Managing Vegetable Irrigation

May 29, 2023

Water management is crucial for highly productive vegetable farms. Because of high intensity crops, irrigation is often used, whether it is overhead or drip irrigation. Either way, early morning is a generally a good time to irrigate. That way, the crops have the moisture they need during the heat of the day, but don’t have an excess of water during the night when they would rather be a little drier. It is usually not a good idea to put plants to bed with wet feet, or with excessively wet foliage, as that promotes disease stress.

Some crops like wetter soil than others. Onions and garlic are a few examples; these crops do really well with more moisture as compared to the average crop and, under normal circumstances, can be irrigated 2-3 hours per day during the bulbing stage. This has a tremendous impact on onion and garlic production. Yellow tips on garlic is quite often a water deficiency, although nitrogen and other nutrients can certainly contribute.

Potatoes also can use a lot of water, and when adequate soil moisture is combined with adequate levels of magnesium, sulfur, molybdenum, and boron, it is likely that the Colorado Potato Beetle will not be an issue.

Zucchini likes a lot of water, and when combined with heat, will typically make for a very productive patch.

Tomatoes also use a lot of water, but it needs to monitored and managed very carefully. If it gets too dry and then a lot of water is added to make up for it, the tomatoes will likely crack.

Other crops, such as sweet potatoes and raspberries, do not like the soil so wet. They prefer it a little drier.

Regardless, all crops need some moisture to thrive. Water improves the uptake of some nutrients, such as calcium and potassium. It also improves biology which make minerals available to your crops. And interestingly, moist soil helps keep the soil in the reduced form, which helps the uptake of trace mineral metals such as manganese, cobalt, iron, and copper.  As a grower, you should constantly be checking the soil moisture with your hand. With some practice, you should learn about what seems to be right for your farm.

Several other interesting points about moisture management involve minerals. Potassium has often been called the poor man’s irrigation, because it is involved in using water efficiently. Plants need adequate levels of potassium or they fail to close their stomata on a hot day, and in such a way will use water inefficiently, making them more susceptible to heat stress.

The Nitrate form of nitrogen also uses water very inefficiently. When nitrate numbers are high within plant sap, it may take as much as 3 times more water. This makes for some very watery cells that don’t hold up well in storage.

Another interesting one is Manganese. Manganese is completely responsible for water hydrolysis, which makes water available for use in photosynthesis and sugar production. This means that having adequate levels of manganese is critical for high brix content.

In summary, all these points are interesting. But perhaps the point that I wanted to bring out the most is the timing of water applications. I have personally experienced differences in taste and crop health that I have attributed to differences in moisture management. For some of those more sensitive crops, too much water does affect flavor, as does too much nitrate in all crops.

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Source: Melvin Fisher | Sponsored by Keystone Bio-Ag LLC