Morphological, physiological and kinetic parameters related to nitrogen uptake efficiency in hop cultivars (Humulus lupulus L.)

Hops are cultivated in fertile soils in temperate climates. However, have been cultivated in countries in subtropical and tropical regions, where the soils have low availability of nitrogen (N) to plants. Therefore, N fertilization is necessary. However, hop cultivars may have different kinetic parameters of absorption, which may provide greater or lesser efficiency in the absorption of N forms. The study aimed to evaluate the kinetic parameters related to the absorption of mineral N forms in hop cultivars. Cultivars ‘Cascade’, ‘Chinook’, and ‘Columbus’ after 21 days of cultivation in a 50% Hoagland solution were transferred to a CaSO4 solution (0.01 mol L−1) for 10 days, in order to deplete their internal reserves. Photosynthetic and morphological variables, total N concentration in cultivar organs, and NO3- and NH4+ concentrations in the solution was analyzed. Cultivar ‘Columbus’ showed higher fresh matter production potential, good photosynthetic performance, higher maximum absorption rate values for NO3- and NH4+, and higher NO3- influx values, indicating that it is suitable for cultivation in substrates with high N availability. Cultivar ‘Chinook’ had the greatest photosynthetic potential and, therefore, it can show rapid growth and high productivity and lower concentration minimum value, indicating that it can perform well in environments with low N availability. ‘Cascade’ showed higher root growth potential, higher tissue N concentration values in different parts, and higher NH4+ influx values, indicating that it is suitable for soils with high NH4+ availability. Kinetic parameters can be used to select genotypes that are more efficient in nutrient uptake. Hop cultivation is possible in southern Brazil. Different hop cultivars in different effects at photosynthetic and kinetic parameters. The amount and form of N available in the soil can increase the efficiency of certain hop varieties. It is possible to produce more sustainably and save resources with the knowledge of the kinetic parameters of hop cultivars.