Effects of Foliar and Soil Boron Fertilization on Yield, Leaf Physiological Traits and Fruit Attributes in Rainfed Almond Orchards

Abstract

Boron (B) fertilizers are recognized as essential for ensuring yield and fruit quality. However, the importance of soil and foliar B fertilization in almond orchards under rainfed conditions is presently unclear. To address this literature gap, in the present study, the impact of soil and foliar application of B on leaf gas exchange, leaf photosynthetic pigments, yield, and fruit quality in almonds was investigated across three consecutive growing seasons. Boron fertilizer was applied to the soil at four rates (0, 1, 2, and 3 kg ha−1) in the presence or absence of foliar application (0.36 g L−1) of the same micronutrient. Borax pentahydrate was used as the B source. When compared to foliar B fertilization, the soil application of B positively affected the gas exchange parameters, mainly the net CO2 assimilation rate, stomatal conductance, and transpiration rate (percentage of gain between 15% and 80%), but did not influence the chlorophyll content. The almond yield and fruit characteristics were also enhanced (about 25–72%) in response to lower soil B fertilization rates. In the 3 kg ha−1 dose, B had an adverse effect on the yield and resulted in lighter fruits. On the other hand, foliar B fertilization did not benefit any of the evaluated parameters. Overall, these results suggest that, under the studied conditions, almond orchards do not respond to higher B rates in soil or foliar B fertilization.

Soil Quality Index of Young and Differently Managed Almond Orchards under Mediterranean Conditions

“…In addition, high values of carbonates, active limestone, and AB reduced the soil quality in the studied orchards because they can compromise crop development. In fact, a recent study showed that low soil boron contents enhanced almond yield in Portugal [45]. These results suggested that the evaluated soils could be adequate for almond production, but they require management actions to improve their quality to increase the sustainability of these agroecosystems, such as the application of organic amendments, as suggested by Villa et al [46].…”

Effects of Foliar Boron Application on Physiological and Antioxidants Responses in Highbush Blueberry (Vaccinium corymbosum L.) Cultivars

“…Both B toxicity and deficiency present similar symptoms in plants, including a decrease in photosynthesis, and efficiency of photosystem II, low transpiration rate and stomatal conductance, alterations in the activity of antioxidative enzymes, and increased lipid peroxidation [ 36 , 37 , 38 ]. On the other hand, optimal B supply exerted a positive effect on gas exchange parameters such as the net CO 2 assimilation rate and stomatal conductance in almond ( Prunus dulcis ) [ 39 ]. Similarly, in Zea mays plants, B application considerably improved growth, photosynthetic capacity, tissue B concentration, as well as the antioxidant defense system [ 40 ].…”