Purpose: Field studies were carried out in Northern Italy during 2011-2013 to test the possibility to differentiate rates of topdress N fertilisation in rice on a site-specific basis by using reflectance readings, gathered with tractor-mounted sensors. Approach and methods used: The studies were carried out in rice ordinary fields and using conventional farm equipment modified to allow GPS tracking, site-specific fertilisation, and production of rice yield maps. Both NDVI and NDRE indexes were obtained using OptRx sensors. Reflectance measurements were carried out at rice panicle initiation stage. Readings were performed late in the morning on dry vegetation to avoid disturbance from dew drops on vegetation. Site-specific fertilisation rates were set to be inversely proportional to reflectance readings and varied to cultivar, general nutritional status and season. NDVI and NDRE values were related to rice N uptake, estimated by measuring aboveground biomass and N content in sample areas, and to final yield. Key results: Correlation between reflectance indices and rice biomass and N uptake varied among years and cultivars, with a tendency to be higher for NDRE. Site-specific N rates allowed reducing in-field yield variability. Even though the average yield was not significantly increased, this technique allowed a consistent reduction in nitrogen use. Synthesis and Applications: In comparison to the conventional N topdressing application of a uniform rate across the field, site- specific N rates based on reflectance indices allowed to reduce by about 15% the total nitrogen input and to increase NUE (nitrogen use efficiency) by up to 31%.
Site-specific topdress N fertilisation in rice using reflectance indices
VIDOTTO, Francesco;DE PALO, FERNANDO;FERRERO, Aldo
2014-01-01
Abstract
Purpose: Field studies were carried out in Northern Italy during 2011-2013 to test the possibility to differentiate rates of topdress N fertilisation in rice on a site-specific basis by using reflectance readings, gathered with tractor-mounted sensors. Approach and methods used: The studies were carried out in rice ordinary fields and using conventional farm equipment modified to allow GPS tracking, site-specific fertilisation, and production of rice yield maps. Both NDVI and NDRE indexes were obtained using OptRx sensors. Reflectance measurements were carried out at rice panicle initiation stage. Readings were performed late in the morning on dry vegetation to avoid disturbance from dew drops on vegetation. Site-specific fertilisation rates were set to be inversely proportional to reflectance readings and varied to cultivar, general nutritional status and season. NDVI and NDRE values were related to rice N uptake, estimated by measuring aboveground biomass and N content in sample areas, and to final yield. Key results: Correlation between reflectance indices and rice biomass and N uptake varied among years and cultivars, with a tendency to be higher for NDRE. Site-specific N rates allowed reducing in-field yield variability. Even though the average yield was not significantly increased, this technique allowed a consistent reduction in nitrogen use. Synthesis and Applications: In comparison to the conventional N topdressing application of a uniform rate across the field, site- specific N rates based on reflectance indices allowed to reduce by about 15% the total nitrogen input and to increase NUE (nitrogen use efficiency) by up to 31%.
I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
