Effects Of Clipping Height On Growth Of Cleistogenes Songorica

Cleistengenes songorica is an important native forage plant species in the Northwest and North desert grasslands of China and it also has some value for turf grass breeding. The effects of clipping on C. songorica were studied in plots in the Alax rangeland and Zhangye pasture in 2004-2005. Additional pot and laboratory tests were also carried out. In order to understand the effects of different stubble heights on the growth of C. songorica, herbage dry matter yields, content of total nonstructural carbohydrate and chlorophyll, numbers of tillers together with leaf width and roots were studied.In three experiments, the total herbage dry matter yields of treatments with 3, 5, 7, or 10 cm stubble were significantly higher than that of the unclipped control, and the total herbage dry matter yields of treatments with 5 cm and 7 cm stubble were higher than those of other treatments. In the Alax rangeland, the total herbage dry matter yields of the treatment with 5 cm stubble was 21.2% and 37.6% higher compared with that of 3 cm and 10 cm treatments, respectively, while yield of the 7 cm stubble was 15.42% and 31.10% higher respectively. In Zhangye pasture, the total herbage dry matter yields of the treatments with 7 cm and 10 cm stubble was reduced by 33.8% and 33.6% respectively compared with the 5 cm treatment. Compared with the control of no clipping, the total herbage dry matter yields of treatments with 5, 7, and 10 cm stubble was increased by 260%, 140%, 130%, respectively. In pot trials, the total herbage dry matter yields of treatments with 5 cm and 7 cm stubble increased by 21.3% and 35.4% respectively compared with the 3 cm treatment. Compared with the control, the total herbage dry matter yields of treatments with 3, 5, 7, and 10 cm stubble increased by 110%, 155%, 185%, and 146%, respectively.There were no significant differences in the water soluble carbohydrate content of the different clipping treatments in three experiments. There were significant (P<0.05) differences in the content of reducing sugar between treatments with 3, 5, and 10 cm stubble and that of the control. This showed that the effects of clipping on reducing sugar were stronger than on water soluble carbohydrate so reducing sugar content may be a good indicator of the effects of clipping on C. songorica.The treatments with 5 cm and 7 cm stubble increased the amount of water soluble carbohydrate per square metre compared with the control and other treatments. Compared with the 3 cm treatment and the control, the water soluble carbohydrate yield of 7 cm stubble was increased by 36% and 47% respectively in the Alax rangeland and by 45% and 58% respectively in pots. The content of water soluble carbohydrate of aboveground plant parts was higher than that of roots, showing that water soluble carbohydrates mainly accumulate aboveground. The dry matter yields of roots, the diameter and length of rootstogether with the content of nonstructural carbohydrate were significant lower than those of the controls and they also decreased with lower stubble heights. This showed that clipping could inhibit the growth of C. songorica, and it is important to consider the effects of clipping on roots.The clipping treatments did not significantly improve the number of tillers. In pot experiments there were no significant differences (P>0.05) between treatments in the chlorophyll content of plants. The leaves of C. songorica became narrower if clipping frequency increased, and the value for use as a turf grass was increased by clipping.In conclusion, the optimum clipping pattern for C. songorica of 5-7 cm stubble significantly increased yields of dry matter, water soluble carbohydrate yields and content of reducing sugar but did not affect the content of water soluble carbohydrate or chlorophyll, or the number of tillers.