This was a four-year study on the effects of N fertilizer timing and rate on vine N status, fruit composition and quality, and vine yield in four wine cultivars important to the San Joaquin Valley — Barbera, Grenache, French Colombard, and Chenin blanc. It was initiated as a follow-up to previous studies in raisin and table grape vineyards which demonstrated the influence of N fertilizer timing on N availability and utilization and possible improvements in N fertilizer efficiency. Similar studies are needed in wine grape vineyards to determine N timing response as well as effects on vine tissue N levels, fruit composition, and vine yields. N fertilizer treatments included budbreak (BB), berryset (BS), veraison (V), and postharvest (PH) timings at 50 lb. N /ac, BS at 100 lb. N/ac, and check, no N (CKO). N status, as determined by bloom and veraison petiole N03-N and NH4-N (inorganic N compounds) levels, varied among the cultivars and was influenced by rate (0, 50, and 100 lbs. N) and the proximity of fertilizer application prior to petiole sampling date. Grenache and Barbera were the high and low extremes, respectively, in vine N status and responsiveness to N fertilizer application; Chenin blanc and French Colombard were intermediate. Generally, CKO and BS100 were the high and low vine N status treatments through the experiment. PH50 resulted in bloom N levels equal to BB100 and sometimes higher than BB50, suggesting that postharvest timing was the most efficient in supplying N between budbreak and bloom. Otherwise, timing effects on vine N status were minor. Petiole N03-N was more sensitive than NH4-N to N fertilizer treatment differences. However, the sum of the two analyses (expressed as “total inorganic N”) provided the most clear separation among treatment differences and thus could be considered as a useful tool in grapevine N fertility research. Grape soluble solids was the most responsive fruit parameter to N treatment. Generally, N fertilizer tended to decrease soluble solids, irrespective of timing, and with the highest N rate of 100 lbs. resulting in the largest decrease. Titratable acidity differences were mostly inverse to soluble solids. Grenache was the only cultivar with significant yield differences due to N fertilization, suggesting a N-deficient status with this cultivar. All of the N treatments in Grenache, with the exception of V50, increased vine yield over CKO. This result, as well as other negative effects of the V50 treatment, ie.lower titratable acidity and higher pH in Grenache and more cluster rot in French Colombard and Chenin blanc, indicate that veraison may be the least desirable of the timings studied here. The detrimental effects of the high 100 lb.N treatment were also demonstrated, primarily through delayed fruit maturation and some increased cluster rot incidence. The bloom petiole N03-N levels reported here should provide supportive data toward establishing critical vine tissue levels in the wine cultivars studied here.
/wp-content/uploads/2017/09/AFV-Header-Logo.png 0 0 AVF /wp-content/uploads/2017/09/AFV-Header-Logo.png AVF1991-11-17 07:54:022017-11-17 07:55:05Improving nitrogen fertilizer efficiency in winegrapes