Figure 2.

Limestone application significantly increased soil pH during a maize–wheat rotation in northern China after 3, 9, 12, and 27 months. The theoretical soil pH of each treatment, calculated by the liming rate model, was represented by corresponding dashed reference lines. The means ± standard deviation (n = 3) were shown. Statistical differences were denoted by lowercase letters using Tukey’s test at a significance level of p < 0.05.