N distribution in maize plant as a marker for grain yield and limits on its remobilization after flowering

To determine the relationship between specific leaf N (SLN) and grain yield or its components in commercial maize hybrids in the US Corn Belt, three studies were conducted in 2010 and 2011. Leaf area index at flowering ranged from 3 under low to 5.6 at normal soil N. At flowering, 70% of the vegetative N was sequestered in the leaves, 22% in stalk and 8% in leaf sheaths, whereas the respective numbers for dry mass were 34, 50 and 16%. Highest grain yield was obtained at an SLN of 1.5. N stress affected both kernel number and kernel mass per plant. Regardless of the initial amount of leaf N at flowering, similar to 65% was remobilized by maturity. Under normal soil N, leaf N at flowering contributed at most 40% to the grain N. An increase in N storage capacity of the leaves would improve stability of hybrid grain yield as well as reduce loss of N from the soil by leaching and run-off.