水肥耦合对楸树苗木生长和养分状况的影响

目的探究不同水肥条件下楸树苗木生长及养分状况，确定楸树苗木合理水肥管理措施。方法本文以楸树幼苗为试验材料，采用双因素完全随机试验，设置3个水分梯度(30%饱和持水量(FWC)、50%FWC、70%FWC)，和4个施肥量(T1(氮0g，磷0g，钾0g)、T2(氮2g，磷1g，钾1.5g)、T3(氮4g，磷2g，钾3g)、T4(氮6g，磷3g，钾4.5g))，通过盆栽试验研究了不同水肥处理对楸树苗木生理生长的影响，并探讨了楸树苗木生长及养分吸收的关系。结果水肥耦合对楸树苗木的形态指标交互作用不显著，苗高、地径、生物量均随水分梯度的增加而降低，在水分梯度为30%FWC时最好；随施肥量的增加呈先增加后降低，均在T3处理达到峰值。苗木养分在T3处理时达到奢养状态，此时苗木的苗高、地径、生物量及养分含量最高，再增加施肥会对苗木产生毒害作用，即苗木养分质量分数还在增加但形态指标和养分含量已开始降低。水肥耦合对楸树苗木养分质量分数和养分含量有一定的交互作用，其养分含量均随施肥量的增加而增加，在T3处理处达到最大；在水分含量为30%FWC时，施肥对楸树苗木有较好的促进作用，T3、30%FWC处理更有利用苗木养分的吸收和利用。结论水分梯度和施肥量对苗木生长和养分状况的作用证实，水肥耦合对苗木的质量有一定的提升，30%的饱和持水量和T3处理(氮4g，磷2g，钾3g)结合对楸树苗木育苗效果最好。 

Coupling effects of water and fertilizer on seedling growth and nutrient status of Catalpa bungei

Objective] Water and fertilizer are two key factors to promote plant growth, thus, it is important to study their coupling effects on growth and nutrient status of Catalpa bungei seedlings. Method]The pot experiment with Catalpa bungei seedlings in three different water levels (30% ,50%and 70% saturated water content(FWC)) with four fertilization levels of T1(N 0 g,P 0 g,K 0 g), T2(N 2 g,P 1 g,K 1. 5 g), T3(N 4 g,P 2 g,K 3 g), T4(N 6 g,P 3 g,K 4. 5 g) was conducted to study the coupling effects of water and fertilizer on growth, nutrient absorption and fertilizer utilization. Result] The interactive effects of water and fertilizer coupling on morphological indexes of Catalpa bungei seedlings were not significant. Root collar diameter, height, and biomass of seedlings decreased with rising water level, reaching the top at 30% saturated water content, but firstly increased and then decreased with increasing fertilization level, reaching peak at T3 fertilization level. The nutrient content of seedlings reached a luxury nutrient state at T3 treatment, meanwhile seedling height, root collar diameter, biomass and nutrient content of seedlings were the highest. If more fertilizers were applied on seedlings, it would occur toxic effects. Since at T3 treatment, although the nutrient concentration of seedlings was increasing, the morphological indexes and nutrient content decreased. There were interactions of water and fertilizer coupling effects on nutrient concentration and nutrient content of Catalpa bungei seedlings. Nutrient content rose with increasing fertilizers, and reached the peak under T3 treatment. When water content was 30% FWC, fertilization had a greater promotion for seedlings of Catalpa bungei. Conclusion] It proves that water and fertilizer coupling effects promote the quality of seedlings. Furthermore, 30% FWC and T3 treatment was the best combination for cultivating seedlings of Catalpa bungei.