Early evaluation of popcorn hybrids for vegetative use efficiency of nitrogen and phosphorus and secondary traits.

The vegetative use efficiency of nutrients by popcorn genotypes is poorly characterized. Thus, the objectives of the present study were to (i) evaluate the vegetative use efficiency of nitrogen (N) and phosphorus (P) and second ary traits in commercial popcorn hybrids, and (ii) investigate the relative importance of root traits for the vegetative use efficiency of these nutrients in popcorn. Five popcorn hybrids were assessed in the vegetative stage V6 (six fully expanded leaves) in two distinct experiments with contrasting N and P levels at greenhouse. The hybrids were evaluated regarding the vegetative use efficiency (VUE) of N or P and the following secondary traits: daily growth (DG), shoot (SDW) and root dry weight (RDW), root-to-shoot ratio (RSR), total length (TRL), surface area (RSA), and root volume (RV). Significant differences between the hybrids were observed for all traits in both experiments. The hybrid x nutrient interaction was also significant for UE in both experiments, and the hybrids had different UEs under each nutrient level individually. The values for shoot traits decreased from high to low N, while values for root traits increased from high to low P. Hybrids P802 and AP4502 were notable due to their high vegetative N use efficiency under high and low N, respectively, and hybrids P622 and AP2501 were the most efficient in P use under high and low P, respectively. Regardless of the experiment and the nutrient level, hybrid P625 was consistently regarded as inefficient in vegetative nutrient use. The hybrids that were efficient in vegetative nutrient use had greater root trait values than the inefficient hybrids, regardless of the experiment, the nutrient level and the root class.