In addition to the reasons farmers till you listed they till for weed control. Here in this part of Nebraska there is a lot of no till farming. Round-up ready crops are planted and round up is used instead of cultivation to control weeds. It is more cost effective than going over a field multiple times to cultivate or spray for weed control.

In my garden I till up in the spring because there is a lot of clay and the ground packs down hard as concrete! The soil does need some aeration. I am in the process of trying to add more compost each year to keep it from being too heavy. In the farm fields the natural decay of the corn stalks and soybean plants left after harvest do that job. Not so much going on like that in the garden as I try to remove all the dead tomato plants etc. to prevent disease.

It would seem that with weed control and good aeration you could avoid a lot of tilling. I have cut back on my tilling to where I till in the mulch after I take out the tomatoes and then a once over in the spring to loosen up the soil that has been packed down over winter.

Tilling is not going to destroy the beneficial micro organism. becaus they will be there no matter what.
Small farmers and gardener alway hoe around their crop. This is partly because for weed control and also for airating and better water absorbtion.

Tilling has alot of advantages. As our bones benefit from sun, affects our mood, plants need it, so does the soil. Sunshine affects the chemistry of soil.
Another benefit of tilling is AIRATING the soil. This should actually help micro organism. It is posible for nitrogen from air be absobed when the soil is loose/airated and gets sunshine. In the old world farmers planted wheat one year and let the soil rest another year. Durin that time they plowed the land couple of times and in the fall planted wheat. It has been shown that if you take one parcel of land and plow onehalf of it in the summer and leave the other half untilled and plant wheat on both in the coming fall, you will see that the part that had been plowed will have a higher yield.
Yet another advantage of tilling/turning over is that some of the nutrient sink down and turning over the nutrients will blended in again.
In some climats tilling might be difficult becaus of too much rain. So then they go ahed and plant without tilling/ plowing/turning over as there is a time constraint.

I agree with cyrus that some tilling has a definite place in the home garden. No-till may work great for the commercial planter/farmer and from what I read it is definitely the trend nowdays.

But limited tilling for grub, pest, and weed control benefits are big selling points for me and have been for years. I'm not advocating the Mantis ads type of daily tilling just because you can - that is done for appearance only and for lazy man weeding - but a good spring or fall tilling of the garden has a role.

Plus we plant green manure crops and cover crops in the winter and to benefit from them they need to be tilled in in the spring.

As to why farmers till? In part for the same reasons I do - soil pest and weed control. Plus if they have especially heavy soil tilling makes mechanical planting much easier and can improve soil drainage. I don't agree that it depletes nutrients (it isn't the Grapes of Wrath dust bowl) nor does it kill off the beneficial organisms - disturbs yes, but destroys, no.

But there is much debate on till vs. no-till and literally hundreds of discussions about it scattered over many of the forums here at GW - especially over in the Soil & Compost forum. A search will pull them up for you if you want to read through them.

Dave

g'day,

what farmers do is not necessarily best practise and sustainable they do lose a lot of moisture at till time and soils structure is damaged for no good purpose. and their tilling can allow errosion by wind and water, seen it many times.

as for home gardeners what the farmer does has not a lot of bearing as most of us want to grow naturally without the aid of chemical applications, plus we find that there is no need for that extra manual work of tilling.

take a look at how we do our raised beds no digging ever, no weeds and water wise gardens, that produce from day one.

len

Here is a link that might be useful: lens garden page

Some organic and semi-organic farmers use tilling to enrich the soil. In the fall they plant a cover crop of rye seed. When the rye starts to grow the following spring they will plow the organic material back into the soil, a "green" manure as it is called. This is also done with clover, alfalfa, and wheat.

Tilling makes the soil more workable. For those of us that don't plant in raised beds, it loosens the top 8" or so of the soil and makes it "loose". This helps plant roots develop faster, it helps moisture get into the ground during the spring rains, and it helps with mixing in composted material and incorporating it into the soil.

In the fall, I rake all of my leaves onto a large tarp and drag them to the center of my garden plots. I leave them there all winter long. In the spring, I mow them over with my push mower a few times and then spread them out with my rake. When it is time to till, all of this organic material is incorporated into the ground.

Wow-i thought this would be a hot topic. Probably would be/has been on the soil and compost forum as Dave already noted.

Well, i don't know about farmers but i can tell you why i till.

*to loosen the hard packed clay
*to elimate the existing vegetation (weeds!)
*to incorporate lime, phosphorus, and calcium into the root zone (phosphorus does not move well in the soil and needs to be placed at the root zone. i assume lime works better when it is evenly distributed throughout the upper 6-12")

After the initial tilling i pile on as much OM as i can lay my hands on in the form of mulch. OM gets well distributed through the soil by helpful organisms. i try not to till again unless it becomes necessary although i may need to modify this approach as i try my hand at traditional vegetable gardening this year.

This approach has worked really well for me with my soil in my growing conditions. YMMV.

Tilling is useful to work in organic material and soil amendments. It loosens compacted soil, uproots weeds, and turns up insects pests and weed seeds where they can be dealt with by nature or by the gardener.

No-till culture requires working the ground with hand tools, deep, permanent mulch, or the use of herbicides to kill weeds without uprooting them. Each of these presents its specific set of problems.

Its possible to over-do anything. Inappropriate tilling for your particular soil and conditions can create problems. So can not tilling at all.

I don't have a tiller and desperately wish I did because my sandy soil requires far more organic material than I can readily have worked in by a teenage son with a digging fork.