Of all the cultural practices required to care for the Christmas trees at Shady Pond, providing for their nutritional needs is the most technically complex.
Not a single ounce of fertilizer is applied without first knowing what is currently in place. To do so would create imbalances that are potentially damaging and can be very difficult to correct.
The process begins months in advance of actually applying the custom mixed fertilizer. Soil samples are collected in late December. Although the sampling pattern is somewhat random, care is taken to include those areas of each field that are known to be at the extremes of performance; the very best and the very worst. The samples are about an inch in diameter and about 4-inches long. A dozen, or so, plugs are collected in each field and placed in a bucket use only for that purpose to avoid any possibility of contamination. The contents of the bucket is then mixed to blend the soil into a composite sample that represents the nutrient condition of the entire field.
The composite sample is then transferred to a special bag made of inert materials that will not alter the soil nutrient assay. It is then shipped to one of the world's most sophisticated agronomic laboratories in Memphis, Tennessee. A&L Laboratories analyses the samples to determine their existing nutrient content in the three basic categories; nitrogen, potassium, and phosphorous. The soil is also analysed for micro-nutrients including sulphur, iron, aluminum, manganese, magnesium, and boron. Boron and sulphur are consumed by the trees and are consistently deficient. As a measure of the precision of this process, note that concentrations of boron below 1/2 part per million (ppm) are deficient but above 1-ppm they are toxic.
Many laboratories can determine the nutrient content of soil but A&L Laboratories' true expertise is in formulating nutrient recommendations for the trees grown here at Shady Pond. They seem to always craft just the right menu.
Once the analytical work and recommendations are completed at A&L, they transmit the test results by e-mail as .pdf files.
Using A&L's recommendations as a basis, the final fertilizer mix of commercially available materials is determined, and fine tuned, here at Shady Pond. The recipe includes amounts by weight (pounds) of ingredients like urea, ammonium nitrate, ammonium sulfate, diammonium phosphate, potassium, and elemental boron. Each field has its own unique mix. This is definitely NOT 'one size fits all'.
The recipes are then sent to Shady Pond's fertilizer supplier to verify current availability. Circle 'T' Farm Supply reviews the mix specifications and advises us of the various fertilizer components in their stock that come closest to our needs. Final adjustments are then made to the mix for each field.
Granular fertilizer material is stored in the cubicles at Circle 'T' in the building seen in the photo to the left. Since most fertilizer is deliquescent, this open arrangement promotes natural drying and reduces the sludge like material that often forms on concrete floors in closed storage areas.
Using the final specifications, the folks at Circle 'T' build the mix. The wheel loader operator is in total control of the project. He scoops bucket loads of each component from the appropriate cubicle and very carefully dumps the material into the weigh hopper while observing the amount added on the scale display. Once the specified quantity is added, the amount remaining in the loader bucket is returned to its cubicle. This process is repeated until all the ingredients are in the weigh hopper. Small quantity micro-nutrients are precision weighed on a platform scale in a separate building and added to the weigh hopper by hand.
The still somewhat segregated mass of granular material is then moved to the mixer using the transfer conveyor. The mixer rotates like a cement mixer blending the material uniformly. The mixing operation is relatively brief.
With mixing complete, the material is transferred by the belt conveyor to the transport vehicle. At Circle 'T', transport vehicles include trucks, buggies, and tenders. Trucks and buggies (trailer) are typically capable of directly spreading the fertilizer in open areas and are of no use at Shady Pond. So we transport the fertilizer in tenders. Tenders are self-contained fertilizer handling units including an engine, hydraulic system, hopper, and screw conveyor all mounted on a trailer chassis.
The fertilizer tender is seen in the photo below. The long cylindrical component at the rear of the unit contains a conveying screw. The screw consists of a center shaft with a helical flight mounted on it. The flow of granular material in to the screw conveyor is controlled by a manual gate in the bottom of the hopper. With the screw conveyor discharge point being as high as it is (11-feet), the auger sock is needed to guide the material into the spreader hopper.
The spreader in the photographs is referred to as a cyclone spreader. In its simplest form, it is intended to distribute granular material in wide swaths of about 30-feet. To accomplish this, the spreader is fitted with a spinning disk that includes straight impeller blades. The granular material falls through a control gate in the hopper bottom and onto the spinning disk. The impeller blades accelerate the individual granules through centrifugal force causing them to remain airborne over a large distance behind and to either side of the spreader. To use the spreader in this configuration at Shady Pond would largely defeat our purpose by fertilizing grass and not trees.
To ensure that the trees receive the most benefit from the fertilizer, the cyclone spreader is modified with a shroud that surrounds the disk and impeller blades. The shape of the shroud is quite similar to the housing found on squirrel cage and paddle wheel blowers. It includes a tangential discharge chute that places the fertilizer directly under the trees. The shroud is referred to as a 'side row attachment' or 'banding attachment'. In truth, the banding attachment discharges not only granular fertilizer but high velocity air as well. And the air stream aids in transporting the fertilizer to its final destination.
Using the Adams Fertilizer Equipment tender, the cyclone spreader can be reloaded in about 30-seconds. And about 5,000-pounds of material can be applied in a single day. This is enough fertilizer to feed 10,000 to 12,000-Christmas trees for a year.
Clearly, the most important aspect of applying fertilizer to the trees at Shady Pond is the calibration of the spreader. Too much fertilizer will damage, or even kill the plants; too little will not produce the intended effect. To set the flow rate of the cyclone spreader, the fertilizer is discharged in to a bucket for 125-seconds and the bucket is then weighed. The open space in the control gate is adjusted to produce the calculated flow rate. The time of 125-seconds is the time required for the John Deere 5320N to traverse a 700-foot long row in gear B-3 at 1700-ERPM (engine revolutions per minute).
The prudent use of fertilizer is well known. Even Native American culture included the use of fish fertilizer to maximize crop production in the late 1400's. Fertilizer not only enhances growth but it also improves the general health of the plant making it possible for them to withstand the attacks of insects and pathogens using their natural defenses. As with we humans, a balanced diet goes a long way to ensuring good health.
We are what we eat.