科尔沁沙地苜蓿-禾草混播增产的生理生态机制

Horqin Sandy Land is an important production base of cattle and sheep in northern China,establishing alfalfa - grass mixed grassland in this region has important significance in development of animal husbandry and ecological restoration. Our previous work found that, alfalfa - grass mixed combinations and fertilization have significant effects on pasture yield under irrigated conditions, but its physiological and ecological mechanism of affecting yield formation is unclear.We will study effects of alfalfa-grass mixed combinations,mixture Proportion and fertilizer on pasture yield by using methods of four kinds of grasses and alfalfa mixed combination experiment and fertilization experiment , and to explore the relationship between yield of alfalfa-grass mixed grassland and pasture photosynthetic efficiency（individual and group photosynthetic efficiency，chlorophyll content, chlorophyll fluorescence parameters, population and leaf area index, etc.） efficiency of carbon and nitrogen metabolism(content of different type sugar and nitrogen and its key enzyme activity), capacity of membrane lipid antioxidant(SOD,POD,CAT activity and MDA content), interspecific compatibility (interspecific competition,relative yield total, dry weight of root, shoot and leaves, and regeneration rate, etc), grass soil interaction efficiency (soil enzyme activity , contents of soil carbon and nitrogen, soil moisture content and soil bulk density, etc.). Clarifying physiological and ecological mechanisms of alfalfa – grass mixture on yield increase in sandy land and providing the theoretical basis and technical support for highly effective cultivation and sustainable use of alfalfa – grass mixed grassland in Horqin Sandy Land.

科尔沁沙地是我国北方重要的牛羊生产基地，建植苜蓿-禾草混播草地对当地养殖业发展和生态保护具有重要意义。我们前期工作发现，在灌溉条件下，苜蓿-禾草混播组合和施肥对草地产量影响显著，但对其生理生态机理尚不清楚。我们将用苜蓿与4种禾草混播组合试验和施肥试验方法，研究科尔沁沙地苜蓿-禾草混播草地产量对草种组合、混播比例和氮磷钾肥施加的响应规律；探索混播草地产量与牧草光合效率（个体与群体光合效率、叶绿素含量、叶绿素荧光参数、种群与群落叶面积指数等）、碳氮同化效率（不同类型糖和氮含量及其关键酶活性）、膜脂抗氧化能力（SOD、POD、CAT活性和MDA含量）、种间相容性（种间竞争力、相对产量总和、根、茎、叶生物量和再生速率等）以及草土互作效率（土壤酶活性、土壤养分和水分含量等）之间的关系，阐明沙地苜蓿-禾草混播增产的生理生态机制，为科尔沁沙地苜蓿-禾草混播草地高效栽培和持续利用提供理论依据和技术支持。

科尔沁沙地是我国北方重要的牛羊生产基地，建植苜蓿+禾草混播草地对当地养殖业发展和生态保护具有重要意义。采用紫花苜蓿+无芒雀麦、紫花苜蓿+通草1号虉草和紫花苜蓿+垂穗披碱草混播组合试验（以豆禾1:1，1:2，2:2和2:1间行混播）和紫花苜蓿+无芒雀麦（以豆禾1:2，2:2间行混播）草地氮磷钾组合施肥试验，研究科尔沁沙地苜蓿-禾草混播增产的生理生态机理。研究结果表明：苜蓿+无芒雀麦和苜蓿+虉草组合三年平均禾豆总产量（8.18~8.28 t/hm2）及禾草产量比（18.70%~20.88%）极显著高于苜蓿+垂穗披碱草组合（7.34 t/hm2，13.64%），苜蓿+虉草组合产量可持续指数（0.77）显著高于苜蓿+无芒雀麦（0.66）和苜蓿+垂穗披碱草（0.67）组合，表明苜蓿+虉草组合产量可持续性较好。豆禾1:1和2:1混播禾豆总产量较高，产量稳定性较好，但禾草产量比较低（9.67%~14.69%），混播禾草组分稳定性较差。豆禾1:2混播禾草产量比较高（26.02%），混播禾草组分稳定性和产量可持续性较好，但禾豆总产量较低（6.16 t/hm2）。播种当年，苜蓿与禾草1:1混播禾豆总产量高于单播苜蓿产量，第二年后所有组合的混播总产量均低于单播苜蓿产量，但均高于单播禾草产量。建植第2~3年豆禾2:2混播禾草种间竞争力显著高于其他处理。适量的氮磷钾肥组合能显著提高混播牧草产量，氮肥效果大于磷钾肥。禾草与苜蓿氮磷钾素偏生产力和吸收率均随氮磷钾素水平增加而降低，吸收量呈先增加后降低趋势。豆禾2:2混播苜蓿及禾豆NPK偏生产力、吸收量、吸收率以及禾草氮素利用率、苜蓿钾素利用率显著高于1:2混播。综合考虑牧草产量、品质、群落稳定性及养分利用效率等因素，苜蓿+无芒雀麦或苜蓿+通草1号虉草2:2间行混播，全年施氮140 kg/hm2，磷（P2O5）100 kg/hm2，钾（K2O）120 kg/hm2，在返青期施40%，头茬和二茬草后各施30%较适宜，禾豆总产量可达到11.12 t/hm2。本研究成果丰富了苜蓿-禾草混播理论与技术，对苜蓿-禾草混播草地高效栽培具有重要的指导意义。