By Jim Lakin, MD
One sure sign of spring for me as a young man was my father-in-law rototilling his vegetable garden. He’d fire up his trusty TroyBuilt and belching smoke and fumes, pulverize a good portion of his back yard. The resultant fluffy black soil seemed to invite planting.
Thinking has changed over the years, however. Many soil scientists are questioning the wisdom of unbridled tilling. We’ve come to realize that garden soil is more than a receptacle for water and plant nutrients. Rather it is a living entity harboring billions of microbes and minerals most of which are highly beneficial to plant growth. It also is a complex structural milieux, permitting the passage and retention of water, the movement of oxygen and other gases of plant metabolism. Tilling can disrupt these structures and destroy many of the microbes beneficial to plant growth. Over time this can lead to soil compaction, reduced water holding capacity and erosion. Paradoxically, it also can bring weed seeds to the surface to germinate. That’s not to say that the time-honored process of tillage is without benefit. It does create an even seedbed. It warms the soil in spring and helps to work in compost and other soil amendments. So how can you achieve these desirable results from methods other than tillage?
In starting a new garden, a rototiller will make quick work of existing vegetation. However, the same result can be obtained by solarization or occultation. Solarization is achieved by placing a sheet of clear plastic over the future garden area and letting the sun fry any plants underneath. I prefer occultation, a fancy term for smothering plant life under black plastic.
If you are trying to start a garden on heavily compacted soil, say an area that’s been run over by heavy mower for years, tilling may be the best solution. However, if the soil is workable consider using a broadfork. This is a dandy tool to reduce compaction in a new or existing garden without breaking up the soil aggregates. A broadfork has several metal tines on a bar with a couple of handlebars on each end. Stand on the bar and use your body weight to plunge the tines into the soil. Lean back and pull the tines through the soil. The creates soil aeration without turning it over or breaking it up as a tiller would.
Weed management has been a traditional role for tillers. The problem is they bring weed seeds up from the ground as they turn in grown weeds and their seeds. The end result is more annual weeds over time. If you reduce tillage this favors the dominance of perennial weeds which can be hand pulled or reduced by solarization or occultation as we talked about.
Working in amendments of compost, manure, commercial fertilizers or cover crops is an important process to replenish your garden soil’s fertility. Traditionally this had been done with a tiller although there are good alternatives. We’ve already talked about the broadfork. Alternately a tilther can be used. This is a modified light tiller that only tills the top two or so inches of the soil. Being much shallower than the traditional tiller it can work in amendments while being much less destructive of the deeper soil structure.
Want to learn more? Check out these links to the University of Minnesota Extension.