Investigations on Fertigation of Peach on Three Soils I. Migration and Localization of Nitrogen

G. STOILOV, K. KOUMANOV and D. DOCHEV

Institute of Fruit-Growing, BG-4004 Plovdiv, Bulgaria

Abstract

STOILOV, G., K. KOUMANOV and D. DOCHEV, 1999. Investigations on fertigation on three soils. I. Migration and localization of nitrogen. Bulg. J. Agric. Sci., 5: 605-614

The experiment was carried out in lysimeters on three soil types: alluvial-meadow soil (Fluvisol) sandy loam, cinnamon-forest soil (Luvisol) clay loam, and smolnitsa (Vertisol) clay. The fertilizers urea [CO(NH2)2] and phosphoric acid (H3PO4), were supplied through the irrigation system, the annual amounts being partitioned to monthly doses.
It was found that, under favorable temperature conditions in the soil (30-320C), the applied by the irrigation water urea was rapidly hydrolyzed and the obtained ammonium ions were intensively oxidized to nitrates. The easy-movable nitrate nitrogen migrated with the water flows to the periphery of the wetted soil volume where it accumulated in depots of increased nitrate content. The localization of nitrate nitrogen and its concentration in the zones of accumulation proved to be substantially influenced by the root-system's spatial distribution. Two-three weeks after fertigation, the applied nitrogen was completely depleted along the skeletal roots and zones of increased nitrate content were found at the periphery of the areas of intensive root extraction, appearing in the same time inner for the wetted soil volume. The local depletion of the applied nitrogen in the root zone necessitates a greater partitioning of the annual fertilization rate during vegetation in order to provide an optimal nutrition of the plants.

Key words: drip-irrigation, fertigation, urea, lysimeters, peach, root extraction