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Fig. 6. Effect of management treatments: (i) barley followed by corn under no-tillage (Barley-NT), (ii) barley followed by corn under a spring plowing and secondary tillage operation (Barley-CT), (iii) barley under-seeded with red clover that was plowed down in the following spring and plots planted to corn (Barley + RC-CT) on the ratio between Ni and Nc concentration in the aerial dry matter at three growth stages and its variation with organic C content. The solid horizontal line indicates the minimum N concentration in the aerial dry matter for the maximum growth (i.e., Nc). Other lines were generated using the regression models given in Table 5.
