Unfolding boron dynamics at the scale of soil-water-fertilizer-crop systems in the tropics: from soil availability to plant requirements

Abstract

ABSTRACT Boron (B) is an essential element that limits crop productivity and quality in tropical regions due to its low availability. Rainfall regime influences B dynamics in soil, which, in turn, affects crop responses to B. Tropical soils are considered low in B if concentrations are less than 0.20 and 0.60 mg kg–1 for annual and perennial crops, respectively. The B availability in soil is governed by the soil’s pH, texture, organic matter (OM) content, cation exchange capacity, and source material. Plants’ uptake of B occurs passively, although it varies according to its availability in the soil solution. The presence of low- affinity (BOR1 gene) and high-affinity (NIP5;1 gene) transporters has been characterized. B deficiency can impair crop development due to its role in cell metabolism at the molecular, physiological, anatomical, and morphological levels. Both B deficiency and toxicity affect plant growth, highlighting the importance of monitoring B availability by assessing soil fertility to optimize crop performance and quality. Further study should examine the nutritional management of economically important crops using B sources with different solubility in water, application rates, particle sizes, placement, forms, and timing. The speculation that the range between B deficiency and toxicity is narrow may be misunderstood, especially when foliar diagnosis is still neglected. This review aims to understand B dynamics in tropical soils, its functions in higher plants cultivated in these regions, and how its deficiency and/or toxicity can affect agricultural production.