Localized phosphorus application via P-dipping is more effective for improving initial rice growth in lower temperature conditions

ABSTRACT P-dipping is a practical approach for smallholder farmers to increase lowland rice yields with minimal fertilizer inputs by coating seedling roots with P-enriched slurry at transplanting. The effect of such localized application increases by concentrating more nutrients near the roots; however, this also increases the risk of salt stress known as fertilizer burning. The study aimed to identify the effect and burning risk of P-dipping on the initial rice growth under a range of temperatures. Rice seedlings were dipped instantly or for 2 h in slurry with different P2O5 concentrations at 0% (P0), 2.3% (P1), and 4.4% (P2), transplanted with the slurry attached to the seedling roots, and grown for 21–28 days at the day/night temperatures of 28°/20°C, 33°/25°C, and 36°/27°C. A significant interaction effect was detected between the P2O5 concentrations and growing temperatures on shoot biomass. With the P-dipping treatments, shoot biomass was increased 4.8–5.2 times at 28°/20°C. The effect of P-dipping became less significant with increasing temperatures because of the greater rates of withered leaves soon after transplanting. Burning damage was the greatest when the P2 treatment was combined with longer dipping duration at the 36°/27°C, nullifying the effect of P-dipping on shoot biomass. The results clearly showed that localized P application is more effective under lower temperatures, with lower risk of fertilizer burning. Elevated temperatures may disturb the effort to increase rice yields with minimal fertilizer inputs via localized application. GRAPHICAL ABSTRACT