Characterization of ambient conditions inside greenhouses of papaya (Carica papaya L.) crops in the Canary Islands

Quality problems observed at certain times of year, related to low soluble solids content (degrees Brix), have restricted the exportation market and, thus, the expansion of papaya cultivation in the Canary Islands. In order to develop new management strategies oriented to maintain a steady marketable fruit supply all year around, it is necessary to improve our knowledge of crop phenology under the specific climatic conditions of the islands. The present study was conducted during a 2-year commercial crop cycle, from April 2015 to March 2017. Two commercial papaya fields under plastic-cover greenhouses were selected; one on the south (SP) and the other on the north (NP) shore of Tenerife. Meteorological variables [air temperature, relative humidity and photosynthetically active radiation (PAR)] were logged inside the selected greenhouses. Production and total soluble solids (TSS) content of the fruit, as a commercial quality parameter, were measured weekly. In winter, the daily average of growing degree days (GDD) and cumulative PAR were significantly higher in SP. However, in spring, GDD was higher in NP, while, in summer and winter, no significant differences were found between orchards. As a consequence of such differences in meteorological conditions, the papaya production periods were different at each greenhouse: from October to March in SP and from February to August in NP. Moreover, fruits from the SP greenhouse presented higher TSS (above 12 degrees Brix all year round) than in the NP, where TSS dropped off to below 12 degrees Brix from January to June. Scheduled cultivation on both shores of the island could improve the availability of papaya to supply the market throughout the year. Although the study suggests that the SP greenhouse produced fruit with better quality, further research is necessary in papaya crop management to increase fruit quality in the NP area, especially for fruit that is going to be harvested from January to June.