Optimization of turfgrass fertigation rate and frequency

Abstract

The main aim of turfgrass fertilization is to maintain high turf quality and obtain proper turf colour. Fertigation has been recognized as the best fertilization method for proper turfgrass nutrition and for minimizing nitrogen leaching. The aim of this study was to determine the optimum fertilizer rate and frequency for obtaining high-quality turfgrass and minimizing nutrient losses using a fertigation system.Lysimeter experiment was conducted on perennial ryegrass and Kentucky bluegrass mixture in 2016-2018. Three different fertigation rate treatments were applied: 60, 120, and 240 kg N ha−1 (NPK). Fertigation was applied at three intervals: 2, 4 and 8 days between fertigation (DBF). A control treatment with granular fertilizers (CTR) was also applied. The following turfgrass parameters were scored: leaf texture, overall appearance, turf cover and turfgrass colour. Additionally, colour was measured using a spectrophotometer. The colour parameters were expressed using the CIELAB colour system. Leached water samples were taken every two weeks during the vegetation period. The contents of the available forms of selected macro- and microelements (N, P, K, Mg, Ca, Na, Zn, Cu, Mn and Fe) were determined.The fertigation parameters, nutrient rate and interval between fertigation, significantly affected the contents in leachate of most nutrients and metals, except those of N-NH4, Na and Zn. Fertigation resulted in significantly lower N-NO3 losses in comparison with those under CTR. Higher rates of nutrients in fertigation solution resulted in increased N-NO3 content in leachate. The same effect was observed for P, Mg, K, Ca and Cu. The fertigation interval only affected P losses. The lowest P content in leachate was observed in the 2DBF treatment, and the P content in leachate increased as the intervals increased. The fertigation interval did not affect the leaching of any other nutrient. However, a significant difference in leachate content was observed between the CTR with granular fertilizers and fertigation. This effect was observed for N-NO3, K, Ca, Mn and Cu. A significantly higher content of all these nutrients was observed in leachate from the CTR treatment than in that from the fertigation treatments.Fertigation resulted in darker grass leaves in comparison with those under CTR. Higher fertigation rates resulted in darker leaves with higher green hue content than those at lower rates. There were no differences in colour hue in turfgrass fertigated at different time intervals. Turfgrass quality was affected by the fertigation rate and interval. This effect was significant for overall appearance, turf colour and leaf texture, but not for turf cover. The highest mean quality score was obtained at 240NPK, and the lowest was obtained at 60NPK. The optimal fertigation parameters for reduced nutrient losses and high turfgrass quality were calculated to be the 60NPK fertigation level at a fertigation interval of 4.4 days.