Below-harvest biomass and N2 fixation in grass-clover at different cutting frequencies

Summary

The below-harvest nitrogen accumulating in stubble, stolons and roots is an important com-ponent in the N balance and the potential N losses in grass-clover cropping systems. The effects of cutting frequency on the total dry matter, total nitrogen and N2 fixation, including contributions from below-harvest production, were studied. In a greenhouse experiment with red and white clover plants, cutting reduced the above-ground dry matter production by 56-62% and the below-ground by 68-73%, compared to uncut plants. Similarly, in a two-year field study with ryegrass-white clover, simulated grazing reduced the harvested dry matter production by 6-19% and the below-harvest, i.e., stubble, stolons and roots, by 20-35% com-pared to normally mowed grass-clover. Thus, the results from both the greenhouse and the field study indicated that below-ground or below-harvest production was more affected by cutting or simulated grazing than harvested production.