Applying fertilizer in the same operation as planting has become the most common approach to supplying crop nutrients. It requires the selection of equipment that can carry, meter, and distribute the fertilizer product to the ground openers. Whether single or double shooting, an appropriate opener is required to place the fertilizer, while at the same time and virtually in the same location, place the seed and to ensure there is no compromise to the quality of the seed bed and placement of the seed; in many soil conditions, not an easy task. Considerable investigation by the farmer is needed before selecting an opener to fit a particular farm. The results the opener achieves must be continually monitored during planting to ensure proper placement and separation of the seed and fertilizer.
Air seeders in the 70’s and early air drills used an air flow system to distribute seed and fertilizer to the ground opener. The seed and fertilizer placement is similar to that used for decades by grain drills, except that sweeps on air seeders use almost all of the possible seed bed. Now, with modern air drills this method is called single shooting. Essentially, the seed and fertilizer is all placed in the same general area or zone and in close proximity to each other.
Advantages of single shooting:
A lower cost system of equipment.
Provides a solid base of soil in the seed bed for seed placement
Depth of seed placement and soil cover is easier to control.
Lower tractor power requirement.
Places the fertilizer close to the seed for early uptake.
Disadvantages of single shooting:
The quantity of nitrogen in the fertilizer and, in fact, the total amount of fertilizer product, may exceed the amount the germinating seed and emerging plant can tolerate.
Only uses dry granular fertilizer that can be carried in the air system.
For years banding was the only way to apply anhydrous ammonia. Deep banding followed where all the crop nutrients were placed together in a single band by an operation in the fall or before planting in the spring. Innovative farmers and manufacturers then combined the seeding and fertilizing systems onto one machine and called it double shooting. The first systems were simply a single shoot air seeding system, with a liquid fertilizer or anhydrous ammonia system added to it. That was soon followed by twin tank air flow and meter systems to handle both seed and granular (dry) fertilizer. The ground openers to handle the two products were designed to keep the seed and fertilizer in individual bands or rows and separated by a buffer of soil. The goal in double shooting, whether through a single opener or a combination of openers, is a seed row or pair of seed rows with a fertilizer band placed beside it and at the same depth or slightly deeper.
Advantages of double shooting:
Flexible fertilizer application rates between what is seed placed and what is side-banded.
Keeps the hotter fertilizer band away from the germinating seed.
One pass through the field plants and fertilizes.
Any type or combination of fertilizer types can be used.<
Anhydrous ammonia can be used with planting. It is less expensive and increases field efficiency of the planter.
Double shooting combines an opener and a packer wheel that opens and closes the furrow quickly to preserve soil moisture. The shape of the seed row made by the opener must match the packer wheel to ensure all the seed is firmed into moist soil.
Disadvantages of double shooting:
Many double shoot openers do not work effectively in variable soil conditions.
Systems likely to cost more.
Some double shoot openers consume more draft so require more tractor horsepower. Higher draft machines require a tractor with considerable weight to provide the needed pull and low wheel slippage, and then very large tires to reduce soil compaction . If the fertilizer banding point fractures the soil below the seed, then poor moisture transfer results. At its worst, the fracturing creates a lumpy seed bed which cannot be properly packed, reducing plant population. As noted in the photo, variable and lumpy conditions may allow a wide dispersion of the seed row.
Double Shooting (of fertilizer) Through a Separate Opener
Separate openers for seed and for fertilizer, one trailing the other, have been available for quite a while. They offer more assurance that there is a soil buffer between the bands of seed and fertilizer and particularly where soil does not flow well. The trailing opener plows a new furrow and positively closes the furrow from the front running opener.
The mid-row bander system is another form of double shooting. This system provides a fertilizer band that supplies two seed rows with nutrients. Not having to deal with an additional band for fertilizer, the focus of the seed opener can be quality of the seed bed. It also provides flexibility in the selection of the seed opener or even to change the seed opener shape or type during the season depending on the crop type or other factors.
Separate Seeding and Fertilizing Operations
If a perfect match of seeding and fertilizing systems and ground opener can’t be achieved, it is better to apply the additional nitrogen fertilizer in a fall or early spring operation. This will ensure the seed bed is NOT COMPROMISED while planting or that a damaging amount of fertilizer is not placed with the seed.
-Select fertilizer banding equipment for the lowest possible soil disturbance and minimum loss of standing stubble. Exceptions to this might occur where excess spring moisture is consistently a problem.
-In dry areas, caution is needed in disturbing the soil surface before planting in the spring. Opening the soil surface will always increase soil moisture loss, so minimum soil disturbance and a packer over the fertilizer furrow is essential.
Other options are available for post-planting fertilizer banding or post-emergence application.