Effects Of Nitrogen Fertilizer And Cutting On Physiological And Ecological Characteristics,Yield And Quality Of Pennisetum Purpureum Cv.Guimu-1

This experiment was conducted from2011to2012in Huanjiang observation and research station of karst ecosystem, Chinese academy of sciences. An orthogonal experiment design was used to study the effects of nitrogen fertilizer and cutting on physiological and ecological characteristics, yield and quality of pennisetum purpureum cv. Guimu-1. The main results were as follows.1. The effects of nitrogen fertilizer and cutting on photosynthetic characteristics of pennisetum purpureum cv. Guimu-1Nitrogen fertilizer had significant control on photosynthetic characteristics of pennisetum purpureum cv. Guimu-1. Fertilizing1000or1500kg·hm-2·a-1obviously improved the peak of net photosynthetic rate and declined the noon break phenomenon of photosynthesis. And with1000or1500kg·hm-2·a-1nitrogen supplying, carboxylation efficiency and maximum photosynthetic rate significantly increased, while photorespiratory rate at a lower level. Nitrogen fertilizing rate was1000or1500kg·hm-2·a-1, after twice or3times cutting and the cutting intensity was5or15cm, the apparent quantum yield, light saturation point and maximum photosynthetic rate of pennisetum purpureum cv. Guimu-1were the highest or higher, and the chlorophyll content maintained at a higher level, the photosynthesis of grass obviously enhanced.2. The effects of nitrogen fertilizer and cutting on growth and yield of pennisetum purpureum cv. Guimu-1Nitrogen fertilizer and cutting had extremely significant effects on height and tillering number of pennisetum purpureumcv. Guimu-1. Nitrogen fertilizing rate of1000or1500kg·hm-2·a-1could significantly promote the growth of plant height and tillering. The combination with3or4cutting times and5or15cm cutting intensity could significantly improved the tillering ability of the grass. While along with an increase in cutting frequency, the height of regenerated grass performed the trend of declining.Nitrogen fertilizing rate and cutting intensity had extremely significant and significant effects on yield of pennisetum purpureum cv. Guimu-1. The combination with1000or1500kg·hm-2·a-1nitrogen fertilizing rate and5or15cm cutting intensity had a significantly effect of increasing production of the grass.3. The effects of nitrogen fertilizer and cutting on quality of pennisetum purpureum cv. Guimu-1Nitrogen fertilizing rate had significant and extremely significant effects on the content of crude protein, crude fat and crude fiber. The fertilization level with best effect was1000kg·hm-2·a-1. Cutting frequency had extremely significant effects on each nutrient content, and with4times cutting per year, the content of crude protein was significantly increased, while the content of crude fiber was relatively low. Cutting intensity only significantly affected on the content of crude fat. The best cutting intensities was15cm.Nitrogen fertilizing rate and cutting intensity had significant effects on crude protein yield of pennisetum purpureum cv. Guimu-1. The combination with1000kg·hm-2·a-1nitrogen fertilizing rate, and15cm cutting intensity had the highest crude protein yield every year.4. The effects of nitrogen fertilizer and cutting on soil ecologyWith an increase in nitrogen fertilizing rate, the pH value of soil performed the trend of declining. After nitrogen fertilizing, the content of soil available phosphorus and available kalium significantly increased, and alkali-hydrolyzale nitrogen content also increased to a certain extent. The fertilization level with best effect was1000or1500kg·hm-2·a-1. Cutting frequency significantly affected on the content of soil total kalium and available kalium. With3times cutting, the content of soil total kalium and available kalium were all the lowest. Cutting intensity had significant effects on the content of soil organic matter, available phosphorus, total kalium and available kalium. With35cm cutting, soil organic matter content was the highest, and15cm cutting took the second place. The best cutting intensities for available phosphorus and available kalium content were all15cm.Nitrogen fertilizing rate and cutting frequency had extremely significant effects on soil microbial biomass nitrogen and microbial biomass phosphorus. With fertilizing500kg·hm-2·a-1, microbial biomass nitrogen and microbial biomass phosphorus were all highest. With3or4times cutting, microbial biomass nitrogen was significantly increased, while2times cutting had a significantly promoting role in biomass phosphorus. Cutting intensity only significantly affected on microbial biomass nitrogen, and the best cutting intensity was35cm,15cm cutting took the second place.Based on the comprehensive analysis of this research, under the combination with1000kg·hm-2·a-1nitrogen fertilizing rate,4times cutting per year, and15cm cutting intensity, pennisetum purpureum cv. Guimu-1in the karst region was in high yield and good quality, and this combination was good for soil available nutrients, too. Therefore, this management mode could be used as the preferred mode for grass planting in the karst region.