Irrigation scheduling of fruit trees according to water balance provided significant differences between locations. In recent years, water status measurements such as water potential have been suggested as irrigation tools in different fruit trees. The aim of this study was to adjust water potential threshold values previously studied and water application approaches that permit the irrigation scheduling of olive trees based on midday stem water potential. The experiments were performed during three seasons (from 2005 to 2007) in two different locations (Badajoz and Ciudad Real) with different weather and cultural conditions. In both locations, the olive orchards were seven years old at the beginning of the experiment but had significantly different canopy development. In Ciudad Real the canopy shaded area at the beginning of the experiment was 15% and the first crop was harvested in 2003. On the other hand, canopy shaded area of the olive orchard in Badajoz experiment was 40% and the first crop was harvested in 2001. Therefore, we assimilated Ciudad Real orchard as young, while Badajoz was mature. Three different irrigation treatments were compared in both locations: Control treatment with traditional water balance as irrigation scheduling and two treatments in which midday stem water potential (SWP) provided the information about water management. In the midday water stem potential irrigation (WI) the threshold value of SWP was -1.2 MPa before the beginning of the massive pit hardening period and -1.4 after this date. Finally, in the deficit treatment (DI) the threshold value of SWP was -2.0 MPa throughout the season. In WI and DI treatment irrigation was applied when SWP reached the threshold value. No significant differences were found between Control and WI in any of the seasons and locations when water potential, leaf conductance, shoot and fruit growth and yield (fruit and oil) were considered. In both locations, the same SWP value in WI treatment produced similar water application as the Control treatment. In DI treatment, shoot growth was significantly reduced in both locations in all the seasons. The SWP in DI trees was clearly affected in both locations, while leaf conductance was only reduced in the Badajoz experiment. In the Ciudad Real experiment no significant differences were found in fruit growth, whereas differences were found in Badajoz. However, yield was significantly reduced in Ciudad Real, but not in Badajoz. WI treatment was successful for no water stress conditions. On the other hand, DI treatment was a mild water stress treatment which reduced yield only in low covert orchard, but not in the ones with almost maximum canopy shaded area. Our work presents an approach for using midday stem water potential in the irrigation scheduling of olive trees. The experiments were performed in two different locations and during three years, in order to establish the usefulness of this approach. The results support that the threshold values suggested for no water stress conditions are the s...

Canopy light interception (LI) is a determining factor for crop growth and yield. Crop yield depends on a canopy's capacity to intercept incident solar radiation, which in turn depends on the available leaf area, its structure, and its efficiency in converting the energy captured by the plant into biomass. Digital images offer a series of advantages over other methods of LI estimation, including the possibility to directly process images by computer for which free software is available. The objectives of this work were to develop a simple, economical method for determining LI in low-lying crops such as processing tomato using digital images obtained with a standard, commercial camera and free software and to evaluate the influence of different types of soil coverage (bare soil and plastic mulch) on LI. Photographs of the selected areas were taken using a digital camera at a distance of 160 cm above the center of each area. The resulting digital images were then analyzed with the free software GIMP 2.2 and IMAGE J. Three methods [area (SA), contour (SC). and reclassification (SR)] were used to quantify the percentage of groundcover (PGC). They were applied to the same images and compared with LI as measured with a line quantum sensor at solar noon. There was a close relationship between LI and estimated PGC with all three methods and for different soil cover regimes. In all cases, there was a linear adjustment with a significant correlation coefficient (P < 0.01) and an r 2 of greater than 0.88. The adjustment with RI was narrowest when the SR method was used to estimate PGC (r 2 = 0.93) followed by SC (r 2 = 0.92) and SA (r 2 = 0.88). Measurements of LI based on digital images offered practical advantages with respect to the use of photosynthetically active radiation bars because the latter must be used at solar noon. In contrast, measurements obtained with a digital camera can be taken at any time of day and bright sunshine is not necessary. Different correlations were obtained for bare soil and plastic mulch conditions, so it was necessary to use a different equation to estimate LI under each condition.

No abstract

No abstract

The growing scarcity and competition for water resources requires the urgent implementation of measures to ensure their rational use. Farmers need affordable irrigation tools that allow them to take advantage of scientific know-how to improve water use efficiency in their common irrigation practices. The aim of this study is to test under field conditions, and adjust where required, an automated irrigation system that allows the establishment of regulated deficit irrigation (RDI) strategies in a stone fruit orchard. For this, an automated device with an algorithm which combines water-balance-based irrigation scheduling with a feedback adjustment mechanism using 15 capacitive sensors for continuous soil moisture measurement was used. The tests were carried out in 2016 and 2017 in Vegas Bajas del Guadiana (Extremadura, Spain) on an experimental plot of ‘Red Beaut’, an early-maturing Japanese plum cultivar. Three irrigation treatments were established: control, RDI and automatic. The control treatment was scheduled to cover crop water needs, a postharvest deficit irrigation (40% crop evapotranspiration (ETc)) strategy was applied in the RDI treatment, while the Automatic treatment simulated the RDI but without human intervention. After two years of testing, the automated system was able to “simulate” the irrigation scheduling programmed by a human expert without the need for human intervention.