Effect Of Nitrogen Fertilizer On Growth Performance And Green Period Prolonging Of Cold-season Turfgrass

Effects of different nitrogen application rates and frequencies on growth performance, cold resistance and turf quality of mixed cool season turfgrass (Kentucky bluegrass + Perennial ryegrass + Red fescue) between late green stage and regreening stage were studied through field experiments. The nitrogen fertilizer application rates (N basis) were designed as 35g/m2, 30 g/m2, 25g/m2, 20g/m2, 15g/m2 and 10g/m2 per year (N35,N30,N25,N20,N15,N10), the application frequencies were desighned as 2, 4 and 6 (T2, T4, T6). The results showed as follows:1. Compared with control, the application of nitrogen fertilizer significantly postponed the beginning date of withered and yellow period of turfgrass from 7 days to 22 days. And the postponed days increased at the beginning and then decreased later along with the increase of nitrogen application rate. The best treatment was N25T6, which postponed the beginning date of withered and yellow period by 22.7 days. It could be postponed by increasing nitrogen application frequency as well and the difference among all treatments was significant (P<0.05). The regreening date was the earliest under the treatment N30T6 and it was aheaded by 21.7 days. Within whole growth stage, N25T6 and N30T6 showed the most significant effect on prolonging the green period (43.0 days and 42.7 days respectively).2. Nitrogen application significantly enhanced the chlorophyll contents under all treatments, but the impact of fertilization was not significant while the application rate was over 20g/m2 (P>0.05). The variation of chlorophyll content could be reduced by increasing nitrogen application frequency. N20T6 and N25T6 showed the best performance for improving the colour of turfgrass (the chlorophyll content was more than 2.00g/mg·FM).3. In the withered and yellow period, malondialdehyde content of turfgrass decreased with the increase of nitrogen application frequency but contrary results were abtained in regreening period, in which MDA content decreased along with time. The MDA content was the highest (2.56×10-2umol/g·FM, on 18th March 2005) under N35T6. and it was the lowest(0.89×10-2umol/g·FM, on 18th 2005) under N20T2.4. The impact of excessively high or low nitrogen application rates on the catelase activity was negative. Among all treatments, the catelase activity was the highest under N20...