Nitrogen application in dry-seeded delayed-flooded rice in Italy

Abstract

Dry-seeded delayed-flooded rice in Italy is important in some areas with high sand content. The effects of N application timing and rates on grain yield, milling yield, plant height, total biomass, harvest index (HI) and crop N content were evaluated for dry-seeded delayed-flooded rice in Italy to increase the N use efficiency and to study N fertilizer recommendations. Two widely grown non-semi-dwarf varieties were studied: Drago and Loto. Three N rates were used: 60, 120 and 180 kg N ha−1. For each rate the fertilizer was applied in seven splits across three growth stages: pre-sowing, pre-flooding and panicle differentiation. Drago produced higher yields and N application at all stages increased yield. Late N application caused the development of secondary sterile tillers, decreasing harvest index. Loto responded to earlier N applications but not to late N applications. In contrast with other trials outside Italy, pre-plant N fertilization was effective in increasing yield. Brown rice and total milled rice yields were higher for Loto. Increasing the applied N rate increased the head rice yield range. With low N no low values were recorded and variation between splits was small. With high N the highest head yield was observed with split application. Height was significantly affected by N rate and split, with a range of 65 to 92 cm and 54 to 86 cm for Drago and Loto, respectively. N application at tillering was more effective. N rate and split affected biomass and decreased HI. Crop N content at maturity was affected by late N application and by total applied fertilizer. N content in the panicle showed lower variation with N split and rate and was negatively correlated with yield. At 120 and 180 kg N ha−1 all nitrogen applied pre-flooding gave good results in both sites, but the best results were obtained with N split at pre-sowing and pre-flooding, with low yield increase moving from 120 to 180 kg N ha−1. We recommend late N applications for Drago (medium-late variety), but not for Loto (early variety).