| Summary: | Nitrate (NO3-) leaching from fertilized land can be detrimental to aquatic ecosystems and human health. Although NO 3- leaching potential is generally found to be low in turfgrass, certain conditions can occur that result in increased leaching loss of nitrogen. Kentucky bluegrass (Poa pratensis L.) is the most widely used cool-season turfgrass species in the temperate and subarctic climate zones in the United States. Due to its popularity, many new cultivars are bred and released each year. Despite the ample amount of information characterizing the agronomic features of Kentucky bluegrass genotypes, little is available documenting their physiological characteristics related to nitrogen use efficiency and how these might affect the NO3 - leaching potential of the genotypes. Such information would be of great value for both scientists and customers. In this comprehensive study, a screening procedure was developed using nutrient solution culture to evaluate differences in NO3 - uptake among sixty Kentucky bluegrass genotypes. Two cultivars were selected from the sixty to represent genotypes having high vs. low capacity for NO3- uptake. These two cultivars were then used to examine the relationship between NO3- uptake efficiency and competitiveness for soil nitrogen. Finally, these two cultivars were compared to determine if NO3- uptake efficiency affected NO3- leaching potential. There were significant differences in NO3- uptake at both high (1 mM) and low (0.05 mM) N concentrations among sixty Kentucky bluegrass genotypes, with a strong correlation between uptake rates at high and low N concentrations. Julia and Midnight were selected as representing cultivars with efficient and inefficient nitrate uptake, respectively. In nutrient solution culture, Julia exhibited 56% higher NO3 - uptake rates than Midnight. In a root competition study, in which the root systems of the two cultivars occupied the same soil volume, Julia was more competitive for nitrogen acquisition (absorbed 20 to 71% more NO 3- ) than Midnight. However, the higher NO3 - uptake capacity and better competitiveness for soil N in Julia did not result in lower NO3- leaching potential. These results suggest that differences in root morphology and architecture may play a more important role than uptake capacity in determining nitrate leaching potential among Kentucky bluegrass genotypes.
|
|---|