Shoot and grain dry weight (DW; g m−2) and total N, P and K contents (g m−2) of different maize varieties at silking in 2008 and at silking and maturity in 2009.

BMY and JHH are early senescing varieties released in the 1950s; ZD2 and TK5 are two intermediate senescing hybrids released in the 1970s; ND108 and ZD958 are two currently popular stay-green hybrids. Values in rows followed by different letters represent significant differences between varieties (PShoot and grain dry weight (DW; g m−2) and total N, P and K contents (g m−2) of different maize varieties at silking in 2008 and at silking and maturity in 2009.