Effects of meteorological factors and fertilization on mineral element contents and berry quality in Cabernet Sauvignon

Abstract:【Objective】To provide reference for the realization of rational nutrient fertilization and high-quality production of Cabernet Sauvignon, the relationships between mineral elements contents and berry quality of Cabernet Sauvignon were investigated, and the main elements affecting the quality of Cabernet Sauvignon were screened.【Methods】With Cabernet Sauvignon as the test material, 5416 formula ertilization treatment was carried out for 3 consecutive years, and the element contents, basic physicochemical indexes and polyphenols content were studied in different growth stages/tissue parts treated with 16 formula fertilizers. The 5416 formula fertilizer refered to 5 factors (N, P, K, Ca and Mg), and 4 levels (multiples of the basic dosage of each fertilizer raw material per hectare, namely 0 times, 0.5 times, 1 times and 1.5 times), totaling for 16 treatments. The formula fertilizer was based on the yield tar-get of 7500 kg berry per hectare, and the basic dosages of each fertilizer raw material per hectare in the 5416 trial were set as follows: N 124.5 kg, P2O5 46.5 kg, K2O 112.5 kg, CaO 112.5 kg and MgO 46.5 kg. Based on Topsis analysis, each quality index was comprehensively evaluated to form a quality index (CI). According to the distribution characteristics of single element content, the orchards with high- CI were divided, and the nutritional diagnosis of low-CI orchards was carried out, and the fertilization plan and precautions were preliminarily formulated.【Results】The effects of different fertilization treatments on the quality in different years were significantly different, and the extreme values of the contents of phenolic substances and quality indexes had obvious tissue specificity between years. There was no significant difference in the average spike weight among treatments in 2018 and 2019, which were 417.8 g and 430.6 g, respectively. The average spike weight of each treatment in 2020 was significantly lower than that in 2018 and 2019 by 58.1% and 59.3%, respectively. The fertilization treatments with the high-est TSS contents from 2018 to 2020 were T14, T2 and T2, which were 22.7%, 26.5% and 24.3%, respec-tively. The fertilization treatments with the highest skin/fruit ratio in 2018-2020 were T8, T16 and T12, respectively, and the lowest fertilization treatments in 2018 and 2019 were T3. The fertilization treatments with the highest seed/fruit ratio in 2018—2020 were all T6, and the fertilization treatments with the lowest values were T4, T3, and T5, respectively. The distribution ranges of seed number in 2018— 2020 were 47.0 (T7)-59.0 (T4), 50.0 (T12)-64.0 (T16), 51.0 (T6)-66.0 (T1). The rainfall from May to June in 2018 and 2020 was 195.7 mm and 191.9 mm, respectively, and the rainfall in August in 2018 and 2020 was 217.0 mm and 142.4 mm, respectively. The average monthly increase in effective accumulated temperature before August was 50.3% and 81.6%, respectively, and the average decrease after August was 75.1% and 46.6%. The overall weather tendency in 2019 was fast heating, slow cooling, with an average increase of 113.2% before July and an average decrease of 31.2% after July. In addition, the total rainfall in 2018-2020 was 515.2 mm, 238.4 mm and 488.8 mm, respectively. The total effective accumu-lated temperature from 2018 to 2020 was 2 338.5 ℃, 2 291.0 ℃ and 2 092.9 ℃, respectively. The overall weather tendency in 2018 and 2020 was slow warming and fast cooling. Effective accumulated temperature (T) and rainfall (P) were one of the main factors causing interannual differences in quality under the same fertilization conditions. The amount of all phenolic substances (skin/seed total phenols, anthocyanins, peel/seed total flavonoids, peel/seed flavanols), skin/seed tannins) were significantly or extremely significantly and positively associated with the T/P value. The inflorescences/berries (_F), leaves (_L) and petioles (_P) were collected at full-bloom stage (FBS), veraison stage (VS) and maturation stage (MS) to determine the total amount of N, P, K, Ca and Mg. In leaves, N/Ca at full-bloom stage and Mg at full-bloom stage/maturation stage were significantly or extremely significantly and positively correlated with all phenolic substances. In petiole, P/Ca/Mg at full-bloom stage, P/Ca at veraison stage, and Mg at maturation stage were all significantly or extremely significantly and positively correlated. Based on the principle of the strongest correlation, FBS_L_N, VS_P_P, FBS_F_K, FBS_F_Ca, FBS_F_Mg can be selected as the plant nutrition diagnostic factors of Cabernet Sauvignon quality index in Penglai production area. The critical value of high- CI and low- CI orchards should be selected as 0.540 0, among which there were 14 high-CI orchards, accounting for 29.2% of the total sampling orchards. According to the range of element contents in high-CI plants, the appropriate values of the above nutritional diagnostic factors were determined as follows: N (12.9-31.3) mg·g^-1, P (4.0-11.6) mg·g^-1, K (6.4-35.9) mg·g^-1, Ca (15.7-69.9) mg·g^-1, and Mg (3.3-18.7) mg·g^-1. The descending order of fertilizer requirements for Cabernet Sauvignon low- grade orchards is: Mg＞K＞Ca＞P＞N, among which Mg, K and Ca contents are relatively low. In order to obtain Cabernet Sauvignon with high quality index, the recommended fertilizer rates per hectare are: N 186.8 kg, P2O5 70.0 kg, K2O 112.5 kg, CaO 112.5 kg and MgO 0 kg.【Conclusion】The management of water and fertilizer in an orchard was strengthened to improve the absorption of Mg by the tree. The application of other fertilizers should adopt the principle of small amount and many times, to avoid the season with large rainfall.