WATER, NITROGEN AND WEED STRESS IN FIELD CORN (ZEA MAYS L.) : SHOOT GROWTH AND DEVELOPMENT

EpHRATH J. E., ALM D. M., HESKETH J. D. and HUCK M. G. Water, nitrogen and weed stress in field corn (Zea mays L.): shoot growth and development. BIOTRONICS 25, 55-65, 1996. Nitrogen (N) balances of soil-crop systems must be monitored more closely in the future to minimize ground water pollution. Maize was grown in rain-sheltered plots on a Flanagan silt-loam soil under three moisture regimes: Wet (W, weekly irrigations equal to water lost by a standard evaporation pan) ; Limited irrigation (L or 1/2 W) and Dryland (D, no irrigation). For each soil moisture regime, supplemental nitrogen (NH4NOg) was applied at 0, 125 and 250 kg N ha-I. Seedlings of common lambsquarter were transplanted 0.15 m apart into the maize rows in sub-plots of each soil moisture regime at the medium N level or 125 kg N ha-I. Soil moisture profiles were measured twice weekly, leaf water potential (1JI1eaf) was monitored with a leaf pressure bomb and root growth was followed at weekly intervals using minirhizotron tubes. Generally yield correlated well with either 1JI1eaf or N per plant. Higher N or water applications led to less negative 1JI1eaf values, one stress substituting for the other in controlling crop stress or yield. Leaf % N as an indicator for yield was compromised by small differences among treatments within sampling dates and the Nx 1JI1eaf interaction; 1JI1eaf as an indictator for when to irrigate was not compromised.