Interactive Effects of N and K on Drought Avoidance of Turfgrass
Maintained as Fairway
Dr. Scott Ebdon, University of Massachusetts, 2 years, $5,000/year.
Objective(s): 1. To investigate the interactive effects of N and K on perennial ryegrass
growth and physiology maintained at fairway height. 2. To determine the optimum N:K
nutrient combination levels that maximize turfgrass quality during periods of limited water
availability.
Results: Approved. Project to begin Summer of 2001.
2001 Results: The results reported here are preliminary since they were based on only one year of data from a multiyear study. A problem associated with the continuous use of high rates of N and K derived from fertilizer salts is excess soil salinity. Therefore, we plan to collect data over the next several years in order to evaluate the long-term effects of high K fertilizations on turfgrass performance. Additionally, we are planning to evaluate N-K effects on drought resistance.
In summary, potential benefits were observed with added K when applied at rates that exceed generally accepted K recommendations based on soil tests. These benefits are summarized in Table 6. The benefits from added K were dependent on the level of N and therefore were the result of K interaction with N. Interactive effects and associated K benefits were observed with N at levels that are routinely applied to turfgrass. A major benefit from added K through its interaction with N is the potential to reduce N without sacrificing functional (acceptable) turf grass quality. Depending on the seasonal period, the maximum gain in turf quality observed with added K would be the equivalent to increasing N from 3 to as high as 7lbs/1,000ft2/yr.
Table 6. Potential benefits associated with potassium (K) interaction with nitrogen (N).
- Although soil tests indicated high K levels, benefits were observed with added K in these N-K studies.
- Benefits associated with added K were detected with N at levels typically applied to turfgrass (i.e., 1, 3, and 5lbs N 1,000ft2/yr):
Benefits/Comments
Recuperative potential:
5 lbs N (w/ 9 lbs K) provided recovery rates equivalent to 9
lbs N/1,000ft2/yr.
Implication(s):
Added K may enhance recovery from wear.
K enhanced turf quality (TQ):
Late spring/early summer TQ: 3 lbs N(w/ 9lbs K) = 7lbs N.
Late summer stress recovery: 1 lb N (w/ 9 lbs K) was superior to all other N-K treatments.
Late fall/early winter TQ: 3 lbs N (w/ 9 lbs K) = 5 lbs N.
Implication(s):
K can substitute for N, reducing the potential for surge growth during pre-stress periods.
By reducing N, added K may enhance rooting, reduce water use, and increase drought survivability.
Winter cover :
At low N levels (1lb/l,000ft2/yr), added K enhanced green cover.
Implications(s):
Enhanced turfgrass quality, photosynthetic capacity, and carbohydrate reserves.
K enhanced rooting:
At low N levels (1lb/l,000ft2/yr), rooting density increased
with added K within the upper 4-inch soil profile.
Implication(s):
Greater surface rooting may increase traction (footing), but accelerate wilting.
Disease:
Unless excessive N levels were applied (7 and 9 lbs), K did not alter severity of brown patch or snow mold diseases.
Implication(s):
Any of the benefits observed with added K did not sacrifice disease resistance at N levels routinely applied to turfgrass.
- Some negative implications and precautions with added K:
Precautions/Comments
K enhanced surge growth
7 lbs N (w/9 lbs K) increased shoot growth by 60% over low K combinations (1lb K/1,000ft2/yr).
Implication(s)
Reduced rooting, increased brown patch severity, and accelerated decline in summer turf quality.
