Table grape is cultivated on a very wide range of soils, from sands to clays that can be of high or low fertility. It grows best on deep fertile soils that allow root growth up to 3 – 5m or more. Very heavy clays or very shallow soils, poorly drained sites, and soils with high concentration of salts or other toxins are not suitable for better production because of very poor availability of nutrients.
The aim of any producer is a high yielding, quality crop that satisfies the end user. There are a large number of viticultural factors which can influence this, many are within the control of the grower, under given climatic and soil conditions.
Table grapes are traditionally best grown between 34 – 49 degrees latitude in both the northern and southern hemispheres. They can also be grown at higher latitudes on sun-facing slopes at low altitudes or in the dry tropics where irrigation water is available. It grows better during long, dry, hot summer and cool winter. Maximum temperature of the warmest month should be above 18 – 20°C and in the coldest month it should be above freezing.
Temperatures below 17°C reduces rate of sugar accumulation and it prolongs ripening, while very high temperature and low humidity may reduce the rate of sugar accumulation. High humidity increases pest and disease risks. Rain or cloudy conditions during blooming can result in poor fruit set. Rain at maturity increases fruit rot. A long growing season is needed for table grape berries maturity.
Nutrient availability depends upon a range of factors mainly soil pH, nutrient concentration and ratio in the soil, rooting depth, soil water supply, and the use of cover crops, mulches or cultivation. Vines prefer neutral pH, though it can tolerate soil pH in the range of 4.5 – 8.5. For example, grape vines grown in soils above pH 7.3 are prone to iron chlorosis.