Orchard Watered with Greywater and Fertilizer Injector

Q. First off I want to thank you for the inspiration and motivation to get my backyard orchard project off of the ground. I planted 22 bareroot fruit trees this winter, 20 of which have budded out! I am still hopeful on the remaining 2.

            I have also installed a greywater drip irrigation system using the water from my laundry, the system I am using waters the whole 20'x30' orchard area rather than each individual tree. What I am curious about now is if I should utilize the surge tank in my system to apply any fertilizers or possibly something to combat the alkalinity of our native soil? I am noticing chlorosis (yellowing) already on the new trees this spring. Do I need to worry about that now?

A. Congratulations on your mini Orchard. Be careful with the type of laundry detergent that you are using in combination with your greywater system. Make sure it is biodegradable and plant friendly.

            You might want to do some checking on the state regulations on the use of greywater for irrigation. This would be overseen by the Nevada Division of Environmental Protection and much of that information should be online or a quick phone call away.
Nevada Division of Environmental Protection Website

            Using a fertilizer injection system is very convenient and adequate as long as your irrigation system is designed and installed well. If your irrigation system applies water evenly, then the fertilizer will be applied evenly as well. Make sure you incorporate a 150 mesh screen filter somewhere at the front of the system.

Mesh filter for drip irrigation paired with
pressure regulator

            The advantage of fertilizer injection systems are that they can apply small amounts of fertilizer continuously through the growing season (through most of August). It sounds like a fertilizer injector would apply more fertilizer than applying fertilizer by hand once in the spring but this is not necessarily so.

            Applying small amounts of fertilizer on a regular basis is much more efficient and can lead to significantly less fertilizer applied if you manage the irrigation system and very small amounts of fertilizer applied closely.

            You do not need to inject anything to combat alkalinity of the soil. Select acid forming fertilizers and use organic mulches. If you use organic mulch on the soil surface it will do a lot to improve the soil and combat alkalinity.

One brand of iron chelate EDDHA

            You could inject an iron chelate into your irrigation system to combat yellowing due to chlorosis provided the water is below a pH of 7.5. If you cannot guarantee this pH in your water then use the iron chelate EDDHA which is stable through the alkaline pH range. The other sources of iron fertilizers  are not stable under alkaline conditions and will drop their iron once they are put into water with a high pH.

            If you decide to inject fertilizers into your irrigation system then start the injection cycle after the water has been delivered to the plants for a few minutes. Water is not delivered evenly during the first few minutes of the drip irrigation cycle. Once the drip system is fully pressurized, well-designed drip systems then apply water evenly.

            Stop injecting fertilizer several minutes before the irrigation system shuts down. Several minutes of uninjected water will clean out the irrigation system of fertilizer that might be stuck in the irrigation lines.

            Water that remains in your irrigation system containing fertilizer will lead to the growth of algae and bacteria in your irrigation lines. Algae and bacteria are major culprits in plugging your irrigation system if you are using drip or even sprinklers.