N imbalance in 2D maize model

[chporter]

CAIM1501.MZX and CAIM1601.MZX for testing.
There is no 2D NUPTAKE routine for maize.

[chporter]

The imbalance is because of the way we juggle 1D and 2D N variables. There are no 2D routines for root growth or N uptake for maize. When the 1D uptake arrays are split into 2D, it can cause negative soil N values. When this happens, the values are set to zero and there is a loss of N. The N imbalance is exactly equal to these losses.

I don't think it's worth it to put a "bandaid" on the problem. What we really need are 2D roots and N uptake routines.