The changes in shoot biomass were similar to those of LAI during the three experimental years (Fig. 4). The shoot biomass accumulated faster under PM and PSM treatments than under SM and CK treatments during the early stages of maize development in all three experimental years. It was also consistently and significantly greater on PM and PSM plots than on SM and CK plots in 2008 and 2009, during the whole growing season. However, in 2007, shoot biomass was higher on the SM plots than on the other treatment plots at the last two sampling dates. These findings are consistent with the observations of LAI dynamics.