Water balance and crop coefficient for the 'Folha Murcha' orange in the northwest region of Rio de Janeiro

Brazilian citriculture is carried out in a variety of soils and climates in various regions of the country, with principle development being centred in the Southeast. In the northwestern region of the State of Rio de Janeiro, the conditions of climate and soil are favourable to the cultivation of the orange, with the exception of the volume and distribution of rainfall during the year, which lead to periods of soil water deficit. This study aimed to obtain the components, and carry out the water balance, of a Red-Yellow Argisol in the north-western region of Rio de Janeiro cultivated with the 'Folha Murcha' orange, verifying, for eleven periods over 197 days, the differences arising from the various sites used for monitoring the soil. The crop coefficient (Kc) and the level of response to the water demand of the crop (Ks factor) were also determined. The work was carried out at the Fluminense Federal Institute in Bom Jesus do Itabapoana in the state of Rio de Janeiro, from 13/08/2012 to 26/02/2013. Three plants were monitored for the components of water balance (rainfall, surface runoff, storage, deep drainage and capillary rise). The results showed that the average water consumption of the plants for the whole period was 2.29 mm day^-1, with the greatest demand for water occurring in December, January and February. An average value for Kc of 0.88 was obtained, and it was found that the availability of water in the soil did not fully meet the demands of the plants, ranging from 100% (Ks = 1.0) to only 36% (Ks = 0.36), indicating that in this region, crop performance can be increased by irrigation. As to monitoring the soil, it was concluded that results for the water balance of the 'Folha Murcha' orange can differ depending on the site used for monitoring.

Citrus sinensis L; Osbeck; Soil water storage; Evapotranspiration