Sweet corn nitrogen accumulation, leaf photosynthesis rate, and radiation use efficiency under variable nitrogen fertility and irrigation

Virtually no information exists on the response of sweet corn (Zea mays L. saccharata) to nitrogen fertility and irrigation treatments in terms of leaf nitrogen accumulation and the consequent impact on leaf CO2 assimilation rate and on crop growth as measured as radiation use efficiency (RUE). A two-year field experiment was undertaken in which a sweet corn cultivar was subjected to all combinations of five nitrogen fertility and three irrigation treatments. Leaf photosynthesis measurements were made at stages of 7–9 leaves, tasseling, silking, blistering, and milking. Leaf nitrogen per unit area was also measured at these five stages plus two additional stages before and after the five core measurements. Total nitrogen and plant mass was accumulated at the seven stages to track total nitrogen accumulation and to calculate RUE. The overall patterns in the measured variables were similar to those reported for field maize. However, leaf nitrogen per unit area for sweet corn under optimum conditions was greater than reported for field maize. The higher leaf nitrogen per unit area in sweet corn did not, however, result in greater leaf photosynthesis rates and RUE than reported for field maize. The results of these unique observations on sweet corn indicate the possibility of greater nitrogen storage in sweet corn leaves that is not directly linked with photosynthesis and carbon accumulation.