Effects of the Annual Nitrogen Fertilization Rate on Vine Performance and Grape Quality for Winemaking: Insights from a Meta-Analysis

Table 2

Statistical summary of the vine production parameters and grape quality traits in the mineral N trials included in the database.

Data	Counts			Units	Mean ± 95% CI	Maximum	Minimum
	Articles	Trials	n
Grape yield	43	160	541	kg·vine^−1	3.7 ± 0.3	15.8	0.0
Pruning weight	22	119	346	kg·vine^−1	0.58 ± 0.04	2.00	0.01
Bunch number	26	66	253	—	29 ± 3	100	4
Bunch weight	24	62	232	g·bunch^−1	140 ± 10	380	20
Berry number	11	29	146	—	104 ± 7	213	34
Berry weight	31	80	302	g·berry^−1	1.45 ± 0.06	3.04	0.55
TSS	42	100	377	°Brix	20.6 ± 0.4	28.3	11.6
Titratable acidity	35	81	296	g·L^−1	7.3 ± 0.4	23.5	2.0
pH	29	77	281	—	3.45 ± 0.03	4.00	2.80
Malic acid	14	30	110	g·L^−1	3.5 ± 0.4	11.2	0.9
Tartaric acid	16	35	137	g·L^−1	4.3 ± 0.5	9.4	0.1
Anthocyanins	13	32	117	mg·L^−1	1600 ± 300	5200	30
Polyphenols	11	27	94	mg·L^−1	800 ± 300	4200	10
YAN	20	53	165	mg·L^−1	120 ± 10	600	20

n = number of collected records per variable; CI = confidence interval; TSS = total soluble solids; YAN = yeast assimilable nitrogen.