Effect of application of inorganic and organic fertilizers on the dynamics of soil nutrients in the rhizosphere

Abstract

The effect of fertilizer application on the dynamics of soil-available nutrients in the rhizosphere was studied in a pot experiment. A rhizobox equipped with a soil solution sampler was used to collect soil solutions and soils in the rhizosphere. The experiment consisted of 6 treatments; soils with application of inorganic fertilizer (NH4NO3, NaH2PO4, KCI), organic fertilizer (rice bran), and without fertilizer application, each of which was either planted or not with maize (Zea mays L.). During the 17-d experiment, soil solutions in the rhizosphere were collected 5 times. After the experiment, soils in the rhizosphereand plants were also sampled. The ionic concentrations of the soil solution and soil extracts with deionized water and the nutrient contents of the plants were then determined. The application of inorganic and organic fertilizers immediately increased the total ionic concentration of the soil solution. As the plant grew, the total ionic concentration of the soil solution in the rhizosphere increased in the inorganic fertilizer treatment mainly due to the accumulation of CI- in the rhizosphere, whereas it decreased in the others. After the experiment, the concentrations of water-soluble N, P, and K decreased i.n the rhizosphere in all the treatments. The decrease in the concentrations of N, P, and K in the treatment without fertilizer extended significantly until 10, 0, and 2 mm from the root surface, respectively. The decrease was generally larger for the fe!tilizer treatments. From these results, the amounts of apparent decrease of N, P, and K in water-soluble forms within or beyond 10 mm from the root surface were calculated, and they were related to the amount of plant uptake. As a result, although the difference among the treatments was not as appreciable as that among elements, the contribution of the net supply of N, P, and K by the replenishment from the soil solid phase was higher for the organic fertilizer treatment than for the inorganic fertilizer treatment.