图4. 不同养分水平下施用有机肥对氮肥利用率的影响
点和误差线分别代表响应比及其95%的置信区间,如果误差线没有跨越零线表示处理和对照存在显著差异;括号内的数值、百分数及字符分别代表样本数、施肥响应百分数和单位。SOM：土壤有机质含量,pH：土壤酸碱度,AP：土壤速效磷含量,TN：土壤全氮含量,AN：土壤有效氮含量,AK：土壤速效钾含量

Fig. 4. Effect of applying organic fertilizer on NUE under different nutrient levels
Dots with error bars denote the overall mean response ratio and 95% CI, respectively. The 95% CI that do not go across the zero line mean significant difference between treatment and control. The value and percent in parentheses represent independent sample size and percent response to fertilization, respectively. SOM: soil organic matter content, pH: soil pH, AP: soil available phosphorus content, TN: soil total nitrogen content, AN: soil available nitrogen content, AK: soil available potassium content