不同灌溉方式下甘蔗光合特性

Photosynthetic characteristics of sugarcane under different irrigation modes

光合作用是植物干物质积累的重要过程,作物产量主要通过光合作用实现。为比较不同灌溉模式下甘蔗光合特性差异,探明其主要影响因素,以柳城05-136号为试验甘蔗品种,于2015年3月-12月在广西崇左市江州区试验基地开展6种灌溉模式甘蔗净光合速率及主要环境因子的田间观测。结果表明:地埋滴灌甘蔗净光合速率最高,平均值为29.23μmol/m2·s,无灌溉最低,为18.53μmol/m2·s,地埋滴灌分别比无灌溉、管灌、喷灌、微喷和地表滴灌高57.74%、23.54%、12.68%、9.68%和2.56%,灌溉能显著提高甘蔗的光合速率(P<0.05)。通径分析结果显示,土壤含水率、空气温度和土壤肥力是影响甘蔗净光合速率的主要环境因子,但各灌溉模式之间主要影响因子存在差异,无灌溉和地埋滴灌土壤肥力的影响较为显著,地表滴灌则是土壤含水率和速效氮的影响较为显著,管灌模式主要影响因子为土壤速效钾和空气温度,而喷灌和微喷模式的主要影响因子均为土壤含水率和空气温度。采用地埋滴灌模式更有利于研究区域甘蔗净光合速率的提升,此外,针对不同灌溉模式的主要影响因子进行合理调控可有效提高甘蔗净光合速率,从而提高甘蔗产量。

Efficient, water-saving irrigation modes are commonly used in the sugarcane fields of latosolic red soils in the Guangxi Zhuang Autonomous Region, China. This research studied the effects of different irrigation treatments on photosynthetic characteristics of sugarcane. Because photosynthesis is an important process in plant dry matter accumulation, this research has implications for the development of high-efficiency cultivation methods that produce high yields of sugarcane. We planted the sugarcane cultivar Liucheng 05-136 under 6 types of irrigation modes： no irrigation, subsurface drip irrigation, surface drip irrigation, pipe irrigation, sprinkler irrigation, and micro sprinkler irrigation. Field measurements of net photosynthetic rate and related environmental factors（soil water content, soil temperature, air temperature, relative air humidity, soil organic matter, soil available nitrogen, soil available phosphorus, and soil available potassium content） were conducted at the Sugarcane Efficient Water-saving Irrigation Test Base in Chongzuo City from March to December, 2015 for different growth phases of sugarcane（tillering stage, early, peak and late stages of elongation, and maturation stage）. Additionally, the differences in net photosynthetic rate of sugarcane under different irrigation modes were investigated with a multiple comparison method, and the relationship between environmental factors and net photosynthetic rate was analyzed using stepwise regression and path analysis. Results showed that the mean net photosynthetic rates of sugarcane under no irrigation, subsurface drip irrigation, surface drip irrigation, pipe irrigation, sprinkler irrigation, and micro sprinkler irrigation were 18.53, 29.23, 28.50, 26.65, 25.94 and 23.66 μmol/（m^2·s）, respectively. Net photosynthetic rate was the lowest under the no irrigation mode, while the highest value appeared under the subsurface drip irrigation mode, which was 57.74%, 23.54%, 12.68%, 9.68% and 2.56% higher than that of no irrigation, pipe irrigation, sprinkler irrigation, micro sprinkler irrigation and surface drip irrigation, respectively. Therefore, irrigation can significantly improve sugarcane photosynthetic rate（P〈0.05）. Path analysis results showed that soil water content, air temperature and soil fertility were the main environmental factors influencing sugarcane net photosynthetic rate on the whole, but some differences existed between irrigation modes. Soil fertility was a key variable for photosynthetic rate under no irrigation and subsurface drip irrigation, while soil water content and soil available nitrogen content had significant effects on photosynthetic rate under surface drip irrigation. In the case of pipe irrigation, soil available potassium and air temperature were the major factors. For sprinkler and micro sprinkler irrigation, the main factors were soil water content and air temperature. It may adjust the influence of irrigation treatments on photosynthesis through the regulation of environmental factors（air temperature and humidity, and soil physical and chemical properties）. In addition, each factor mutually acts to promote or restrain the photosynthesis process, showing a comprehensive effect. In terms of soil water content, its influence on photosynthesis was reflected in the effect on absorption of nitrogen, phosphorus and potassium nutrient elements for sugarcane under no irrigation, subsurface and surface drip irrigation modes. Comprehensive analysis showed that the subsurface drip irrigation treatment effectively improved sugarcane photosynthesis. Subsurface drip irrigation will be more suitable for the cultivation of sugarcane in the latosolic red soils in the Guangxi Zhuang Autonomous Region. Furthermore, according to the different irrigation modes, ensuring favorable control of soil water content in combination with other main influencing factors, can further improve sugarcane net photosynthetic rate, and consequently increase the yield of sugarcane.