Figure 1.
Potential nitrifying enzyme activity (NEA) measured in the eight soils from September 2009 to October 2010 (A), and the difference observed in the amplitude of variation in sandy (Δtsandy = 0.14 μgN h− 1 gdw− 1 ± 0.04), and in clayey soils (Δtclayey = 0.39 μgN h− 1 gdw− 1 ± 0.08) over time (B), calculated by subtracting lower from higher values. Soil names are: B, Buinen; V, Valthermond; D, Droevendaal; W, Wildekamp; K, Kollumerwaard; S, Steenharst; G, Grebbedijk; and L, Lelystad. Bars are SE (n = 4). Black symbols: sandy soils; gray symbols, clayey soil.