Cyclic Sprinkler Irrigation and Pre-irrigation Substrate Water Content Affect Water and N Leaching from Containers

Abstract

Abstract A series of sprinkler irrigation experiments were conducted to determine the influences of water application rate (WAR), pre-irrigation substrate water content (PSWC), and cyclic irrigation on water and N leaching from container-grown plants. Prior to experiments, Marigold (Tagetes erecta L. ‘Apollo’), were glass house-grown in pine bark-filled 3.8 liter (1 gal) containers. Prior to treatment, substrate was dried via evapotranspiration (ET) to targeted PSWCs. A simulated overhead irrigation system applied the daily water allotment in a single continuous application or cyclically (multiple applications); in most cases the respective ET volumes were applied to the substrate. Water application efficiency (WAE; water vol retained in substrate + water vol applied to substrate) was determined, and in some experiments, leachates were analyzed for EC, NO3-N and NH4-N. A negative linear relationship existed between WAR and WAE. Leachate NO3-N and NH4-N concentrations were unaffected by WAR, however, total N leached increased with increasing WAR. WAE of cyclic irrigation was 4% higher (absolute basis) than with continuous irrigation; WAE increased as the time interval between cyclic applications increased from 20 to 60 min. Regardless of how water was applied, WAE was inversely related to PSWC and application volume. These experiments showed that the most effective method to increase WAE is to irrigate at relatively low PSWCs; if irrigation occurs at relatively high PSWCs, then relatively low volumes should be applied.