Richard L. Parish
The use of plastic mulch is an important cultural practice inthe commercial production of fruits and vegetables, but removal and disposal of the mulch cause problems. Commercial machines are available to lift and loosen the mulch, but many growers collect the mulch by hand. Commercial machines are available to collect the loosened mulch, but control of spool speed is a problem. The difficulty with mechanizing the collection of the mulch is the need to vary the speed of the spool on the collector to compensate for the increasing spool diameter as the mulch builds up on the spool. A simple, automated mulch collector has been constructed at the Hammond Research Station.
To simplify building and testing a prototype, the lifting/loosening operation was done by a separate machine similar to the available commercial machines (Figure 1). The prototype mulch collector is shown in Figure 2. The spool was driven by a hydraulic motor connected to the tractor remote hydraulics. An adjustable flow control valve was installed in the line to the motor.The motor was mounted on a swing arm suspended from a bearing on the spool shaft. Travel of the swing arm was damped and limited by a pressurized hydraulic shock absorber. The swing arm was mechanically linked to the flow control valve so that the flow control valve, and thus the spool speed, was adjusted as the motor/swing arm assembly rotated in response to changes in load (torque) on the spool. It was possible to automatically reduce hydraulic flow (and thus motor speed) to zero. This allowed the tractor to be stopped completely without disengaging the hydraulic lever, making control of spool speed fully automatic.
The spool was designed to allow easy removal of the rolled-up mulch material. Two alternate spool systems have been used successfully. Two wood 2-by-4s were grooved so that they would form a square box over the spool shaft. Plastic mulch was wrapped onto the 2-by-4s, and then the 2-by-4s were removed and discarded with the plastic mulch. The machine was later modified to use fiber spools (the cylinders on which the plastic mulch was originally wrapped when purchased) to replace the 2-by-4s. The fiber spools were then discarded with the plastic.
The prototype was used to remove plastic mulch from a bellpepper crop. The prototype mulch collector worked as anticipated.The swing-arm mechanism effectively sensed torque on the collection spool and adjusted spool speed accordingly. The prototype effectively maintained operation when the tractor was slowed down, stopped and started. Once adjusted, operation was automatic. In addition to a tractor driver, one person was needed to tie the plastic mulch to the spool at the beginning of each row and whenever the mulch tore.
Observations on use of the prototype on several small research fields revealed that a crew of two could do in two hours,with less effort, the work that a crew of four to six had previously required three to four hours of hard labor to complete.
Richard L. Parish, Professor, Hammond Research Station, Hammond, La.
(This article was published in the winter 2000 issue of Louisiana Agriculture.)