Distribution of major nutrient elements in ‘ Kyoho’ grape organs across phenological stages

Rational and precise fertilization is essential for sustainable grape production, yet systematic, long-term data on the accumulation and distribution of major nutrient elements—particularly calcium (Ca) and magnesium (Mg)—in ‘Kyoho’ grapevine (Vitis labrusca × Vitis vinifera) remain limited. This study aimed to quantify the seven-year dynamics of nitrogen (N), phosphorus (P), potassium (K), Ca, and Mg accumulation and distribution among different plant organs at seven key phenological stages. Four-year-old ‘Kyoho’ grapevines were subjected to whole-plant destructive sampling at seven growth stages over seven consecutive years (2012–2018). The concentrations of N, P, K, Ca, and Mg in roots, trunks, perennial shoots, annual shoots, leaves, petioles, and fruits were determined by automatic Kjeldahl and inductively coupled plasma optical emission spectrometry methods, and data were analyzed using one-way analysis of variance with least significant difference test. Macronutrient accumulation increased steadily throughout the growth cycle, with significant differences in distribution among organs at different stages. During budding to seed development, leaves and annual shoots were the primary sinks. From seed development to harvest, fruits accumulated the majority of nutrients, with potassium distribution reaching 77.36% at harvest. Post-harvest, nitrogen, phosphorus, and potassium refluxed from leaves to perennial storage organs, while calcium was predominantly allocated to leaves with limited fruit mobility. These results demonstrate that nutrient management must be equilibrated according to stage-specific requirements.