Northern, Israel
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Levin A.G.,Northern RandD | Naor A.,Northern RandD | Noy M.,Israeli Extensions Office | Love C.,Israeli Extensions Office | And 2 more authors.
Acta Horticulturae | Year: 2015

Throughout Israel, drought and scarce fresh water resources endanger the sustainability of irrigated agriculture. Scientific knowledge regarding water deficit irrigation at different phenological periods in mango trees, and the consequences for fruit quantity and quality, is very limited. The effect of four irrigation levels (100 [control], 125, 75 and 50%) at three different phenological periods (1 - fruit set to pit hardening; 2 - pit hardening to harvesting; 3 - postharvest) was tested on 'Keitt' in the Jordan Valley in Israel. Although this research was initiated in June 2010, the 2011 production year was chosen as a representative year for this paper. In the first phenological period, irrigation level did not affect the number of fruit or average fruit size per tree, however number of fruits per tree tended to increase with increasing irrigation. This trend was not observed for fruit size (weight), however average fruit size and the fruit size distribution tended to decrease with increasing irrigation. In the second phenological period, the number of fruit increased slightly (non-significant) with increasing irrigation, but in contrast to the first phenological period, average fruit size and fruit size distribution also increased at higher irrigation levels. In the postharvest irrigation treatments (2011), average fruit size was significantly higher by 30% at 125% irrigation compared to 50% irrigation, however the 8% increase in number of fruits was not significant. Similarly, irrigation treatments did not affect number of new flushes or flush length. Inflorescence length (as a proxy for inflorescence age) and number were significantly greater in the two deficit irrigation treatments compared to 125% irrigation. These results reflect an earlier onset of flowering in the deficit irrigation treatments compared to the well-irrigated ones. Our results show that the postharvest phenological period is the most sensitive to water stress and has the largest impact on both quantity, and in particular, quality (fruit weight) of fruit production under Israeli growing conditions (sub-tropical).

Assouline S.,Institute of Soil, Water and Environmental Sciences | Russo D.,Institute of Soil, Water and Environmental Sciences | Silber A.,Northern RandD | Or D.,ETH Zurich
Water Resources Research | Year: 2015

The challenge of meeting the projected doubling of global demand for food by 2050 is monumental. It is further exacerbated by the limited prospects for land expansion and rapidly dwindling water resources. A promising strategy for increasing crop yields per unit land requires the expansion of irrigated agriculture and the harnessing of water sources previously considered "marginal" (saline, treated effluent, and desalinated water). Such an expansion, however, must carefully consider potential long-term risks on soil hydroecological functioning. The study provides critical analyses of use of marginal water and management approaches to map out potential risks. Long-term application of treated effluent (TE) for irrigation has shown adverse impacts on soil transport properties, and introduces certain health risks due to the persistent exposure of soil biota to anthropogenic compounds (e.g., promoting antibiotic resistance). The availability of desalinated water (DS) for irrigation expands management options and improves yields while reducing irrigation amounts and salt loading into the soil. Quantitative models are used to delineate trends associated with long-term use of TE and DS considering agricultural, hydrological, and environmental aspects. The primary challenges to the sustainability of agroecosystems lies with the hazards of saline and sodic conditions, and the unintended consequences on soil hydroecological functioning. Multidisciplinary approaches that combine new scientific knowhow with legislative, economic, and societal tools are required to ensure safe and sustainable use of water resources of different qualities. The new scientific knowhow should provide quantitative models for integrating key biophysical processes with ecological interactions at appropriate spatial and temporal scales. © 2015. American Geophysical Union. All Rights Reserved.

Sperling O.,Ben - Gurion University of the Negev | Shapira O.,Northern RandD | Shapira O.,Hebrew University of Jerusalem | Tripler E.,The Southern Arava RandD | And 2 more authors.
Irrigation Science | Year: 2014

