園芸ジャーナル
オープンアクセス

概要

Influence of Nitrogen Limitation and Long-Term Use of Rockwool on Nitrous Oxide Emissions in Hydroponic Systems

Shin-nosuke Hashida, Kazuyoshi Kitazaki, Kazuhiro Shoji, Fumiyuki Goto and Toshihiro Yoshihara

To mitigate Nitrous Oxide (N₂O) emissions derived from Nitrogen (N) fertilizer of agroecosystems, establishment of best management protocols for cultivation is necessary. Hydroponic systems using rockwool have the potential to reduce N₂O emissions; however, the effects of nutrient condition and retained N compounds in rockwool on N₂O emissions remain unclear. The primary objective of our study was to understand the crucial factors behind emissions of N₂O. Tomato cultivation with low levels of nutrient showed reduced growth and yield, but increased N₂O emission. In contrast, growth and N₂O emissions were increased by cultivation with normal levels of nutrient and used (1-y-old) rockwool containing excess N compounds from the previous year's cultivation. Though the long-term use of rockwool significantly enhanced seasonal N₂O emission, the availability of N₂O precursors NO₃^- and NH₄⁺ did not clearly explain the variation in N₂O fluxes during cultivation. Rather, environmental factors, such as relative water content of rockwool in the rhizosphere, were significantly correlated to N₂O emissions during cultivation under various conditions. We conclude that environmental factors most strongly influence the fate of available environmental substrates remaining in rockwool, and thereby control N₂O emissions.