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The widespread practices of viniculture (the study of production of grapes for wine) and oenology (the study of winemaking) affirm the generalization that grapevines have fewer problems with mineral deficiency than many other crops. Only occasionally is the addition of iron (Fe), phosphorus (P), magnesium (Mg), and manganese (Mn) supplements to the soil needed. Addition of potassium (K), zinc (Zn), and boron (B) to the soil is more common. And, of course, nitrogen (N) is critical for the production of proteins. Over the years, various transition metals (metals in groups three through twelve [3– 12] of the periodic table, Appendix 1) have been shown to be generally important. These groups include iron (Fe), magnesium (Mg), manganese (Mn), zinc (Zn), and copper (Cu). Many metals are bound to organic molecules that are important for life. Some of the metals, such as copper (Cu) and iron (Fe), are important in electron transport while others, including manganese (Mn) and iron (Fe), inhibit reactive oxygen (O) species (ROSs) that can destroy cells. Metals serve both to cause some reactions to speed up, called positive catalysis while caus¬ing others (e.g., unwanted oxidation) to slow down (negative catalysis). It is not uncommon to add nitrogen (N), in the form of ammonium salts such as ammonium nitrate (NH4NO3), as fertilizer to the soil in which the vines are growing. It is also common to increase the nitrogen (N) content in the soil by planting legumes (legumes have roots that are frequently colonized by nitrogen-fixing bacteria). Nitrogen- fixing bacteria convert atmospheric nitrogen (N2), which plants cannot use, to forms, such as ammonia (NH3) or its equivalent, capable of absorption by plants. Nitrogen, used in plant proteins, tends to remain in the soil after harvest or decomposition. With sufficient nitrogen present in the soil the growth cycle can begin again in the following season without adding too much fertilizer. In a more general sense, however, it is clear (as mentioned earlier) that the soil must be capable of good drainage so the sub-soil parts of the plant do not rot and it must be loose enough to permit oxygen to be available to the growing roots. |
