Fig. 5. Changes in mineral N (NH₄–N plus NO₃–N, kg ha^-1) at fallow harvest compared with mineral N at planting in different soil layers as affected by (a) monocrop fallows and crop systems and (b) mixed fallows, natural fallow, and calliandra monocrop fallows at Nyabeda, western Kenya. Standard error of the difference in means (SED) bars are for comparison of total mineral N values between treatments means.