Deficit irrigation effect on fruit yield, quality and water use efficiency: A long-term study on Pêra-IAC sweet orange

Brazil stands out in world citrus production, as it is responsible for the largest cultivated area and production amounts. In the last decade, Sao Paulo State fruit yield improved due to adoption of technologies such as irrigation and fertilization. Considering the need for improving yield, quality and water resources sustainable use in agriculture, the aim of this study was to evaluate the effect of deficit irrigation on Pêra-IAC orange fruit yield, juice quality and water use efficiency. The experiment was carried out in a Pera sweet orange grafted onto Sunki mandarin orchard. Water was applied by drip irrigation system and there were five treatments testing different irrigation depths: T100 - 100 % of crop evapotranspiration (ETc), T75 - 75 % ETc, T50 - 50 % ETc, T25 - 25 % ETc and T0 - rainfed. Six replications per treatment were randomized in blocks for statistical analysis. Fruit yield was evaluated by weighing all fruits per tree and quality characteristics were monitored by samplings during maturation period until harvest. Five harvesting years were evaluated, from 2013/14–2017/18. Results were tested by analysis of variance, Tukey's means test and Scott-Knott grouping test (α = 0,05). Irrigation improved fruit yield in three out of five seasons, even when applying only 25 % of ETc. Irrigation yield increments ranged from 15 to 64 % when compared to rainfed treatment. Deficit irrigation improved fruit quality compared to the full-irrigated trees (T100), as it resulted in lower acidity and higher maturation index. After five seasons, fruit yield in irrigated treatments was increased by 30.8 % compared to the rainfed. Water use efficiency showed that deficit irrigation applying 50 % ETc is an interesting strategy for increasing yield, quality and saving water.