RESEARCH REPORT
Fertilizer Influences on Soil and Turf Quality
Dr. Wayne R. Kussow
Department of Soil Science
University of Wisconsin-Madison 1525 Observatory Drive
Madison, WI 53706-1299
SUMMARY
All of the fertilizers tested maintained satisfactory color throughout the abbreviated 1996 growing season. The Country Club 18-4-10 generally provided the lowest color ratings. The Spring Valley 12-1-12 consistently out-performed the Spring Valley 21-3-12. This is likely due to the fact that the 26-3-12 has substantially more of its N in the form of SAWS N (Nutralene).
As expected, season average bentgrass color and clipping N concentrations were significantly related to each other (r = 0.673*). Clipping P and K concentrations were uniformly high and were not significantly related to the amounts of fertilizer P and K applied. This is to be expected, given that the soil on the experimental site tests high in both nutrients. Were soil test levels of P and K not high, chances are that responses to the Natural sciences 12-0-0 and Lorganic-8 (8-0-0) would have been less than observed.
Bentgrass root weights measured in October showed very little response to the fertilizer treatments. There was a tendency for more root growth in treatments with low clipping weights, but the relationship was not significant.
The fertilizers appeared to induce substantial changes in soil microbiological activity. The responses ranged from a 56% reduction in activity to a 153% increase over the period of May to August. There were marked changes in biological activity between August 18 and September 11 as well. Often these changes were inconsistent for a given treatment; i.e., a substantial increase in microbial activity during the May to August period was followed by a large decrease during the August to September period.
The large shifts in microbial activity were not significantly related to ben tgrass color ratings, clipping weights, clipping analyses, root weights or dollar spot incidence. These results are subject to numerous interpretations. One could be that not enough time has elapsed to see the effects of changes in microbial activity manifested in the bentgrass. Other possibilities are that soil microbial activity is not a major importance in intensively managed turf or that the methodologies used are unable to detect significant influences. The latter is a distinct possibility and one that will receive attention in 1997.