Fertilizers Used for Grape Vines

Nitrogen

• Nitrogen is one of the most important nutrients that needs to be present in the soil for growing grapevines. A lack of nitrogen will result in smaller, fewer vines, fewer leaves and, in turn, a slower photosynthesizing process and a smaller crop yield. Too much nitrogen is also a bad thing and can result in a thick covering of leaves that will shade the fruit and reduce its quality. Two weeks after planting the vines, apply a balanced 10-10-10 fertilizer to give the vines a well-rounded start to grow and establish themselves. After they have been established but before the vines begin to blossom, test the petiole of one of the newly formed leaves near the juncture where the grapes will form. This test can be done by your local college extension office. If the nitrogen is less than .7 percent, a nitrogen fertilizer will need to be added.

Potassium

• Potassium can be applied to grapevines in several ways. If the soil the plants are in is well-drained, potassium sulfate, potassium nitrate or potassium chloride can be added directly to the soil where it will be absorbed into the vines' roots. Because potassium compounds can be difficult for the soil to absorb, vines planted in clay-based soils will do better with an application of foliar spray -- otherwise, they may require twice as much potassium fertilizer applied to the soil before it reaches the roots. Potassium will keep the vines from developing stunted growth; yellowing around the outside of the grape leaves is also a sign of potassium deficiency and should be corrected immediately.

Phosphorus

• A phosphorus deficiency can be corrected with a phosphate or superphosphate fertilizer applied to the soil. In cases of severe deficiencies, this should be done before planting. Otherwise, an application of 10-10-10 fertilizer -- the same fertilizer recommended to keep a healthy nitrogen content in the soil -- can be applied each spring before the vines begin to develop their new growth for the season.

Warnings

• Grapevines can be very sensitive to chemicals, so it is important to look at exactly what the fertilizer contains. Some fertilizers have an herbicide that acts to kill new weeds that may grow, taking advantage of the nutrients added to the soil to gain a foothold in the garden. These fertilizers can damage the grapevines as well and should never be used. Vines are so sensitive that these fertilizers should not be used in areas nearby, where there is danger of the chemicals seeping into the soil around the vines, carried by runoff or the wind.