A SOLUTION-CULTURE ASSESSMENT OF PHOSPHORUS STATUS ON MAIZE GROWTH AND NUTRIENT DYNAMICS

 Phosphorus (P) is a key element for maize (Zea mays L.) production and plays many important roles in plants. Soil-buffering of P does not allow for precise control of solution concentrations in the field, while greenhouses, growth chambers, and hydroponics provide limiting conditions. Thus, an objective of this study was to develop a practical technique for cultivating several maize plants to physiological maturity (R6) in a growth room environment, with precise control of nutrient availability and timing, and evaluate its utility for the purpose of measuring plant responses to variations in P concentration using a silica-sand-based solution culture technique. A semi-automated growth room for conducting nutrient studies on 96 maize plants was constructed and evaluated to quantify plant growth response to a range of solution P concentrations. Maize yield components were measured and compared to values for field-grown plants. Due to ideal conditions and successful simulation of light intensity, diurnal fluctuations in temperature and relative humidity, and changing photoperiod, grain yield and tissue nutrient concentrations were comparable to field-grown maize, although with greater shoot biomass. The second objective was to quantify the uptake and partitioning of nutrients as affected by P concentration at various maize growth stages. Thus, two maize hybrids were grown under both sufficient and insufficient P fertility rates using the silica-sand-based solution culture technique. Throughout the growth stages, sufficient-P plants had more than double the biomass compared to insufficient-P plants. At R1, N partitioning followed a similar pattern in both treatments, while P remobilization differed, with insufficient-P plants relying on stem tissue and sufficient-P plants remobilizing P from leaf and root tissue for grain production. Plants grown under sufficient-P fertility matured more rapidly and reached physiological maturity (R6) sooner. Sufficient-P fertility resulted in 2- to 3-fold greater grain, leaf, stem, and root biomass at R6 than insufficient-P. Nutrient partitioning patterns to plant tissues between P treatments were generally similar, except for insufficient-P plants allocating more nutrients to root tissues than sufficient-P plants. Partitioning patterns for B and Cu indicated that the high demand of maize reproductive structures for these nutrients may justify a foliar application of B and/or Cu at vegetative growth stages in some cases. The results of these studies suggests that there is great utility in further utilizing this silica-sand-based solution culture technique for more complex plant nutrient studies.