al., 2009). In addition, top-dressing of the biosolids at rates up to 33 Mgha -1 enhanced