Mark Chien, Penn State University
For many years, soil chemistry was considered the most important part of the soil portfolio. Growers tried to maximize yields, so nitrogen content was essential to productivity. For growing fine wine, however, the formula has changed. Now, winegrape growers look for moderately fertile soils that do not promote an overly vigorous vine. It’s no surprise that grapevines can often be found on ground that was once deemed unsuitable for any other crop. Vines are tenacious plants and their roots will spread far and deep in search for water and nutrients. For this reason, they often do not require very much in the way of additional nutrients, except on the most inhospitable sites.
The addition of inorganic chemicals has been the primary method of ameliorating the soil since World War II. Essential macronutrients include nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and sulfur (S). Micronutrients include iron (Fe), zinc (Zn), manganese (Mn), copper (Cu), boron (B), molybdenum (Mo), and chlorine (Cl). Of these, N, P, K, Ca, Mg, Fe, Zn, and B are most often implicated in nutrient imbalance situations. All of these elements have important roles in vine metabolic functions and need to have minimum levels maintained. Considerable potassium is removed with the crop each year, and thus, may need to be replenished regularly. Some, such as boron, can also cause toxicity problems for vines if applied in excess. Too much nitrogen can exacerbate canopy management problems.
A soil test by a reputable lab is part of the standard site evaluation protocol. Remember, a test is only a set of numbers. The true value is in the proper interpretation of these results. For this, you should consult a vineyard soils expert. Amend the soil prior to planting. Other soil variables include soil pH and cation exchange capacity (CEC). These have an influence on nutrient availability to the roots as well.
Reviewed by Eric Stafne, Mississippi State University
and Bruce Bordelon, Purdue University