Drought-prone soils are usually high in sand, allowing them to be well drained and easily worked. Good water drainage is critical for preparing soil for early spring planting and reducing root diseases. Sandy soils are also easy to prepare for planting and shape into a bed, which is important to production of many fresh vegetables. Sandy soils, however, offer unique challenges.

Contamination of groundwater supplies has become a critical issue in recent years. Once contaminated, these water sources are difficult to clean, and effects can last for several years. Well-drained, sandy soils are prime candidates for groundwater contamination. The physical and chemical properties of sandy soils do not allow for good retention of moisture and nutrients. This is shown in their relatively low cation exchange capacities (CEC).

Sand particles are quite large, and provide a small surface-to-volume ratio, giving them a relatively small surface area for water and nutrients to attach to. This allows water and nutrients to easily move through these soils. Underlying soils on these sites are often even poorer in their retention ability. The result is that any water-soluble product (nutrients and pesticides) applied to the surface can have a fairly rapid trip to the water table.

A number of agriculture-related chemicals have been found in groundwater, but the most common problem may be an increase in nitrate content. This can be due to natural sources, but can also come for inadequate manure and nutrient management. If elevated nitrate levels are found in water supplies, the first place most people will look is agriculture. The best way to avoid this potential conflict is to use nitrogen (and all products) wisely, and be able to prove you have by keeping good records.

Since water moves so easily in and through sandy soils, growers have to be careful how they apply it. Unlike clay soils, surface runoff potential is low in sandy soils. Therefore, water can be applied more quickly, but needs to be applied more often. This is true for either overhead or drip systems.

Most sandy soils have permeability rates of 2 to 6 inches an hour. However, some sandy soils have permeability rates between 6 and 20 inches an hour. With rates this high, much of the water from large, single applications goes beyond the root zone, and anything beyond the root zone cannot be recovered and used by the plant. On these sites, it is better to irrigate with lesser amounts but more often. If your crop needs 2 inches of water a week, it would be better to apply two applications of 1 inch, rather than one single application of 2 inches.

Growers using drip irrigation also need to remember that the irrigated area is less than the total surface area. So an acre-inch of water has a much different meaning when using drip irrigation than it does using overhead.

Rapid permeability of sandy soils contributes to poor lateral movement of water. Growers using drip irrigation can choose irrigation tape with different flow rates and emitter distances. Heavier soils have good lateral movement, and can be irrigated with low-volume tape with a wider-spaced emitter. Sandy sites should be irrigated with shorter-distance emitters and/or high-volume tape.

When to irrigate and when to stop are important management decisions for economical and sound water use. Several ways of measuring available water, water-holding capacity, and water movement through the soil have been developed and are commercially available.

For nutrients to be available to plants, they have to be water-soluble, which makes them subject to moving to wherever the water moves. Proper water management is important for maximizing the plants’ use of nutrients and, therefore, maximizing your investment. Nutrients applied to heavy soils should be incorporated. This minimizes the chance for surface runoff in the event of heavy rains or over-irrigation. A number of growers probably have a story they can tell about the time they applied fertilizer and got a heavy rain that washed the fertilizer to the end of the row.

Growers using drip irrigation have the ability to apply nutrients on a more continual basis. However, if water is not well managed, the nutrients may not be efficiently used. Long drip-irrigation times on sandy soils can cause water to go beyond the root zone. When this happens, it carries any dissolved nutrients beyond the root zone, making them unavailable to the plant. This can lead to over-fertilizing followed by over-watering. Carried on long enough, this cycle will push nutrients closer to ground water. If this has happened to your sites, it would be good for you to rotate in a deep-rooted crop to utilize those nutrients that have gone beyond the root zone of your vegetable crop.