The Influence Of Applying Nitrogen And Plant Growth Retardant On Turfgrass

The range of turf application was very wide. Such as sports turf with high maintenance level, ornamental turf with middle maintenance level and eco-turf with low maintenance level. Plant growth retardants could reduce turf growth and improve turf quality, but varieties and environment would affect PGRs effect.The two years replicated experiment chose cold season turfgrass Kentucky bluegrass (Poa pratensis L.), as the test materials, investigating the effect of plant growth retardant (Trinexapac– ethyl and Paclobutrazole) and nitrogen on the growth of turfgrass. The action mechanism of the two plant growth retardant to inhibit the growth of turf grass is to reduce turfgrass internodes cell elongation by inhibiting biosynthesis of Gibberellic acid. The study investigated the effect of plant growth retardant in different nitrogen levels to the vertical growth of plant, clippings yield, leaf width, leaf thickness, chlorophyll content, water consumption, soluble protein and soluble sugar. The main results are summarized as follows:ⅠPlant growth retardants reduced vertical growth by and clippings yield by among the four nitrogen levels, Trinexapac– ethyl reduced vertical growth by 30.1%, and reduced clippings yield by 16.5%; Paclobutrazole reduced vertical growth by 41.2%, and reduced clippings yield by 25.8%. So the cost decreased as the mowing frequency reduced.ⅡPlant growth retardants reduced water consumption as antitranspirants among the four nitrogen levels, Trinexapac– ethyl reduced water by 3.1%, Paclobutrazole reduced water by 6.1%. PGRs not only saving water and saving cost, but also reduced the loss ratio of fertilizer and pesticide, the pollution reduced as the loss ratio decreased.ⅢPlant growth retardants increased the content of chlorophyll among the four nitrogen levels, Trinexapac– ethyl increased the content by 7.7%, Paclobutrazole increased the content by 10.6%. So PGRs would improve turf green color without nitrogenous.ⅣTrinexapac– ethyl made leaf widening by 10.7% and thickening by 22.1%, Paclobutrazole made leaf widening by 11.4% and thickening by 24.9%. Trinexapac– ethyl increased soluble protein content by 11.7% and soluble sugar content by 13.9%; Paclobutrazole increased soluble protein content by 11.8% and soluble sugar content by 15.5%. PGRs made turf resistance stronger, reduced the amount of insecticide and fungicide, so PGRs would save money and reduce pollution. ⅤThe effects of plant growth retardants had differences in different years and different seasons. PGRs had stronger effect in autumn than in spring, and had better effect in 2006 spring than in 2007 spring, which related to environmental weather. The effect was stronger as the temperature was higher.ⅥThe plant growth retardants had faster results and shorter duration under high-nitrogen fertilizer, the plant growth retardants had lower results and longer duration under high-nitrogen fertilizerIn a word, plant growth retardants would reduce cost, save water and decrease pollution. Before large-area application, a small-scale experiment would be made, in order to determine application rate and application date.