Shade Cloth Can Increase Tomato Yields
Some interesting research work from Jerry Brust, UME Vegetable IPM Specialist
(re-printed from article by Jerry in the UDEL Weekly Crop Update- Aug. 26, 2016)
I have been experimenting with using shade cloth in tomato over the last 5 years and they have worked remarkably well in increasing the marketable yields of many different cultivars of tomatoes by 20-50%. I use a 30% filtering shade (using any more than 30% tends to reduce yields and size of tomato fruit). The shade cloth is draped over the top of the tomato stakes and held down at both ends (Figure 4). I know this does not seem practical, but only the top ¼ of the plant needs to be covered (not shown) which means a grower could use shade cloth with a 4 ft width and as long as they wanted it to be. The shades can be used over and over for many years; the ones I am using have been in use now for 5 years. The shade cloth helps tomato plants come through very stressful weather conditions, i.e., high temperatures with high dew points and even heavy rains in much better shape than plants that were not covered.
Figure 4. Shade cloth over a section of tomato row
Figure 5 shows part of a row (with the red line) that had been covered with shade cloth for six weeks compared with the row next to it which had not – same cultivar planted on the same day. I arbitrarily selected that one section of row for the shade cloth in June. You can see how much better those plants that were covered look than the ones that were not covered. The benefit of using the shades is an increase in quality and size of tomato fruit, rarely in the number of fruit.
Figure 5. Part of tomato row (with red line) that was covered with shade cloth vs others that were not
Figure 6 shows harvest bins of tomato fruit with the bin on the left from plants that were covered from the end of June through July while the bin on the right was from plants (same cultivar) not covered. These experiments were replicated 4, 6, and even 8 times in the field over several years and the results were always the same – an increase in marketable yield each year. Some years it was an 18.9% increase and some years it was a 47.7% increase. Once plants are covered, the shade cloth can stay on the rest of the season until harvest. We sprayed through the shade cloth with fungicides and insecticides. Foliar diseases were reduced for plants under shade compared with plants outside shade. I am not suggesting a grower would shade an entire field, but you might select a few of your cultivars that bring a very good price, but are prone to producing ugly tomatoes during stressful weather conditions and shade those.
Figure 6. Harvest bins of tomato fruit; bin on left from plants covered with shade and bin on right from plants that were not covered.