GROWTH AND YIELD OF MAIZE (Zea mays L.) GROWN OUTDOORS HYDROPONICALLY AND IN SOIL

Maize (Zea mays L.) was grown outdoors hydroponically and in soil to compare yields in the two systems and to determine the extent to which soil temperature and plant nutrition limit yield of soil-grown plants. The hydroponic system consisted of 22.5-L plastic pails filled with "Turface" to which nutrient solution was added at least twice daily. In all 3 yr dry-matter accumulation throughout the growing season was greater on the hydroponic system than in well-fertilized, irrigated sandy-loam soil when planting pattern and density were the same. Maximum aboveground dry matter and grain dry matter on the hydroponic system were 25.8 and 12.2 Mg ha−1, respectively. It is apparent that there is a soil-based constraint that limits aboveground dry-matter production to 75–85% of the potential with the aboveground environment in the region. Grain yield appears to be limited to a lesser extent. To determine the effect of root-medium temperature, growth in pails buried in the soil was compared to that in soil and in pails placed on the soil surface. Although the temperature of the buried pails was consistently lower than that in the aboveground pails and in the soil, dry matter accumulation was similar to that in the aboveground pails indicating that soil temperature was not a cause of the lower yield of the soil-grown plants. There was no evidence that plants growing on the highly fertilized soil were nutrient limited at any growth stage. Other studies have indicated that transient water stress on soil-grown plants will not explain the difference in growth on the two systems. Key words: Maize, hydroponics, soil limitations, soil temperature, nutrition