Posted By: Wesley Chun, Ph.D. /
A commercial macadamia nut grower recently asked for help starting an organic orchard on recently acquired land. Once part of a large macadamia plantation, the land has lain fallow for multiple years. This would be a challenge for the grower and I since neither of us had operated an organic tree farm. However, it was an opportunity to evaluate organic products from day one and I could not say no. After all, there is a first time for everything.
We first added composted macadamia nut shells to improve the organic component of the soil. At planting, soft rock phosphate and Azomite® were added to each planting hole. After planting, Grower’s Secret Nitrogen (GSN) and Soluble Seaweed (SS) were added through the drip lines and the rate will be gradually increased over the next three years. Gypsum did not arrive in time for planting so it will be top-dressed at a later date.
The logic behind these amendments is straightforward. Macadamia nut shells typically have a C:N ratio of 40:1. If composted with poultry or steer manure, ratios of 14:1 are possible. Addition of high C:N ratio materials stimulate microbial activity, essential for a healthy soil. Soft rock phosphate promotes root growth, which is very important for newly planted seedlings. Azomite contributes silica and several important mineral nutrients. Nitrogen and potassium needs of the plant are addressed with GSN and SS, respectively. Plant performance will guide our fertilizer modifications via the drip lines or by foliar application. Lastly, gypsum is our main organic input for calcium. Thus, we will have organically addressed all the nutritional needs for growing organic citrus.
We are confident that we can be successful in producing organic citrus. Our plan is to increase the amount of nitrogen and potassium through the first three years of growth, and annually top-dress with phosphate and gypsum. After year three, our plant fertilization program will target replacing nutrients that are removed with each harvest. We will also try a few tricks with our growth enhancer (Grower’s Secret Professional), our Soluble Seaweed, and potassium to increase yields and improve quality.
We have identified several organic materials to address potential insect, bacteria, and fungus problems, which are possibly in our future. Culled fruit could even be used to produce a natural herbicide and insecticide for the orchard. Stay tuned to see what happens.