DRY MATTER ACCUMULATION OF MAIZE GROWN HYDROPONICALLY UNDER CONTROLLED-ENVIRONMENT AND FIELD CONDITIONS

Abstract

The early-maturing maize (Zea mays L.) hybrid Pioneer 3978 was grown hydroponically in controlled-environment growth rooms during a 4-yr period. Plant dry matter accumulation and distribution were measured from 15 days before silking until date of black layer formation. Light distribution in the maize canopy and leaf carbon exchange rates at various positions in the canopy were measured and leaf area index and leaf area distribution were calculated, in order to compare crop growth rates with estimated rates of crop dry matter accumulation. In addition, Pioneer 3978 and two late-maturing maize hybrids, DeKalb XL55 and DeKalb XL72AA were grown in the field using the same hydroponic system employed in the growth rooms. Dry matter accumulation, dry matter distribution and grain yield were measured for the field-grown maize. Average crop growth rate for maize grown in the growth rooms from 15 days before to 15 days after silking was in excess of 40 g∙m−2∙day−1, with an efficiency of conversion of photosynthetic-active radiant energy into plant dry matter of 12.9%. Rate of dry matter accumulation declined to approximately 20 g∙m−2∙day−1 during the period from 15 days after silking to date of black layer formation. Average final dry matter and grain yield for the 4-yr experiment were 26.0 and 11.5 tonnes/ha, respectively. Estimated rates of dry matter accumulation by the maize canopy as calculated from photosynthesis-irradiance response curves, leaf area and measurements of light distribution appeared to indicate a substantial increase in nonfoliar respiration during the period of rapid dry matter accumulation of the grain. The hydroponic system, consisting of "Turface" — supporting medium and nutrient solution, did appear to enhance rate of dry matter accumulation. Maximum crop growth rates of hydroponically grown maize in the field were 52–2 g∙m−2∙day−1, which is more than 50% higher than maximum crop growth rates of field-grown maize at Guelph. Results of these experiments indicate that the inherent yield potential of maize is much higher than yields obtained under normal field conditions.Key words: Zea mays L., crop growth rate, dry matter distribution, photosynthetic efficiency, yield potential, carbon exchange rate