| Abstract/Contents: | "This study was initiated at the Iowa State University Horticulture Research Station in Ames, Iowa, during the spring of 1989. The objective of this study was to observe the effects of six fertilizer sources and core cultivation on turfgrass quality, clipping production, root density, and physical soil properties. The six fertilizer sources include: Urea 46-0-0 (Synthetic fast-release organic); IBDU 31-0-0 (Synthetic slow-release organic); Ringer Turf Restore 10-2-6 (Natural organic); Ringer Green Restore 6-1-3 (Natural organic); Milorganite 6-2-0 (Natural organic); Ureaform (Blue Chip) 38-0-0 (Synthetic slow-release organic). Urea was applied at 1 lb N/1000 ft2 on May 15, June 15, August 15, and September 15, 1990. All other fertilizers were applied on May 15 and August 15 at 2 lb N/1000 ft2. Core cultivation treatments consisted of two passes with a Ryan Lawn-Aire 28 just before fertilization on May 15 and August 15. This resulted in approximately 20 holes/ft2/treatment. Traffic stress was initiated on May 15 and consisted of five passes each Friday with a water-filled smooth roller. Traffic stress resulted in a combination of wear and soil compaction. Due to the extremely wet summer of 1990, the predominant traffic stress was soil compaction. One undisturbed soil sample was collected from each plot on October 15. Total porosity, air-filled porosity, bulk density, and soil strength were determined for each sample. Fertilizer source had little effect on soil physical properties (Table 34). While there was as difference in bulk density at the 10% level of probability, the differences were minor. The effects of cultivation treatments were much more pronounced. Core cultivation and traffic stress had a significant effect on soil physical properties. Plots that were core cultivated had a soil strength of 2.9 and an air-filled porosity of 20.2%, while plots that were not cultivated had a soil strength of 3.2 and an air-filled porosity of 18.9%. This shows the ablility of core cultivation to alleviate soil compaction. Soils receiving weekly traffic had greater soil strength (3.4 vs 2.8), increased bulk density (1.42 vs 1.31), and lower total pore space (38.6 vs 40.0) than soils that received no traffic. There were no interactions between variables. Visual quality ratings and clipping yield samples were collected on a weekly basis. Shoot density, thatch, and root density samples were collected on June 30. Visual ratings were based on a visual scale of 9 to 1. A rating of 9 equals a dark green, dense turfgrass, whereas a rating of 1 equals a straw-brown turfgrass stand. A rating of 6 was used as the minimum acceptable level of quality. Clippings were collected by removing all leaf tissue over 2 in within a 21 in by 5 ft area (8.75 ft2) down the center of each plot. Clippings were placed in paper bags and dried. Weights were recorded as grams/8.75 ft2. Shoot density was determined by counting the number of tillers/15 in2 at three locations for each plot. Thatch depths were measured by taking two 3-in diameter plugs from each plot. The thatch was compressed with a 2 kg weight and depth was measured as mm. No difference was found for either shoot density or thatch development. Hence, the data is not shown. Root density samples were collected by taking six cores from each plot with a 1-in diameter soil probe. Samples were divided into 5 cm segments. Soil was washed from the roots, which were dried and ashed. Data is reported as mg of organic matter/25 cm3. Fertilizer Source: The effect of fertilizer source on visual quality is presented in Table 35. Urea had an overall quality of 7.8, followed by Restore 10-2-6 (7.2), Restore 6-1-3 (7.0), Milorganite (6.7), Blue Chip (6.5), and IBDU (6.4). Plots treated with urea, IBDU, and Restore 6-1-3 exhibited a quicker spring green-up. Following the first fertilizer application for 1990, all treatments provided acceptable quality. While there were treatment differences on each measurement date, no one fertilizer maintained consistently better quality over the others. The effect of fertilizer source on clipping yields is presented in Table 36. Urea produced the greatest amount of clippings (181.1 g), followed by Restore 10-2-6 (172 g), Restore 6-1-3 (162 g), Milorganite (129 g), IBDU (98 g), and Blue Chip (93 g). Treatments with higher yields corresponded to the better quality ratings. Urea-treated plots demonstrated quicker growth in the spring. By early June, both Restore-treated plots produced the greatest amoung of clippings. After mid-June, the urea-treated plots produced the most clippings. There were no major effects of fertilizer on root density (Table 37). However, minor differences did occur at the 10% level in the 10 to 15 cm soil zone. Milorganite had the greatest root mass followed by Restore 10-2-6 and Blue Chip. Core cultivation: The effects of core cultivation were evident on several measurement dates (Table 35). Core cultivation improved quality on June 13, June 20, July 25, August 1, and August 14. Core cultivation adversely affected quality on September 19. The high temperatures in September couploed with a more open turf due to core cultivation may well have been responsible for the lower quality in September. Core cultivation had very little effect on clipping yields (Table 36) and root density (Table 37). Traffic Stress: Overall, traffic decreased visual quality of Kentucky bluegrass (Table 35). Traffic reduced visual quality on March 29, April 20, June 20, June 26, August 1, August 8, August 14, September 11, and September 19. Interestingly, visual quality was greater for traffic plots on May 13, 2 days prior to the onset of traffic treatments. Traffic had a minor effect on clipping yields (Table 36) and increased surface rooting (Table 37). An increase in surface rooting is common on sites that are heavily compacted. However, it is rare that these differences show up in field situations." |
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