The Influence Of Applying Nitrogen And Plant Growth Retardant On Growth Of Turfgrass

This paper aimed at the current management of turf mowing and fertilization in theturf maintenance. The research chose cold season turfgrass Kentucky bluegrass (Poapratensis L.), as the test materials, investigating the effect of plant growth retardant Primo(Trinexapac-ethyl) and nitrogen on the growth and physiological characteristics ofturfgrass. The action mechanism of plant growth retardant to inhibit the growth of turfgrass is to reduce turfgrass internodes cell elongation by inhibiting biosynthesis ofGibberellic acid. The study investigated the effect of plant growth retardant in differentnitrogen levels to the height of plant, height increase of turfgrass, clipping yield, flowersheight, chlorophyll content, turf quality, clipping nitrogen content and the total removal ofN, P, K by the turfgrass clipping. The main results are summarized as follows:In spring and autumn, cool season turfgrass grows very quickly. Plant growthretardant in different nitrogen levels showed the difference in inhibiting to the height ofplant, in spring, the maximum inhibition period to the net growth inhibition rates of heightunder 9N, 6N, 3N, 0N reached 52%, 59%, 47%, 52%, while in autumn, this numberwas 67%, 68%, 59%, 78%. Plant growth retardant in different nitrogen levels also hassignificant effect on the clipping yield. In spring, the total clipping yield was significantlyreduced under the four N-level treatments of 9N, 6N, 3N and 0N. The inhibition rates were17%, 18%, 20%, 16%, while in autumn, this number was 21%, 11%, 21%, 25%. So itcan reduce turf mowing frequency, reduce mechanical wear and tear, and cut the cost ofmaintenance.Plant growth retardant in different levels of nitrogen had different effect in differentseason to turf grass quality. In spring, the plant growth retardant has increased turf qualityin the evening under three nitrogen levels of 9N, 6N and 3N. But in autumn under threenitrogen levels of 9N, 6N and 3N, Primo early treatments to reduce turf quality late toimprove turf quality. In spring Primo treatment significantly enhanced turf grasschlorophyll content only under the two nitrogen levels of 9N and 6N. Other treatmentswere not significant compare with the check. The effect to turf grass chlorophyll content ofplant growth retardant in different levels of nitrogen was positively correlated with itseffect to turf grass quality in autumn. In spring, the plant growth retardant in different levels of nitrogen nearly had noeffect to dipping nitrogen content. Primo significantly increased nitrogen content onlyunder the two nitrogen levels of 3N and 0N. More obvious influence was in the autumn,the plant growth retardant significantly increased the nitrogen content of clipping under thethree nitrogen levels of 6N, 3N and 0N.In the study, plant growth retardant was different degrees of reduction of nitrogen,phosphorus and potassium with output under different nitrogen levels which reduced thesoil nutrient loss. The effect was better in autumn than in spring. Mainly because of theautumn of turfgrass dipping inhibition rate higher.In conclusion plants retardant used less could control turfgrass growth significantly;proper use could improve turf quality, reduced frequency of mowing, reduced nutrient lossand lower maintenance costs.