Figure 2.

Average (±SE) NO₃-N and NH₄-N concentrations extracted from soil resin bags (15 cm depth) from November 2013 until October 2014 in the organic cover crop treatments (A,B), the organic N-fertilizer treatments (C,D), and the conventional N-fertilizer treatments (E,F). Asterisks indicate points in time where significant effects between treatments were observed. Note that scales differ across graphs (A,C vs. E). Cover crops were terminated and fertilizers were applied on 20 and 28 May 2014, respectively. Cover crop species are indicated in the legends, where 0 N = no applied fertilizer, Organic N = 168 kg ha⁻¹ organic fertilizer, fertilizer N-credit = 56 kg ha⁻¹ organic fertilizer+additional hairy vetch, Urea N = 168 kg ha⁻¹ urea+urease inhibitor.