Note 73 — Chapter III · THE POSITION OF NITROGEN IN AGRICULTURE.
Reading edition
"Under prolonged kitchen-garden culture the subsoil becomes enriched with nitrogenous matter to a far more considerable depth; this has been shown by the analyses of the soil of the old kitchen-garden at Rothamsted. This is doubtless due to the practice of deep trenching employed by gardeners."—R. Warington, 'Lectures on Rothamsted Experiments.' U.S.A. Bulletin, p. 24.