Nutrient uptake by rice and soil solution composition under atmospheric CO2 enrichment

摘要

Using free-air CO2 enrichment (FACE) we grew rice crops at ambient or elevated (ca. 250 mumol mol(-1) above ambient) and evaluated soil nutrition status by determining the elemental composition of soil solution. The dry matter of rice was increased by elevated CO2. Although the increase in dry matter after panicle initiation was greater in rice grown with FACE than in rice grown in ambient CO2, the increase rate was lower after panicle initiation. The nitrogen (N), phosphorus (P), potassium (K), and magnesium (Mg) concentrations of rice were significantly 21, 6, 14, and 9% lower, respectively, in rice grown with FACE than the concentrations in ambient grown rice at panicle initiation, and the N and K concentrations were significantly lower with FACE at harvest. Although the N and K uptakes of rice were higher with FACE than in ambient grown rice at panicle initiation, the differences were small after panicle initiation. The ammonium, phosphate, K, and silicate concentrations in soil solution gradually decreased before panicle initiation. The relation between the N and K uptake of rice and the concentrations in soil solution indicated the N and K supply from soil regulated the uptake after the concentrations were decreased in soil solution. The N uptake of rice appeared to be determined by the soil N availability, not by nutrition demand and uptake ability of rice after panicle initiation, and the amount of N uptake seemed to limit rice growth.