2013 journal article
Nitrate Uptake Rates of Kentucky Bluegrass Genotypes and Their Effect on Nitrate Absorption under Competitive Conditions
CROP SCIENCE, 53(3), 1179–1188.
ABSTRACT Nitrate leaching from turfgrasses continues to be a concern. It is proposed that selecting turfgrass genotypes with higher NO 3 − absorption abilities could reduce NO 3 − leaching. This study examined the intraspecific difference in NO 3 − absorption among Kentucky bluegrass ( Poa pratensis L.) genotypes and how such a difference affects N absorption when roots are in competition for soil N. A nutrient solution screening procedure was used to identify Kentucky bluegrass genotypes having high vs. low NO 3 − uptake capacity. Tillers of 60 Kentucky bluegrass cultivars were rooted and transferred to a continuous flow solution culture system. After establishment, plants were treated to develop moderate N deficiency. Isotopically labeled ( 15 N) KNO 3 was introduced at high (1 mM) and low (0.05 mM) concentrations to screen for differences in NO 3 − uptake. After a brief uptake period, plants were harvested, dried, and analyzed for 15 N content to determine N uptake rate. There were significant differences among genotypes for uptake rate at both high and low N concentrations. The 60 genotypes exhibited a wide range of uptake rates, with strong correlation between rates at high and low N. The cultivars Julia and Midnight were selected as representing cultivars with efficient and inefficient NO 3 − uptake, respectively. Julia had NO 3 − uptake rates averaging 56% higher than Midnight. A subsequent lysimeter study examined whether higher NO 3 − uptake capacity would translate into increased N absorption under competitive conditions. Tillers of the two cultivars were planted as a mixed stand in soil or sand column lysimeters. After establishment, 15 N‐labeled KNO 3 solution at high (2 or 1mM) and low (0.05mM) concentrations was applied to each column. After an uptake period, individual plants of each cultivar were harvested for 15 N analysis. Results indicated that Julia absorbed 20 to 50% more NO 3 − than Midnight at the high N concentration and 25 to 71% more NO 3 − more than Midnight at the low N concentration. Most differences were statistically significant. This indicates that differences in NO 3 − absorption by Kentucky bluegrass identified in solution culture translate into differences in absorption of soil N.