Available P differed among the herbicide treatments. Averaged
across crop rotations and soil depth, soil P concentration increased
with glyphosate only treatments (TRT 1 & TRT 2). Soil P was not different
between the alternative herbicide treatments (Fig. 3a). Available
soil P concentration was affected by sampling depth and crop rotation
interaction (P = 0.014). Averaged across herbicide treatments, soil P
in the top 7.5 cm with CC production (97 mg kg−1) was 26% greater
than that of CS (77 g kg−1, Table 3). The difference in available P between
the crop rotations was not significant below 7.5 cm.