Nitrogen Partitioning in Maize during Ear Development

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Abstract
The partitioning of N during the grain‐filling period of maize (Zea mays L.) was studied under field conditions at differing levels of fertilizer. Two hybrids with differing leaf‐canopy senescence, B73Ht × LHI05 (rapid) and B73Ht × Va35 (slow), were grown with two rates (67 and 257 kg ha−1). Separate plants were supplied with 15N the 14‐leaf stage (VI4), antbesis, or 22 d after anthesis, and the subsequent patterns of 15N partitioning were followed. Independent of time of application, hybrid, or N fertility, ⊄45% of the 15N applied was absorbed within 3 d. Three days after the V14 treatment, the stalk contained 50% of the absorbed 15N, suggesting that it acts as a major sink for N during vegetative growth. With later applications, the 15N was predominantly partitioned to the ear. Although absorption of total N from soil continued during the grain‐filling period, there was significant remobilization of N from vegetative organs (60 to 85% of the total N present at anthesis) to the ear. Leaves and stalk each contributed 45% of total N remobilized into the ear, and 10% was contributed by the roots. Loss of N from the stalk was initiated before anthesis, whereas it began around anthesis with leaves and roots. The results indicate the important role of the stalk in providing N for kernel development. Both N fertility and hybrid influenced the rate of N remobilization from vegetative tissues.
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