Golf Course Management

OCT 2013

Golf Course Management magazine is dedicated to advancing the golf course superintendent profession and helping GCSAA members achieve career success.

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research ments was as much as 13% greater than spring growth in plots treated with only nitrogen. This difference is likely a manifestation of post-regulation growth enhancement (6), also called the rebound effect. It is important superintendents recognize the sensitive nature of late-fall Primo Maxx application timing when considering such putting green treatments. Spring clipping yield Spring clipping yield (pounds/1,000 square feet) 2.0 Spring tissue nitrogen Nitrogen levels in spring putting green leaf tissue were unaffected by application date, which came as a surprise considering the effect on leaf nitrogen levels in fall (Figure 1). Spring leaf-tissue-nitrogen level was signifcantly enhanced by fall Primo Maxx treatment, regardless of timing or application regimen (split or full) (Figure 4). Thus, the late-fall Primo Maxx treatment resulted in greater nitrogen status compared to plots treated with nitrogen alone, yet also reduced early spring growth (Figure 3). This observation is in agreement with reports of nitrogen preservation within turfgrasses recently treated by Primo Maxx (4,7). 1.5 1.0 0.5 Primo MAXX + 0.61 pound nitrogen/1,000 square feet 0 Full Split 0.0 1 6 11 16 Summary 21 26 31 October (fall) application date Figure 3. Spring clipping yield by Primo Maxx treatment and fall application date (pooled experiments). Vertical bars show the least signifcant difference between mean values. Although early spring vigor is sometimes perceived as benefcial, and welcomed by the maintenance staff, it may increase turfgrass susceptibility to crown hydration injury (1). Continued regulation of growth, particularly when putting greens break dormancy with suffcient canopy density and nitrogen status, may reduce the likelihood of deacclimation injury caused by rapid onsets of freezing temperatures in early spring. Early spring clipping yield data were pooled over both seasons to best illustrate the interaction of treatment and timing (Figure 3). Application timing had little effect on spring growth response to the fall nitrogen-alone treatment. However, applications of Primo Maxx made later in fall (after the frst hard frost) reduced putting green spring growth by as much as 20%. In contrast, early spring growth of plots receiving early-October Primo Maxx treatments (before the frst frost) exceeded that observed in plots treated at the same time with nitrogen alone (Figure 3). Spring growth in plots receiving early Primo Maxx treat86 GCM October 2013 Applying nitrogen and Primo Maxx in late autumn can enhance the spring density and tissue nitrogen concentration of greens-height turfgrass systems. Application of Primo Maxx in late fall suppresses growth in early spring, even when tissue nitrogen is high. In fact, Primo Maxx signifcantly preserves tissue nitrogen, which can be benefcial for spring growth after Primo Maxx is no longer active and weather patterns stabilize. Conversely, Primo Maxx can be used to stimulate growth in early spring when applied up to two weeks before the frst hard frost, but this is not recommended because early growth may diminish hardiness. Spring density was signifcantly improved by the combination of Primo Maxx and fall nitrogen in the frst year of the study. Results show tissue nitrogen levels >4.0% mass at the onset of dormancy did not have detrimental effects in early spring. When striving for such a high concentration late in the season (September or later), nitrogen should be applied with a plant growth regulator such as Primo Maxx. This will restrict top growth and improve density going into winter. In theory, a plant that is photosynthetically active but not growing will synthesize carbohydrates, contributing to energy reserves and winter hardiness. Where winter injury threatens the health of a turfgrass system, maintaining a dense turfgrass canopy may ultimately reduce turf loss and aid in accelerated spring recovery.

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