Abstract:

The aim is to lay a foundation for improving the quality of Merlot fruit and guiding precise fertilization in orchards. Taking Merlot grapewine in Yantai，Shandong Province as the test material，combined with the“5416”formula fertilization program from 2019 to 2021，principal component analysis （PCA）was used to evaluate 14 quality indexes of fruit at maturity stage，including 100 grain mass，soluble solid matter，ratio of skin to fruit，ratio of seed to seed，number of grains，total phenols，anthocyanins in peel，total flavonoids in peel and seed，flavanols in peel and seed，and tannins in peel and seed. PCA results show that T11 treatment（N 124.5 kg · hm^-2，P₂O₅ 46.5 kg · hm^-2，K₂O 0 kg · hm^-2，CaO 56.3 kg · hm^-2 and MgO 69.8 kg · hm^-2）had obvious effect on improving the comprehensive quality of Merlot grapewine. Correlation analysis was used to determine N in germination stage，P in maturation stage，K in maturation stage，Ca in maturation stage and Mg in germination stage distributed in 0-40 cm as soil nutrient diagnostic factors for anthocyanins. Plant nutritional diagnostic factors for anthocyanins were determined：N of petiole at veraison stage，P of inflorescence at full-bloom stage，K of leaf at full-bloom stage，Ca of leaf at veraison stage，Mg of petiole at maturity stage，Fe and Mn of leaf at veraison stage，Cu of fruit at maturity stage，Zn and B of inflorescence at full-bloom and Mo of leaf at full-bloom stage. The function model of diagnostic factors and anthocyanins was established by the method of component nutrition diagnosis（CND），and the diagnostic criteria for soil and plant nutrition of high-anthocyanin vineyards（high-quality vineyards）were finally established：The normalized value of anthocyanins corresponding to cumulative variance of soil element content > 0.6372；The normalized value of anthocyanins corresponding to the cumulative variance of plant medium and large elements content was > 0.8353；The normalized value of anthocyanin corresponding to cumulative variance of trace element content was > 0.8699. The diagnostic criteria for soil nutrition were N 0.06-0.21 mg · g^-1，P 0.08-1.17 mg · g^-1，K 0.05-0.23 mg · g^-1，Ca 0.52-8.51 mg · g^-1 and Mg 0.04-0.65 mg · g^-1. The diagnostic criteria of plant nutrition were N 5.38-11.00 mg · g^-1，P 5.45-10.88 mg · g^-1，K 6.73-39.75 mg · g^-1，Ca 35.57-68.83 mg · g^-1，Mg 9.30-24.63 mg · g^-1，Fe 233.93-398.83 mg · kg^-1，Mn 292.55-520.30 mg · kg^-1，Zn 29.03-73.65 mg · kg^-1，Cu 18.22-28.93 mg · kg^-1，B 20.52-35.13 mg · kg^-1 and Mo 0.78-1.85 mg · kg^-1. According to the abundance and deficiency characteristics of plants and soil elements in low quality vineyard（the normalized value of anthocyanins corresponding to the cumulative variance of the content of large and medium elements in the low-quality vineyards of Melot grapewine was < 0.8353；the normalized value of anthocyanin corresponding to the cumulative variance of soil elements was < 0.6372），it is recommended to apply P fertilizer to soil in a small amount and multiple times. Improve the water and fertilizer management system to improve the absorption capacity of K and Ca elements. The deficient trace elements are properly supplemented by foliar spraying.

Key words: wine grape, soil, plant, nutritional diagnosis, principal component analysis, quality