Agricultural researcher Tom Geiger on his current experiment, circa May and June 2016.

My current project has two parts: vegetable variety trial and irrigation equipment evaluation. The variety trial part is comparing three different okra varieties to see which one is the best for the local conditions. As far as vegetable variety trials go, it's pretty small. Larger universities tend to have agricultural experiment stations all over their state and conduct variety trials with hundreds of varieties at multiple locations. The university I work for has a small research program and the island is not very big, so variety trials can't be conducted on the same scale here. But they are still important to local farmers. This okra variety trial is a continuation of another trial we did with seven varieties a couple years ago.

The okra is being irrigated with four different kinds of plastic drip irrigation lines with emitters spaced every foot. We are comparing pressure-compensating and non-pressure-compensating drip lines. Pressure-compensating lines will have the same flow out of each emitter within a certain pressure range. This is important if you're planting on a slope, because you will be irrigating the same amount at the bottom of the slope as you are on top. Non-pressure-compensating drip lines increase flow as pressure increases, so the bottom of a slope will always receive more irrigation than the top, decreasing irrigation efficiency and uniformity in your field.

In this study there are two drip tapes that are non-pressure-compensating, a drip tape that is pressure-compensating, and a drip tube that is also pressure-compensating. The difference between drip tape and drip tube is the wall thickness. Drip tubes are thicker, so they last longer, but they also take up more space on a pallet. This is important to farmers here on the island because it is expensive to ship things by boat.

Until recently you could only find pressure-compensating emitters in heavy-wall drip tubes. Now there are some thin-wall drip tape products on the market that have pressure-compensating emitters. We are testing these different products under field conditions and in the lab and comparing our results to the manufacturer's' specifications. This is useful to farmers in general and I think is especially useful to farmers here, who are still using non-pressure compensating drip irrigation and may not be aware of all the different products there are on the market. Besides wall thickness and whether or not they are pressure-compensating, all the irrigation equipment we are using have the same specs.

We have no rivers or streams on the island. All fresh water comes from wells, harvested rainwater, or desalination. Water conservation is especially important here and in island communities in general. One goal of this project is to encourage local farmers to increase their irrigation efficiency by switching to pressure-compensating drip tapes.

As for the moisture sensors, these are being used to compare soil volumetric water content in each plot. The sensors will help us to see if there are any differences in how each product irrigates, which wouldn't be apparent by just looking at the specs. They can also be used in an automated irrigation system by triggering irrigation once the water content drops below a certain threshold. This current project isn't automated but I am working on another project using sensors to control irrigation in hydroponic cucumbers. Sensor-based irrigation is increasingly popular, especially with larger farms and greenhouses.