Fuente: WIPO "tomato" Disclosed herein are micro-sized aragonite compositions and methods for enhancing calcium uptake and overall plant health. The disclosure provides calcium compositions comprising particles of aragonite, preferably oolitic aragonite, that are mechanically reduced to micron or sub-micron dimensions to generate a highly bioavailable, rapidly dissolving calcium source suitable for foliar or soil application. The compositions may be incorporated into liquid suspensions, granules, coated fertilizers, seed treatments, or nutrient delivery systems, and may optionally include biologically active agents, growth stimulants, humates, or surfactants to further promote uptake. Methods of using the compositions to treat calcium deficiency, strengthen cell walls, reduce blossom-end rot, increase stress tolerance, and improve yield are also provided.