|Nunes De Lima, Roberta - Universidade Estadual Do Norte Fluminense|
|Figueiredo, Fabio - Universidade Estadual Do Norte Fluminense|
|Martins, Amanda - Universidade Estadual Do Norte Fluminense|
|De Deus, Bruna - Universidade Estadual Do Norte Fluminense|
|Ferraz, Tiago - Universidade Estadual Do Norte Fluminense|
|Gomes, Mara - Universidade Estadual Do Norte Fluminense|
|De Sousa, Elias - Universidade Estadual Do Norte Fluminense|
|Campostrini, Eliemar - Universidade Estadual Do Norte Fluminense|
Submitted to: Scientia Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/2014
Publication Date: 12/24/2014
Citation: Nunes De Lima, R., Figueiredo, F., Martins, A., De Deus, B., Ferraz, T., Gomes, M., De Sousa, E., Glenn, D.M., Campostrini, E. 2014. Partial rootzone drying (PRD) and regulated deficit irrigation (RDI) effects on stomal conductance, growth, photosynthetic capacity, and water-use efficiency of papaya. Scientia Horticulturae. DOI: 10.1016/j.scienta.2014.12.005.
Interpretive Summary: New irrigation strategies are needed to meet the future demand for water in tropical papaya production. Two irrigation strategies (partial rootzone drying [(PRD) and regulated deficit irrigation (RDI))] were imposed in greenhouse and field studies and compared with full irrigation (FI) and no irrigation (NI). PRD and RDI both reduced growth, photosynthesis and water use at a 50 percent water defict but had no negative effect at a 30 percent water deficit. We established a threshold for irrigation that can be used to reduce irrigation in the field without reducing yield or fruit quality.
Technical Abstract: Papaya (Carica papaya, L.) is an important economic crop in tropical and subtropical countries in addition to its human health benefits. Papaya is a giant herbaceous species and maintaining adequate tissue turgidity and water availability is necessary to maintain the rigidity of the stem as well as increase productivity. Alternative irrigation techniques will be needed in the future due to the possibility of water shortages related to climate change. The morphological and physiological responses of ‘Grand Golden’ papaya to partial root drying (PRD), regulated deficit irrigation (RDI), and no irrigation followed by re-hydration (NI) was compared with full irrigation (FI), with plants grown in pots with roots split equally between two soil columns and in a field study. In FI, the whole root system was irrigated at 100 percent of water use; in RDI, 50 percent or 70 percent of FI water use was supplied to the whole root system (greenhouse and field study, respectively); in PRD, 50 percent, 70 percent or 100 percent of FI was supplied to one soil column while the other was allowed to dry (greenhouse, field and field study, respectively). NI received no irrigation after the start of the study and only rainfall in the field study. The application of 50 percent water use in PRD and RDI decreased the shoot and root dry mass production, with a more pronounced effect on root dry weight. This decrease in biomass was associated with a decrease in net photosynthetic rate. In the field study, a 30 percent water deficit in PRD and RDI treatments did not significantly reduce vegetative growth or yield components, compared to FI. There was evidence of a non-hydraulic signal in the PRD treatments compared to RDI decreasing Gs but it was insufficient to affect shoot growth or yield components. There was no difference in the instantaneous WUE of PRD or RDI treatments in the greenhouse or the agronomic WUE in the PRD and RDI treatments in the field, but both treatments improved water use efficiency compared to FI. A 50 percent water deficit in the greenhouse study for the PRD and RDI treatments was sufficient to significantly reduce biomass and dry matter partitioning compared to the FI treatment. In the field study, a 30 percent water deficit in both PRD and RDI treatments did not significantly reduce vegetative growth or yield components, compared to FI. It appears that papaya can tolerate moderate water deficits without a significant reduction in yield components indicating that less than 100 percent ET0 irrigation replacement can be scheduled, but there is little or no benefit to PRD to justify the additional irrigation and management expenses.