18" between rows might be a bit tight, especially since most plants cross into paths by a few inches to a foot...but if you're comfortable with that setup and moving around in it, it can work.

Most keep a minimum of 3ft between rows for easy movement/harvesting and ability to take equipment (harvest storage, wheelbarrows, etc) through the rows.

The type of grass (specifically how thickly/densely the roots thatch) will have a lot to do with how well any lasagne covering method will take care of the grass. Almost all of them will kill the grass, but how thickly the roots hold the soil and each other is a concern for a little while in areas with thickly rooted grass.

Eighteen inches is definitely tight but its what I used this year and will allow me to get an extra row or two in. Trying everything I can to save space :-)

I think I'm going to do the 50' beds lazy lasagna style (did two today-ran out of paper). I'll till up the others and compare/contrast for myself next season.

I'm in the process of making a good amount of lacto bacillus bacteria via the Korean natural farming method. Gonna try spraying that on the lasagna rows and see if it helps.

I'm thinking it would be significantly easier to do a "fake" lasagna bed. Lay out the cardboard/newspaper, wet, 3"-4" layer of shredded leaves or straw and call it good.

Do one proper lasagna bed - as big a one as you have materials for. It's better to dop one bed well than skimpily do a larger space.

Till straw and dry leaves into the rest of the beds and cover them with straw, cardboard and more straw. Check them in early spring and see how it's doing. You may be pleasantly surprised.

My quibble with the paths is that the grass will spread into the beds. Cover the paths with cardboard.

My quibble with 18 inches is that if an adult is kneeling across a path of that width, knees are in one bed and toes in another. (I'm 5'5" and use >24 inches when kneeling with my toes pointed to the rear.)

If you kneel slantwise to stay out of the beds, you strain your back bending funny to reach the middle of the bed.

Don't set dimensions on paper. Use your body as the standard of measure.

Measure your reach: reach x 2 = maximum bed width (probably about 4 feet)
Measure the distance from toe-tip to front of knee when you are kneeling = minimum path width.

I think Mel Bartholmew set the size of the square foot beds at 4 feet because he found that was the widest bed one could comfortably reach the center of. Many years ago, BMB (Before Mel Batholomew) I made planting beds 6 feet wide because I had no problem, then reaching 3 feet into the beds. Today that is not very comfortable to do and the beds have been reduced to 4 feet wide.
Paths between beds are also 4 feet wide since that is the space I need to work in the beds without going into the beds. The paths are grass and there has not been a problem with that grass growing into the planting beds because barriers to keep the grass out were installed.

1. Paths between rows are obligatory. The reason is to avoid compaction by never stepping on the soil, and this means NEVER. Compaction is the enemy of fertility because it robs you of the use of the fertility and moisture below, say, 15 inches depth.

2. The far-and-away best soil amendment is compost; 1/2 inch every year, and twice that to start with. Shredded leaves are fine, but they take 90 days of non-freezing weather to decompose. This is ok for late crops such as tomatoes, squash, and eggplant, but useless for early crops like lettuce, spinach, and radish. Rye (or barley and wheat) are fine (too late for any other cover crop) because it will decay in 30 non-freezing days after incorporation.

3. I would take a simple soil test this time next year to see which minerals might be deficient or in excess. Not really a priority until the soil has some tilth.

Regards, and good luck, Peter.

heavy clay needs manure especially if you're growing crops for farmer's market when you want consistent growth for consistent harvest

it's going to take more than a few leaves to build the tilth you want for good garden results

We have glatial till with little topsoil in the area of our vegetable garden along the driveway. Lots of manures plus bedding mulches of straw & shredded leaves plus wood chips between beds. Now spots can be dug by hand. It took a lot of work to get it that way, but the past few years we made the best progress because we stopped turning soil over with a hand fork in the spring.

If planting seeds you can always prepare a seedbed with some sifted compost.

hope that helps

I agree that plenty of well rotted or composted manure that has lots of hay and straw is about the best way to build up organic matter with some nutrients. Also leaf compost can be good . Some organic fertilizer is good too. Remember that you are removing nutrients yearly so there has to be put back. Fall and winter cover crops can add organic matter and if these are deep rooted, they can bring up nutrients and open up the subsoil for better root penetration and better drainage.

I use 18 inch paths to maximize growing space and yes, I run a wheelbarrow easily down these paths. I just lightly till these to keep out grass and weeds. For the most part I have such nice and loose soil that I have wider unbordered beds and I am not afraid to walk some on these. Your mileage may differ according to your soil, but I don't see how... much.