Those with large succulent leaves need more water. Onions do not need as much water as carrots. Potatoes, tomatoes, beans and sweet corn have high water requirements. Plant age is also important. Vegetables that are half grown, but in the midst of vigorous growth, need more water than vegetable plants that are mature.
Potatoes are very sensitive to lack of soil water.
Tuber numbers are determined early in the season and are very sensitive to insufficient soil water. Tuber initiation occurs two to four weeks after the potato crop emerges, and insufficient water at this time decreases yield. Waterings must reach the plant roots. Dig furrows between plant rows about 4 to 6 inches deep. Mulch can be compost, straw, shredded newspaper or grass clippings.