Vegetable growers understand that water deficiency decreases yield, reduces fruit marketability and quality, and, in extreme case, causes plants to die. In Indiana, we are typically not short of precipitation during growing seasons; rainfall is the primary water source. However, concentrated heavy rains and extended dry periods are not desirable for vegetable production. Severe losses can happen if an extended dry period occurs at the plant growth stages most sensitive to drought stress. This is typical during the flowering and fruit set stages of most fruiting vegetables.
To avoid water deficiency, most vegetable production needs irrigation. Efficient irrigation scheduling can be complicated because the irrigation frequency and amount of water vary according to crop types, growth stage, current soil moisture, soil types, and weather conditions.
Evapotranspiration (Et)-based irrigation is one of the methods in scheduling irrigation. This method determines irrigation based on weather conditions and crop growth stages. At Southwest Purdue Ag Center (SWPAC) and Pinney Purdue Ag Center (PPAC), we demonstrate the Et-based irrigation scheduling on several fruiting vegetable crops. In other articles, we will explain the exact method of how we schedule the irrigation using this method. Here, we are updating what we have observed from the demonstration.
Tomato, pepper, eggplant, watermelon, and cantaloupe are planted on plastic-covered beds with drip tape. They grow on beds side-by-side with and without irrigation. To understand how well the irrigation scheduling performs, we installed sensors 12 inches deep that constantly monitor soil moisture levels.
At SWPAC, we conduct the demonstration in a field with sandy loam soil. We planted the crops on May 16. There were several heavy rainfalls in the last week of May. On the irrigated beds, the first irrigation event occurred on May 31, and then irrigation occurred again every 2-3 days based on the Et value. The beds were irrigated about 3 hours at every event. The soil moisture stayed at a constant level on the beds with irrigation, while the moisture level gradually decreased on the beds without irrigation (Figure 1). Tomatoes are setting fruit at the first flower cluster, and peppers and eggplants are at blooming stages. Watermelon and cantaloupe are in vegetative growth and early blooming (Figure 2). We can not observe any difference between irrigated and non-irrigated beds of all the crops at this point despite crops growing at the different soil moisture levels. An interesting note, tomatoes have curling leaves on both irrigated and non-irrigated beds. The tomato cultivar is Mountain Spring which tends to show the leaf symptom. It is a typical plant response to the environment, and often occurs after suckers are pruned off.
Figure 1. Soil moisture levels between irrigation and non-irrigated tomato bed at SWPAC.
Figure 2. Crop stages of the vegetables in the irrigation demonstration at SWPAC.
Funding for project Improve Drip Irrigation Management for Vegetables and Melon Production in Indiana was made possible by the Indiana State Department of Agriculture through grant A337-22-SCBG-21-003. Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the ISDA.