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Effect of soil available water depletion on plant water status, fruit size and yield of avocado trees cv. 'HASS'

Ferreyra, R., Selles, G., Gil, P., Celedon, J., Maldonado, P.
Acta horticulturae 2014 no.1038 pp. 393-399
adults, aeration, air, avocados, crop yield, environmental factors, evapotranspiration, humidity, irrigation scheduling, orchards, oxygen, plant available water, soil types, soil water content, stomatal conductance, stomatal movement, texture, trees, water potential
The objective of this study was to define the soil available water depletion (SAWD) in avocado, in order to use it as a criterion for irrigation programs in soils of fine texture and low aeration capacity. to determine appropriately the fraction of soil SAWD we performed three independent trials: Trial 1: We evaluated two treatments: T1, irrigation to 100% ETc and then without irrigation for 13 days, until the SAWD reached 60%, and T2: daily irrigation replacing 100% of the evapotranspiration of the crop (ETc). Trial 2: We evaluated three fractions of SAWD before irrigating again: T1: 5%; T2: 30% and T3: 60%. Trial 3: We monitored the SAWD variation in seven orchards of adult avocados. SAWD was monitored using a capacitive probe to determine which percentages of SAWD changed the velocity of water extraction by the trees. Decreases of SAWD up to 60% before irrigating did not affect the plant water status measured as midday stem water potential (MSWP). Also, stomatal conductance (gs) and yield was not affected. According to our results, avocado transpiration is maintained with low soil humidity. This may indicate that avocado has less stomatal regulation compared to other species. It could be related to the environmental conditions in which these species evolved. This characteristic of avocados, which may sometimes be a limiting factor, may provide an advantage in irrigation management in soils with low air capacity, since it will allow decreasing soil water content without producing stomatal closure, thus improving the oxygen flow in this type of soil.