Abstract
The “drip irrigation and liquid fertigation system with year-round plastic mulching (MD system)” is a cultivation method whereby plants are irrigated using a drip tube underneath a plastic mulch sheet. This study investigated how an MD system affected nitrogen (N) leaching by measuring the changes in soil inorganic N levels in a satsuma mandarin orchard.
In the control plot, N, in the form of solid fertilizer, was applied to the surface of the soil according to local fertilization practice. In the MD plot, N, in the form of liquid fertilizer, was applied using the MD system. The amount of N in the MD plot was 60% of the control plot. The total amount of inorganic N in the soil, which was collected at 30–60 cm apart from the tree trunk, was measured in consideration of the distance from the drip tube. As a result, the total amount of inorganic N after cultivation in the MD plot was lower than that in the control plot. The amount of leached N was estimated from the levels of soil inorganic N before and after cultivation, amount of fertilizer N added, and plant absorbed N in the fruit. The estimated amount of leached N from the MD plot was less than that from the control plot. The N applied through irrigation water, which contained nitrate, was similar to the estimated amount of N that leached from the MD plot. Therefore, the results suggest no net N leaching from the MD plot.
In conclusion, the MD system effectively reduced N leaching in the citrus orchard.
