Organic Farmer Network: Network Discussion Summary

Topic: Plastic Mulch

Ken: “We use a lot of plastic mulch and it is pretty effective, we grow good crops on it. For many of them, we mulch the row middles between the plastic with straw and if we get enough down that is good control and has a lot of benefits, including making a nice place to crawl along harvesting stuff. Still there are always enough weeds that get thru to make some seed and one smartweed or pigweed that goes to seed results in a million seedlings the next year spread over a big area. Crops like flowers , we don't usually mulch the space between the plastic, using the weed eater to keep them down. Crops like tuberoses, I tried on plastic, but given the close spacing ( lot of holes in the plastic) and slow growth, we wound up with way too much crab grass coming thru the holes that had to be hand weeded. Last year we went to a 2 row cultivator for the tuberoses and it was less work than growing them on plastic, a lot easier to plant. Crab grass is still a major menace there. I am cultivating potatoes with the 2 row and right now after 3 trips over, and 1 hoeing, they are very clean, but the crab grass is just starting to germinate here and will likely come up thick after the taters are "laid by." I could go to the 2 row cultivator for a lot of crops, but that puts small things on a wider spacing ( 32 inches) and is a lot of bare soil and not an efficient use of space and water. Crops like lettuce are great on plastic- it grows fast enough to shade the weeds in the holes out, but then it does that pretty well on bare ground too. The last 2 years that I grew an acre of lettuce for Whole Foods, I laid plastic in the fall, and we could plant when we wanted in March without regard to wet soil, and grew great, clean (no dirt), weed free lettuce. We have planted over wintering flowers on plastic with good results, some hand weeding of chick weed coming thru the plastic, but last fall was too wet to lay plastic, and we have spent way too much time getting chick weed and hen bit out of them this spring. Could not lay any plastic this spring either until in time for first tomatoes and squash so everything planted in March/ early April is on bare ground. We are doing a lot of wheel hoeing and hand weeding.
I haven't done any mulching directly around plants for a good many years. Seems awfully labor expensive and material costly, yet it does have obvious benefits. I like using plastic, it is a great production tool, yet has some obvious negative aspects, disposal being a big one. We have cut back from 4 acres of plastic a couple years ago, to about 2 this year.” click here for details about video featuring Ken’s plastic mulch system

Nicholas: “I am using plastic on strawberries and first crop of tomatoes and I like what I see so far. I interplanted some lettuce in the strawberries and they look great. I will plant more lettuce on plastic next year.”

Ellen writes, after a wet spring and still receiving almost daily rain in the middle of June, “I have never experienced such a time, and neither have even the old timers around here… The soil has been dry enough to hand hoe only, and that was just one afternoon this week. Needless to say, the weeds are going crazy. Again, I'm envious of my neighbor who uses black plastic, cause the weeds are limited, the root zone is warmer and those plants are WAY bigger than mine.”

Alvin thinks is unacceptable to use plastic mulch.

Ken calculates amount of plastic used to grow a head of lettuce is 1.25 sq ft/head of lettuce. Nobody thinks anything about putting lettuce they sell in a plastic bag, which is about 2sq ft. of plastic.

Tim likes Ken’s plastic mulching system, as shown on the video [click here for video details] “I need to grow all my peppers, melons, tomatoes and eggplant on plastic next year. I have my cover crops growing for those particular beds with a couple more beds being set aside for more cover cropping of vetch, elbon rye, and austrian winter peas.”

Ellen’s ready to incorporate plastic mulch into her operation: “What brand of plastic do you recommend I try? smooth or embossed? black, I'm assuming since I will only use it for my first plantings of toms, peppers, eggs and cucurbits. Any other things I should worry about before I buy the layer - I'm headed for a flat bed layer from Rain-Flo in Pennsylvania that should run me $1300 plus shipping.”

Rosie responds: “In case you didn't notice, we had the flat bed Rainflo down here. It's set for the Type I three point hitch standard, although I'm sure they can make it otherwise. I don't know what size your tractor is--bigger than 35 hp or so it'll be a Type II hitch. I almost made a mistake when we ordered and would have had to eat double shipping costs. A bigger tractor basically would allow you to spend more and buy the raised bed version. I didn't know there was a smooth or embossed choice in plastic. What difference does it make? We've almost always used black, although early on we tried white and a reflective one once for an experiment. Generally, we like the black to trap more heat.”

Ellen wants to know if onions can be planted on plastic mulch.

Nicolas responds: “I planted my onions in black plastic this year and I love the way they look, with not weeds. We planted 3 to 4 rows per bed with 3 drip tape under the plastic. We only had to weed once around the onions. I am harvesting some now as green onions. So much easier than with straw.”

Tom and Rosie respond: “We've done (and are doing) onions on plastic, with better results than not.  Leeks as well.  They (the onions at least) seem to like the extra heat the plastic affords.  Don't know about water use under plastic versus straw, but in general the plastic conserves it well.”