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Growers Talk Production: Theory of Constraints
| Roger McGaughey
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>> Published Date: 7/15/2008
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I enjoy reading books, but with my grower schedule there isn’t a lot of time for such pleasant things. However, before I went on vacation in February, Michael (my boss) gave me an interesting audiobook, The Goal, by Eliyahu M. Goldratt and Jeff Cox, to listen to while I was on the long plane rides to and from our holiday destination.
I didn’t finish it on my trip, but later, on my return, I listened to it while traveling to and from work. The story is about the trials and tribulations of a plant manager trying to improve production in his operation. The greenhouse business is a manufacturing industry after all, and a lot of his statements and comments pertain to our business. He uses words and phrases like throughput, bottlenecks, weakest links, common sense, thinking processes and constraints.
At Michael’s Greenhouses we’ve used a lot of these principles in reassessing our planting processes, and output has certainly increased with improved efficiency. We’ve been on top of our planting requirements on a weekly basis all through this spring.
Coincidentally, these same principles were relevant to another major improvement we made this season in a 3⁄4-acre double-poly house. We normally grow two layers of hanging baskets with drip irrigation on a timer system. Last year, we hung extra baskets on hooks from the second layer, creating a third layer to increase capacity, but we had to hand water every basket with a system that already had pressure limitations. Ron, our new production manager, and I talked about how to improve the water pressure and make these lines a permanent fixture without being so labor intensive.
This leads to my interest in The Theory of Constraints (T.O.C.), as outlined in The Goal. “Making progress is a process of ongoing improvement. A process is a sequence of steps to be followed and throughput is the most important aspect.” Of the five steps outlined in T.O.C., I want to highlight the first two. Step 1 is to identify the main source of the constraint, and Step 2 is to decide on how to exploit the constraint (bottleneck).
Our constraint was the amount of water being supplied to any given point of the greenhouse. To cut a long story short, Ron designed and built a new system using larger header pipes and valves. Water compensators in the lines evened out the flow. The header pipes also retained less water than before, so less fertilizer was tied up in the system. We’ve now added two more irrigation lines for hanging baskets per bay, which amounts to 4 x 63 x 8 = 2016 more drips in the house. This is a significant increase in throughput per crop turn in the one house. Basket watering on our timer system is now a simple operation of opening valves, selecting the appropriate fertilizer from a Dosatron, and letting the timer complete the exercise more quickly than before. Attaching 3⁄4-in. (instead of 5⁄8-in.) hose pipes without shutoffs to my double nozzles, as I do on the rest of the nursery, means I can use two double nozzles at any valve. This is a major improvement in hand watering efficiency for crops on the floor. With oil prices going up, these extra baskets help spread the heating cost per square foot and create very welcome extra revenue. Fortunately, this permanent third layer doesn’t seem to adversely affect the crops on the floor underneath.
Our improvements were made in the downtime in January, and it’s interesting that our thought process and actions were parallel to the ideas outlined in The Goal. The book has a lot of relevancy to our industry, and I’d highly recommend it as thought-provoking reading material. You can learn about the other three steps in the theory of constraints, and I’m sure anyone who reads The Goal and who’s prepared to make some changes can gain significant improvements.
First you need to decide what you want to change, then what to change it to, and lastly how to effect the change. A little common sense and a lot of thought can lead to very positive results.
Roger McGaughey, head grower at Michael’s Greenhouses in Cheshire, Connecticut, was educated in Northern Ireland and England and has 34 years experience as a grower.
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