There are a lot of people who swear by drip irrigation for watering their gardens, and there are others who say to never use drip irrigation in your gardens. Let's tackle that question today and see what drip irrigation is, and if drip irrigation is actually the best way to go or not.
Drip irrigation is a means of distributing water to crops directly at the base of the plant and is often used in an effort to conserve water by not spraying water on the paths in between rows. This is done by having pipes or plastic tubes to direct the flow of water directly to the base of the plants instead of watering areas where your plants are not growing like pathways and in-between plants.
One of the benefits, in addition to the water savings, is that you are not watering areas where weeds will be growing, thereby limiting the amount of weed pressure that your plants will be having to compete with for nutrients within the soil.
Using drip irrigation is not all benefits without drawbacks though, so everything must be weighed in together to determine if it is something that would benefit your garden or not.
One of the things that I stress all the time regarding gardening is the health of the soil and the microbiology living within the soil. The healthier and more diverse the ecology within your soil, the healthier and more productive your plants will be. One of the things that the microbiology in your soil need to survive and thrive is water, so we have to keep this in mind when thinking about using drip irrigation systems.
If you look at this photo, a drip irrigation system is being used in a field to put water directly at the base of each plant however all of the soil in between each plant remains bone dry as well as all of the soil between the rows. This does not allow for an abundance of microbial life to survive anywhere in the soil other than directly at the root zone of the plants.
While this does keep weeds from growing, it also retards the natural soil building process from occurring throughout the growing bed, especially in the dry, hot, summer months. The farther apart the drip imitators are on the drip irrigation line, the worse this problem will be.
For those growing in raided beds using the "square foot gardening" method, the drip irrigation lines are closer together because the plants are placed closer together, so it is not an issue as the whole soil is getting wet when irrigating. When gardening in the ground, rows are typically 3 to 4 feet apart from each other, which exacerbates this problem as the moisture never penetrates between the rows.
As you can see in the photo above, the drip irrigation tubing in this grid system is much closer together which will provide a more even distribution of the water over the entire soil surface instead of just at the base of each plant. This allows for all of the plants to be watered at their root zone to conserve water from evaporation while also making sure that all of the soil is getting enough moisture for the microbial life within it to thrive.
Drip irrigation is used to provide deep watering to the plants, which encourages a deeper rooting system. Typically when drip irrigation is used, the system will either be set up on an automatic timer, or be manually turned on and off. Since the water pressure is low and it drips slowly, the systems are normally run for about 2 hours at a time to allow the water to penetrate deep into the soil.
"Soaker hose" type drip tubing is much better for the health of the soil than drip lines which have emitters spaced farther apart like a standard drip tape.
With the soaker hose drip irrigation system, the water weeps through the entire surface of the tubing which allows for a more uniform distribution of the water over the entire soil surface.
I have gardened both with and without drip irrigation systems, and have run several experiments over the years to determine which way is better for the plants, and for the soil. With a traditional drip irrigation system only putting drops of water directly at the base of the plants I was able to see a drastic difference in the microbial life in the soil directly under a drip emitter versus a soil sample taken about 12" away from the plants.
Over a 3 year period I was also able to document a substantial difference in the soil structure between where the drip irrigation system was compared to the soil in between the rows which never got irrigated. I could see a substantial difference between the two. The areas between the rows was a hard-packed clay where the soil underneath the irrigation had been transformed into lose soil. I had placed wood chips on the surface of the pathways to retain moisture from rain, but the water from the irrigation system never reached there. Because the wood chips were on top of the dirt and clay in the pathways, the top 2" of dirt and clay had started to be transformed into good lose soil, but it did not go very deep. The top 2" also had a higher microbial count than the deeper levels had, which made sense when seeing the differences in the soil structure.
Not only do the microbial life in your soil need water to live, but so do the earthworms that are working hard to create good soil structure for you and aerate your soil. Their skin has to stay moist for them to be able to breathe, so if an area is too dry, they will leave it for a moister area. Under the drip irrigation system there were plenty of earthworms, however in the pathway areas with no irrigation, no earthworms could be found at all. Remember, those earthworms are essential, along with the other microbial life for breaking down those wood chips and turning it into rich fertile soil. Without them, it just wasn't happening very fast.
So, after taking everything into consideration from what I have learned and observed over the years concerning drip irrigation systems and building soil quality, I do see times when drip irrigation systems can be beneficial, if they are used properly, but I also see times when they actually do more harm to the health of the soil.
If a drip irrigation system is used where rows of plants are close enough together so that the drip system is irrigating the entire surface of the soil, then I think it can be a benefit. However, if the drip system is spaced too far apart as is typical in an in-ground garden, then it would not be able to provide moisture to keep the microbial live thriving throughout all of the soil so that they can continue to improve the structure of the soil and create a better growing environment for your future gardens.
Now the question comes up. With everything that I have learned about drip irrigation systems over the years, do I use drip irrigation systems now? Yes, and no.
For my raised beds, I use high-intensity growing methods where my plants are planted closer together than you usually would, so I am able to use drip irrigation with the drip lines spaced closer together to make sure that the entire bed is being irrigated. I also use the soaker-hose type irrigation lines.
For in-ground beds, I no longer use drip irrigation systems because it just is not able to adequately irrigate the entire soil surface properly for the best soil health because the irrigation lines are spaced too far apart.
Hopefully, that has given you something to think about regarding drip irrigation systems and you will be able to make a more informed decision on if a drip irrigation system is right for your garden or not.
Until Next Time,
Aloha & 73