AUTHOR=Avellaneda Bohórquez César Augusto , Martinez Herminia Emilia Prieto , Santos Ricardo Henrique Silva TITLE=Kinetic Parameters of Nitrate Absorption by Adult Coffee Trees JOURNAL=Frontiers in Sustainable Food Systems VOLUME=5 YEAR=2021 URL=https://www.frontiersin.org/journals/sustainable-food-systems/articles/10.3389/fsufs.2021.677580 DOI=10.3389/fsufs.2021.677580 ISSN=2571-581X ABSTRACT=

Nitrogen, the most demanded nutrient by coffee plants, has a rate of recovery from the soil of about 50%. Because of that high doses of nitrogenous fertilizers are used to reach high production, and consequently high amounts of N are lost to the environment. Knowing the kinetic parameters of nitrate (NO₃^-) absorption over the fruit development cycle is important as a mean of achieve more adjusted fertilizer doses and better recovery rates for the N applied as fertilizers. This study aimed determining the kinetic parameters of NO₃^- absorption in different development stages of fruits from adult coffee plants. The kinetic parameters V_max and K_m were determined in a low production year, at the pinhead (PH), rapid expansion (RE), grain filling (GF), and maturation (MT) stages. One month before each kinetics assay, lateral roots of eight plants were excavated and wrapped into non-woven fabrics grow cylinders filled in with vermiculite to produce absorbent roots. On the assay day, the roots were washed and immersed into a container with 1 L of 90 μmol L⁻¹ NO₃^- solution. Sampling began one and a half hours after that, and was taken every hour over 7 h. Data on NO₃^- depletion were used to calculate the absorption kinetic parameters V_max and K_m. In a low production year the V_max ranged from 0.14 to 0.72 μmol g⁻¹ h⁻¹ in a root fresh matter basis and K_m from 6.47 to 50.31 μmol L⁻¹. The V_max values were highest at the PH and MT stages; the lowest absorption rate was recorded at GF and K_m was lowest at RE. As at the RE stage of fruits V_max shows a positive correlation with grain production, adequate nitrogen availability must be ensured before this phase to not to affect coming coffee production.