Ali Motamedi Amin, Hasan Ali Khatinzadeh, Mansour Noori and Daryoush Nikfar
Agricultural Research Department, Karun Agro Industrial, Inc, Shushtar, Iran; alimahohi@yahoo.com
Nitrogen loss in agricultural systems can occur through diverse pathways, one of which involves the leaching of nitrates from waterlogged soil profiles. Nevertheless, there has been a scarcity of investigations concerning the loss of soluble urea in irrigation water, particularly within sugarcane plantations. The objective of this research was to conduct a comprehensive field assessment, followed by a supplementary laboratory investigation, on the phenomenon of urea loss from clay loam soil during the cultivation of sugarcane in the Khuzestan province of southwestern Iran. These objectives were accomplished by monitoring the quantity of irrigation and drained water. A continuous sampling of the drainage water was conducted for 70 days until the third round of urea fertilizer. The daily variations in nitrogen forms were measured by comparison between irrigation rounds, drainage tiles, and drainage time. Data indicate that 11.7%, 4.9%, and 1.99% of the urea fertigation were eliminated via drainage tiles as urea molecules during the first, second, and third rounds, respectively. Which probably related to the preferential flow induced by soil fissures. The concentration of urea losses exhibited a decline in subsequent irrigation rounds, despite higher urea concentrations, indicating a reduction in preferential flow. The highest nitrate loss occurred in the irrigation rounds following urea fertilizer application. Despite similarities in the alterations of urea and nitrate concentrations during irrigation rounds and drainage time, the mechanisms governing these nitrogen forms were found to be distinct. Additionally, the analysis of the soil columns indicated that over 50% of the urea was drained through the soil column (mirroring of the topsoil layer) during both instances of urea fertilizer application, whether it was during the initial or subsequent irrigation.