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Uri Yermiyahu, Alon Ben-Gal, and Pinchas Sarig

Table grape production has recently become popular in arid and semiarid regions where conditions of salinity and excess boron (B) can be prevalent. This study addresses B toxicity in grapevine to define toxicity symptoms and evaluate growth, production, and B accumulation. The effect of excess B on grapevines (Vitis vinifera L. cv. Sugraone) was evaluated in a 4-year study in Israel's Jordan Valley. Vines were grown in 60-L perlite-filled containers and irrigated with complete nutrient solutions with four B concentrations: 0.03, 0.12, 0.21, and 0.31 mm. Vines were monitored for growth, yield, and B accumulation. Boron accumulation in leaves correlated with B toxicity symptoms that materialized as chlorosis and necrosis of leaves beginning at their margins, reduced leaf size, and reduced internodal distance between adjacent leaves. Boron accumulated in grapevine leaves linearly as a function of increased B in irrigation solution with time and with age of leaves. The highest B levels were found at the end of each season and in the oldest leaves. No long-term (multiyear) effect of exposure to B was observed because similar accumulation patterns and levels were found in each year of the experiment. Hence, consistently sampled diagnostic leaves and time of sampling for B analysis is seen to be critical to provide valid comparisons between vines or over time. Boron supply influenced vine growth. At low levels of B (0.03 mm), canopy development was restricted but trunk size was not. At high levels of B (0.21 and 0.31 mm), substantial visual symptoms of B toxicity were observed, and the rate of trunk growth was reduced, but pruning biomass was not influenced. Despite severe visual toxicity damage and reduced overall growth rates, commercial fruit yield of the vines remained unaffected by high environmental B levels.

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Hagai Yasuor, Alon Ben-Gal, Uri Yermiyahu, Elie Beit-Yannai, and Shabtai Cohen

Producers of horticultural products face new and growing standards regarding food quality and safety as well as environmental responsibility and sustainability. The objective of this research was to reduce environmental pollution by increasing nitrogen use efficiency (NUE) in vegetables without negatively affecting fruit yield or quality. Bell pepper was used as a case study for intensive vegetable cropping. Pepper cultivars with different vegetative vigor were drip-irrigated with solutions containing 9.2, 56.2, 102.3, and 158.5 mg·L−1 nitrogen (N). Fruit yield, quality, and nutritional value were measured. Nitrogen balance was determined by quantifying N in soil and in plant tissues. Maximum yields were found when peppers were irrigated with 56.2 mg·L−1 N. Nitrogen concentrations of 102.3 and 158.5 mg·L−1 N loaded 400 and 800 kg·ha−1 N into the environment, respectively, whereas for the 56.2 mg·L−1 N concentration, N was almost completely taken up and used by the plants. Nitrogen treatments had no significant negative effect on pepper fruit physical or chemical quality parameters including sugar content and acidity. Reduced N application did not affect nutritional quality components of the pepper fruit such as β-carotene and lycopene content or total antioxidant activity. The vigorous cultivar used N more efficiently. The results demonstrate how the environmental impact of intensive agriculture can be minimized without harming fruit yield or quality by reducing N application level and adopting cultivars with improved N use efficiency.

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Arnon Dag, Ran Erel, Alon Ben-Gal, Isaac Zipori, and Uri Yermiyahu

The global production of olives (Olea europaea L.) has increased rapidly over the last decade as a result of the expansion of orchards with high tree densities. Most olives are propagated from rooted cuttings. The present study evaluated the propagation rate of rooted cuttings as a function of the nutritional status of the stock trees. Rooting ability was evaluated for cuttings taken from container-grown stock plants exposed to eight concentrations of nitrogen (N) (ranging from 0.4 to 14.1 mm), seven concentrations of phosphorus (P) (ranging from 0.01 to 0.62 mm), and five concentrations of potassium (K) (ranging from 0.25 to 5.33 mm). Increases in N level negatively affected rooting rate and cutting survival. Propagation success was increased threefold as N in irrigation water was reduced from the highest to the lowest treatments. Enhanced root development under low N concentrations resulted in higher root weight compared with the high N concentrations. The high concentration of N fertilization negatively affected the propagation rate but was not reflected in N concentration of diagnostic leaves. There was, however, a significant negative correlation between N in twigs and propagation rate. Regarding response to K concentration, no effect was found on rooting rate or cutting survival. Except for reduced rooting at the lowest concentration, P had a negligible effect on rooting rate. The experimental results indicate the need to avoid overfertilization of olive stock trees with N to promote successful propagation.

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Ran Erel, Arnon Dag, Alon Ben-Gal, Amnon Schwartz, and Uri Yermiyahu

The independent effects of nitrogen, phosphorus, and potassium concentrations in the irrigation solution on flowering and fruit set in olive trees (Olea europaea L. cv. Barnea) were studied in a container experiment. Treatments included eight levels of N ranging from 0.4 to 14.1 mm, seven levels of P ranging from 0.01 to 0.62 mm, and seven levels of K ranging from 0.25 to 5.33 mm. At low environmental concentrations of each of the minerals, additions led to large increases in their concentrations in leaves, and as the environmental concentrations became high, relative increases in leaf accumulation were reduced. Availability of N, P, and K was found to influence flowering intensity in the olive trees. Fruit set was affected by N and P, but not K levels. Total fruit load of olives was shown to be a function of flowering level multiplied by fruit set. The final number of olives per tree increased appreciably as leaf P and K increased from minimum levels, and relative increases in fruit load tapered at the highest measured leaf concentrations of the minerals. Maximum fruit load was found corresponding to ≈0.06 mol·kg−1 P and close to 0.35 mol·kg−1 K in leaves. Fruit load increased to a maximum as leaf N increased from 0.7 to 1.3 mol·kg−1 and then decreased as leaf N increased to 1.5 mol·kg−1. The findings indicate that each of the macronutrients plays a fundamental role in processes affecting olive tree productivity.