Abstract: In order to explore the influence of potassium fertilizer types and dosage on cold resistance of alfalfa,this study took ‘Gibraltar’ as the test alfalfa (Medicago sativa),and adopted two-factor randomized block design to study the application of different potassium fertilizer (potassium sulfate and potassium chloride) and different application rates (0,50,100,150,200 kg·hm^-2 K₂O) on root and neck of alfalfa in overwintering period (4℃,-20℃),and the changes of the contents of soluble protein (SP) and malondialdehyde (MDA). The results showed that there was no significant difference in MDA and SP contents and POD,SOD and CAT activities in overwintering roots and necks of alfalfa under 4℃ temperature treatment when treated with different potassium fertilizer and different application rates. However,after freezing at -20℃,the contents of MDA decreased and SP increased,the activities of POD,SOD and CAT increased,and the ability to adapt to low temperature environment became stronger when treated with different potassium fertilizer and different application rates,and potassium sulfate was stronger than potassium chloride. When both potassium fertilizers were treated with 150 kg·hm^-2 (K₂O) potassium fertilizer,the contents of MDA were the lowest,the activities of POD,SOD and CAT were the strongest,and the contents of SP were the highest,which indicated that alfalfa had the least injury degree and the strongest cold resistance protection ability. Therefore,the application of K₂SO₄ 300 kg·hm^-2 in autumn in Horqin Sandy Land is conducive to the safe overwintering of alfalfa.

Key words: Potash fertilizer, Alfalfa, Freezing stress, Antioxidant properties

摘要： 为探究钾肥种类及用量对苜蓿(Medicago sativa)抗寒性的影响,本研究以‘北极熊’为供试紫花苜蓿品种,采用二因素随机区组试验设计,研究了秋季施用不同钾肥(硫酸钾和氯化钾)及不同施用量(0,50,100,150,200 kg·hm^-2 K₂O)对越冬期苜蓿根颈在不同温度(4℃,—20℃)处理下抗氧化酶[过氧化物酶(peroxidase,POD),超氧化物歧化酶(superoxide disimutase,SOD),过氧化氢酶(catalase,CAT)]活性和可溶性蛋白(soluble protein,SP)、丙二醛(malondialdehyde,MDA)含量变化的影响。结果表明:在4℃温度处理下,不同钾肥种类和施肥量处理中,苜蓿越冬根颈中MDA和SP含量及POD,SOD,CAT活性均无显著差异;但经—20℃低温冷冻后,不同钾肥种类和施肥量处理下,苜蓿越冬根颈中MDA含量下降,SP含量增加,POD,SOD,CAT活性增强,适应低温环境能力变强,且硫酸钾效果强于氯化钾;两种钾肥均在150 kg·hm^-2(K₂O)钾肥处理下,MDA含量最低,POD,SOD,CAT活性最强,SP含量最高,表明苜蓿受伤程度最小,抗寒保护能力最强。因此,在科尔沁沙地秋季施用300 kg·hm^-2K₂SO₄有利于苜蓿安全越冬。

关键词: 钾肥, 苜蓿, 冷冻胁迫, 抗氧化特性