Irrigation of crops in arid regions with marginal water is expanding. Due to economic and environmental issues arising from use of low-quality water, irrigation should follow the actual crop water demands. However, direct measurements of transpiration are scant, and indirect methods are commonly applied; e.g., the Penman-Monteith (PM) equation that integrates physiological and meteorological parameters. In this study, the effects of environmental conditions on canopy resistance and water loss were experimentally characterized, and a model to calculate palm tree evapotranspiration ETc was developed. A novel addition was to integrate water salinity into the model, thus accounting for irrigation water quality as an additional factor. Palm tree ETc was affected by irrigation water salinity, and maximum values were reduced by 25 % in plants irrigated with 4 dS m-1 and by 50 % in the trees irrigated with 8 dS m-1. Results relating the responses of stomata to the environment exhibited an exponential relation between increased light intensities and stomatal conductance, a surprising positive response of stomata to high vapor pressure deficits and a decrease in conductance as water salinity increased. These findings were integrated into a modified 'Jarvis-PM' canopy conductance model using only meteorological and water quality inputs. The new approach produced weekly irrigation recommendations based on field water salinity (2.8 dS m-1) and climatic forecasts that led to a 20 % decrease in irrigation water use when compared with current irrigation recommendations. © 2014 Springer-Verlag Berlin Heidelberg.

Freeman S.,Israel Agricultural Research Organization | Gamliel-Atinsky E.,Israel Agricultural Research Organization | Maymon M.,Israel Agricultural Research Organization | Shtienberg D.,Israel Agricultural Research Organization | And 2 more authors.
Acta Horticulturae | Year: 2015

Mango malformation disease (MMD) caused by Fusarium mangiferae severely affects the crop and is widely distributed in almost all mango-growing regions worldwide. Additional Fusarium species have also been reported to cause MMD. Since malformed inflorescences do not bear fruit, MMD is a major constraint to crop production in affected areas. Symptoms of MMD include hypertrophy of young shoots, shorter internodes, dwarfed malformed leaves and an overall tightly bunched appearance of the shoot, while inflorescence malformation include short, thick and branched axes of the inflorescence, larger flowers with increased numbers of male and hermaphrodite flowers that are either sterile or eventually abort. Malformed inflorescences serve as the primary source of spores which disseminate passively in the air as conidia are blown or fall from dry malformed inflorescences as dry debris. Conidia land on the foliage and reach the infection site, namely, the apical bud. Systemic colonization and infection by the fungus was not evident for this host-pathogen interaction, since (i) there was no infection via roots or survival in soil, (ii) there was no continuum of colonization via the vascular tissues, and, (iii) the pathogen is concentrated within apical and lateral buds, only at but not between the nodes. No effective control methods have been reported to date. The airborne nature of dissemination and infection of buds suggests that protection of buds from infection when inoculum prevails may be a plausible method for disease control from season to season. Field experiments conducted over a number of seasons in different experimental regions in Israel indicate that disease severity can be reduced based on sanitation by removing inoculum density within infected panicles and with timely applications of effective fungicides.

Silber A.,Israel Agricultural Research Organization | Israeli Y.,Northern RandD | Levi M.,Northern RandD | Keinan A.,Northern RandD | And 6 more authors.
Agricultural Water Management | Year: 2012

The performance of 'Hass' avocado trees grown in lysimeters under different irrigation regimes obtained by manipulating drip irrigation frequency and root volume was examined. The experimental design comprised six treatments (3×2) with three irrigation frequencies and two container volumes (100- and 200-L). The three irrigation frequencies were: pulsed irrigation (10-20min every 30min) throughout the day (Irg1), one daily irrigation event beginning at night and terminated in the morning every day (Irg2) and one irrigation event every two days (Irg3). Irrigation management induced significant differences in water availability in the root zone and subsequently, the diurnal and periodic water uptake. Water uptake of trees in the Irg1 treatment closely followed changes in the meteorological conditions (air temperature, pan evaporation and vapour pressure deficit) while that of trees in the Irg2 and Irg3 treatments was depressed by intermediate and severe water stress, respectively. The experimental treatments had little effect on the vegetative growth, flowering or fruit-set processes. However there were significant treatment differences on fruitlet abscission and accordingly, on fruit yield. Black spots initiated from the seed became apparent on some of the fruits at the beginning of June, and about two weeks later an intensive abscission of fruitlet begun that ended at the beginning of July. The abscission was more intense in the 100-L than the 200-L containers, in the following order: Irg3>Irg2≥Irg1 regardless of the container volume. Net CO 2 assimilation during periods of fruit growth decreased in trees exposed to moderate or severe water stress (Irg2 and Irg3, respectively) and therefore, it is plausible that fruitlet abscission resulted from carbohydrate stress. Improvement of water and nutrient availability, especially in periods where the activity of the root system was weak as a result of low carbohydrate supply presumably played a dominant role in seeds or fruit function. © 2011 Elsevier B.V.

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