Grapes

Vineyards require sixteen nutrient elements from air, water, and soil to produce a crop. Yield and quality may be reduced even when nutrient deficiency symptoms are not obvious. Nutrient management is a positive step towards the goal of maximum vineyard profit.

1. Grapes originated in a semi-arid climate and prefer a soil pH of 6.5 to 7.0. Soil fertilizer applications will be more efficiently used by the vine at this pH range. The beginning of a professional nutrient management program is to maintain the soil pH at optimal levels. A recent survey has shown that 29% of soil tests in California have pH readings below 6.0.

2. Nutrients should be applied only when leaves are present on the vines.

3. Pounds per acre of nitrogen, phosphorus, and potassium removed by ten tons of grapes:
   
   Nitrogen 48
   Phosphorus 8
   Potassium 64
   
   Actual amount of nutrients applied should be adjusted upward for sandy soil or furrow irrigation. These numbers assume all leaves and pruned canes are returned to the soil.

4. Calcium is essential for berry cell wall development.  Calcium also aids in cell division, mitigates stress, and improves both soil structure and soil water penetration. 

5. Nutrient application timing is critical for use efficiency, quality, and yield. Early spring growth and flowering uses nitrogen that has been taken up by the vine immediately after the previous fall harvest. Nitrogen applied between bloom and verasion (berry softening and coloring) is used for the current season crop. Nitrogen and potassium applied between verasion and harvest has been implicated in reduced grape quality.
   
   As with any fertilizer application, consult soil tests, leaf analysis, agricultural extension office, or other advisory services to select a program to meet local crop and soil conditions.