April 2003

Transporting outdoor-grown potted crops By Mike Porter

This article will focus on a system that can achieve significant cost savings for outdoor nursery stock. The system is designed to facilitate the transport, placing and spacing of nursery stock and is suitable for pots ranging in size from 1-5 gal. Handling pots this size is obviously hard work, and the risk of injury and the resultant workers’ compensation claims make such handling an ideal candidate for some sort of automation.

Previous articles have focused primarily on automation applications for greenhouse growing. There are, however, products available that work very well for outdoor growing. This article will focus on a system that can achieve significant cost savings for outdoor nursery stock. The system is designed to facilitate the transport, placing and spacing of nursery stock and is suitable for pots ranging in size from 1-5 gal. Handling pots this size is obviously hard work, and the risk of injury and the resultant workers’ compensation claims make such handling an ideal candidate for some sort of automation.

The system is conceptually similar to that described in a previous article dealing with handling pot crops grown on the floor of a greenhouse. (See the April 2002 issue of GPN) The equipment used, however, is designed specifically for outdoor applications. Such systems have been around for a few years but required ground that was very flat, a condition not met by many operations. The latest generation of products still requires fairly level ground but is able to work in a wider range of terrain. Growing on ground cloth is ideal but not necessary.

The system consists of three primary elements: traditional transport trailers specifically sized for this application, a station consisting of a conveyor and a robot that can load the trailers, and a specialized forklift to place and space the pots. While the maximum benefits are achieved when the entire system is employed, the individual elements can stand on their own.

Process

The first step in implementing a system is to provide a lean-to structure outside the headhouse to provide cover for the trailer loading operation. The lean-to can be a very simple structure, since its only purpose is protection from precipitation. A feed conveyor will come from inside the building to stage pots for the trailer-loading robot. This conveyor can be supplied automatically from potting equipment or fed manually. The conveyor will leave the building at a height sufficient to clear the empty trailers. Linked with the conveyor is a robot that will push a row of pots onto a trailer underneath the conveyor. The robot will sense when the conveyor is full and when there is a trailer in position.

The trailers are advanced automatically to accept each new row of pots. This is accomplished by a set of rollers that are electronically linked to the rest of the system. When a row of pots has been loaded on to the trailer, the rollers are activated to advance the trailer to accept the next row. The only manpower necessary is to ensure that trailers are available.

The trailers must be sized to be the same width as the forks that will be described, which will also match the pushover robot. An alternative is to push the pots onto a tabletop, which is then staged on a simple system such as a set of pipe rails. These tabletops can then be pushed onto a transport trailer. Such a system can reduce the number of transport trailers and tractors necessary, while still allowing the robot to run at peak efficiency.

The centerpiece of the handling system is the forklift itself. Current systems consist of a standard outdoor forklift specially fitted for this application. A separate set of controls is mounted on the forklift, or in some cases on the forks, which will control the movement of the truck during placing and spacing. A set of special forks is required for each size pot to be handled. The forklift will remove pots from the transport trailer and place them on the ground. The placing is done in a continuous motion. Because of the computer controls, when the placing action is initiated, the operator’s only function is to keep the truck in a straight line. The actual placing cycle is approximately 10 seconds. The normal fork would be 8-10 feet wide and 5 feet deep. Many pots can be placed in a short period of time. The forks can also be used to space the crop when necessary. All of that is necessary is a separate program in the control system.

One of the great advantages of the current system is that the trucks are standard and can be fitted with regular forks to do other work when not needed for placing and spacing.

Other uses

Another possible use of the elements of such a system is to aid in the shipping process. The normal method is to send people into the beds with some type of transport cart to select individual orders. This process is obviously time consuming and inefficient, especially in a nursery of several hundred acres. In my view, the driving force behind this method is that, due to the unwieldy nature of the crop, the fewer times it is moved the better. With a more automated material handling system in place, the whole picking and shipping process can be revaluated. The specialty forklifts can remove plants from the beds as easily as they can place them. This opens up the possibility of utilizing a staging area close to the shipping area. This staging area would house a variety of plant material, certainly the most popular varieties. Most picking for customer orders would be done from the staging area. The staging area would then be replenished when product is sold. The replenishment would be done in quantities, which maximizes the efficiency of the forklifts. The cost of operating the forklift is minimal compared to the labor that could be saved over the present picking methods.

Costs

The costs of a system are very reasonable for many nursery operations. The cost of the forklift itself is $50,000-60,000 including the controls. Since the truck can be used in other applications, the $15,000-20,000 of the controls is the only relevant cost. The standard trucks used can easily be maintained at dealers in most parts of the country. Each set of forks will cost approximately $12,000. For most growers doing 1-, 2- and 5-gal. pots, the cost would be $36,000. The pushover robot system including conveyors and rollers for indexing the trailers would be $65,000-70,000.

As you’ve heard from me before, the more you use automation, the shorter the payback period. Using the above system to help with shipping as well as placing is an example of how to leverage your investment in automation.