תפריט נגישות
ניגודיות עדינהניגודיות גבוהה
מונוכרום
הדגשת קישורים
חסימת אנימציה
פונט קריא
סגור
איפוס הגדרות נגישות
להורדת מודול נגישות חינם תפריט נגישותניגודיות עדינהניגודיות גבוההמונוכרוםהדגשת קישוריםחסימת אנימציהפונט קריאסגוראיפוס הגדרות נגישותלהורדת מודול נגישות חינםReducing nitrate leaching from agricultural land to aquifers is a high priority concern for more than a half a century. This study presents theory and observations of a threshold concentration of nitrate in the root zone (Cmax), which the leachate concentration increases at higher rates with increasing root-zone nitrate concentration. Cmax is derived both by direct results from container experiments with varying nitrogen (N) fertigation, and as a calibration parameter in N-transport models beneath commercial agricultural plots. For 5 different crops, Cmax ranged between 20-45 mg/l of NO3 -N derived from experiments and models. However, for lettuce, which was irrigated with a large leaching fraction, Cmax could not be defined. In crops irrigated and fertilized in the warm/dry season (corn and citrus), the experiments show a dramatic change in leachate-concentration slope, and simulations reveal a wide range of sensitivity of leachate NO3 -N concentration to Cmax. In annual crops irrigated and fertilized in the cool/wet season (e.g., potato in a Mediterranean climate), the experiments show a distinct Cmax that is less dramatic than that of the summer-irrigated crops in the container experiment, and smaller impact of Cmax in N-transport models. The simulations show that, for summer-irrigated crops, maintaining fertigation at C < Cmax has a significant effect reducing deep leachate concentrations, whereas for the winter annual crops the simulations revealed no threshold effect. It is suggested that for summer-irrigated crops, fertigation below Cmax robustly serves the co-sustainability of intensive agriculture and aquifer water quality; this is also suggested for winter crops, but benefits are not robust. For short season, small root-system crops (e.g., lettuce), efforts should be made to detach the crop from the soil.
Reducing nitrate leaching from agricultural land to aquifers is a high priority concern for more than a half a century. This study presents theory and observations of a threshold concentration of nitrate in the root zone (Cmax), which the leachate concentration increases at higher rates with increasing root-zone nitrate concentration. Cmax is derived both by direct results from container experiments with varying nitrogen (N) fertigation, and as a calibration parameter in N-transport models beneath commercial agricultural plots. For 5 different crops, Cmax ranged between 20-45 mg/l of NO3 -N derived from experiments and models. However, for lettuce, which was irrigated with a large leaching fraction, Cmax could not be defined. In crops irrigated and fertilized in the warm/dry season (corn and citrus), the experiments show a dramatic change in leachate-concentration slope, and simulations reveal a wide range of sensitivity of leachate NO3 -N concentration to Cmax. In annual crops irrigated and fertilized in the cool/wet season (e.g., potato in a Mediterranean climate), the experiments show a distinct Cmax that is less dramatic than that of the summer-irrigated crops in the container experiment, and smaller impact of Cmax in N-transport models. The simulations show that, for summer-irrigated crops, maintaining fertigation at C < Cmax has a significant effect reducing deep leachate concentrations, whereas for the winter annual crops the simulations revealed no threshold effect. It is suggested that for summer-irrigated crops, fertigation below Cmax robustly serves the co-sustainability of intensive agriculture and aquifer water quality; this is also suggested for winter crops, but benefits are not robust. For short season, small root-system crops (e.g., lettuce), efforts should be made to detach the crop from the soil.
