Irrigation Demonstration Update June 25 – Vegetable Crops Hotline

Irrigation Demonstration Update June 25

At Southwest Purdue Ag Center (SWPAC) and Pinney Purdue Ag Center (PPAC), we demonstrate irrigation impacts on several fruiting vegetable crops. Tomato, pepper, eggplant, watermelon, and cantaloupe are planted on plastic-covered beds with drip tapes. They grow on beds side-by-side with and without irrigation. We used two approaches to schedule irrigation, one bed is irrigated based on evapotranspiration (Et), and another bed is irrigated based on soil moisture sensors. More information about this demonstration can be found in the previous newsletter article

At SWPAC (Vincennes, IN), the crops were planted on May 16. There was little rain since the beginning of June. The soil was dried out without irrigation. On the unirrigated bed, soil moisture levels at 12’’ depth dropped from 25% to about 10%, while soil moisture was maintained between 20-27% on irrigated beds. How do the different soil moisture levels affect the plants?

A dramatic effect was observed on tomatoes. Recorded last week, tomatoes grown on the unirrigated bed had 49% fruit showed blossom end rot (BER) on the first flower cluster and 40% of fruit with BER on the second flower cluster (Figure 1). Less than 10% fruit showed BER on irrigated beds which suggests BER is closely associated with soil moisture, with dry conditions promoting the occurrence of BER.

Planted at the same time, peppers and eggplants set fruit later than tomatoes, about 1-3 fruit were set on each pepper and eggplant plant. We have not noticed differences between irrigated and unirrigated plants on peppers and eggplants.

The first fruit sets on cantaloupes have passed softball size and started to form netting. Toward the end of last week, we noticed cantaloupe leaves started to wilt in the afternoon on the unirrigated bed but not on the irrigated beds. Watermelons recently start to set fruit. We did not see plant wilt on watermelons, but the overall vine growth on the unirrigated bed was less compared to vine growth on the irrigated bed.

At the time of writing the updating article (June 25), close to 0.6 in. rain occurred in the weekend, and there is a chance of precipitation toward the end of this week. The rains will be greatly helpful to the dry conditions, although they cannot reverse BER on tomato fruits that already set. We are not sure if the rain is timely enough to avoid yield loss and/or quality reduction on other vegetables. We will continue the update as the season progress.

Figure 1. Tomato blossom end rot symptoms on the unirrigated bed at SWPAC. The initial symptom is light green at the blossom end with tissues staying firm.

Figure 1. Tomato blossom end rot symptoms on the unirrigated bed at SWPAC. The initial symptom is light green at the blossom end with tissues staying firm.

Figure 2. Crop stages at SWPAC: tomatoes set fruit at third or fourth flower clusters. Peppers and eggplants had 1-3 fruit sets. Photos were taken on June 27.

Figure 2. Crop stages at SWPAC: tomatoes set fruit at third or fourth flower clusters. Peppers and eggplants had 1-3 fruit sets. Photos were taken on June 27.

Figure 3. The unirrigated cantaloupe showed wilt symptoms in the afternoon. Watermelon did not show wilt symptoms, but overall vine coverage on the unirrigated bed was less compared to vine growth on the irrigated bed at SWAPC. Photos were taken on June 23.

Figure 3. The unirrigated cantaloupe showed wilt symptoms in the afternoon. Watermelon did not show wilt symptoms, but overall vine coverage on the unirrigated bed was less compared to vine growth on the irrigated bed at SWAPC. Photos were taken on June 23.

At PPAC (Wanatah, IN), crops were planted on June 6 in plastic-covered beds with drip tape. There was not much rainfall in the week prior to planting, but the day of planting there was 0.6 inches of rainfall. The first irrigation was applied to Et and sensor treatments on June 17. We applied enough water to fully wet the beds to field capacity. In the first week, beds with irrigation calculations based on Et were irrigated three more times. The tomato bed irrigated based on soil moisture sensor was irrigated twice and the watermelon bed with sensor not at all. Beds without any irrigation have been on a steady decline in volumetric water content. The tomatoes are just beginning to have their first flower cluster and the peppers and eggplants are still in early stages. The watermelons are vining with the longest vine being 28 inches long. We have not observed any differences in irrigated versus unirrigated beds besides the volumetric water content.

Figure 4. Crop stages at PPAC on June 24. From left to right: tomato, pepper, eggplant, watermelon.

Figure 4. Crop stages at PPAC on June 24. From left to right: tomato, pepper, eggplant, watermelon.

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.

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