Yield, quality suffer quickly Irrigation is vital to quality vegetable production. If anyone was unsure of that statement, recent droughts should have convinced them. Drought seasons will be made and moderate seasons will be improved with irrigation.

Vegetables are 80 to 95 percent water. Think of vegetables as packages of water with flavoring and vitamins.

Since they contain so much water, it stands to reason their yield and quality suffer quickly from drought. If water shortages occur early in the crop's development, maturity may be delayed and yields are often reduced.

If a moisture shortage occurs later in the growing season, quality and yield will be reduced.

Growers who currently have irrigation capacity must decide when to start. Unfortunately, we often wait too long to begin, thinking that it will rain tomorrow. This can result in the portion of the crop that gets irrigated last being in severe stress before irrigation.

Another common problem is trying to stretch the acreage that can reasonably be covered.

Both of these practices result in part or all of the field being in water stress. It is better to do a good job on a portion of the crop than a poor job on all the acreage.

So, how quickly can drought stress begin to hurt a crop?

It depends on the current conditions, but it may occur in as little as two or three days following a one inch rain on some crops.

A good rule of thumb is about one-third inch of evaporation per day in the summer. However, on near 100 degree days evaporation has been about one-half inch per day. This means frequent irrigation is necessary for maximum yield.

The crop, stage of growth, and soil type are also important considerations.

Drip irrigation is one option that should be explored to help with the above mentioned timing and frequency problems. Drip irrigation is most often associated with black plastic production, but may also be used on bare ground.

Some advantages of drip include water placed directly near the roots, does not wet the foliage and ease of starting the system once in place.

Research on watermelon irrigation comparisons has shown highest yields with black plastic and drip irrigation followed by bare ground drip or overhead irrigation.

The test results indicate that irrigation in any of the forms mentioned above can increase yields 25 to 50 percent. Other vegetable crops would respond in a similar manner.

Many smaller growers may not have water sources readily available and, therefore, feel they have no options. However, putting down a well is an option in most locations. Even if the well will not supply adequate water to irrigate from, it probably will provide enough water to recharge a pond.

Then, there is the issue of initial cost. Irrigation is not a cheap input. However, consider the cost of not having irrigation this past summer if you farmed in the Southeast.

In many fields it meant having a crop to harvest or not. From that perspective, the real question is not can I afford irrigation, but can I afford not to have irrigation. As always, the economics of any irrigation source needs to be examined. The bottom line, of course, is profitability.

Growers will have an opportunity to sharpen their irrigation skills at the Irrigation Workshop scheduled during the Southeast Vegetable and Fruit Expo and AgTech 2000. The joint conference will take place Dec. 11-13, 2000 at the Sheraton Greensboro Hotel at Four Seasons in Greensboro, N.C.

Educational sessions on vegetables and precision agriculture along with an extensive trade show will be held throughout the three day event.