Organic weed control methods / herbicide?

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paradoxbox
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Organic weed control methods / herbicide?

Post by paradoxbox »

Alright, I dug up both of my fields twice, once last year and once this year and mulched them both (with dead leaf, grass, straw etc), but the land was abandoned for too long and as the saying goes "1 year of seeding means 7 years of weeding". This land was left wild for about 1 or 2 years before I moved in so the seeds got everywhere.

The weeds are just impossible to deal with by myself without machinery - more drastic measures are going to be needed.

I don't really want to spray harsh chemicals as my goal was organic but the weeds are just so thick in some areas it seems like it may just be best to blast the field twice, once before rainy season and once again after, then try to go organic from then on.

Any ideas / opinions on what to do? The weed growth is really quite bad. I am cutting them down for now, to prevent seeding, as it's too much work to dig the fields up completely by hand again, and I am sure digging will just make more seeds germinate. But the weeds are so thick that the field is looking more like a meadow than a field.

Currently I'm hand weeding my most sensitive crops, don't have a rototiller and there's no budget for one right now. The weeds have pretty much killed a few rows of my weaker crops so something has to be done. I've managed to deal with the pests by having some sacrificial komatsunas and spinach but the weeds are relentless.

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Eric in Japan
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Re: Organic weed control methods / herbicide?

Post by Eric in Japan »

How big is the area? I am sure you have heard about sheet mulching, but maybe for some of the other readers:

1. Go to your local home center, lumberyard, or construction site and ask if they have any old lumber wraps you can have. They are like the blue tarps but usually opaque.
2. Cut the weeds down to ground level. You might want to scatter some cheap chicken manure.
3. If you have access to lots of cardboard or better yet newspaper, lay them down overlapping over the whole field, and water it well. Use at least five sheet thickness of newspaper. When it gets wet, it will conform to the ground. Cardboard usually doesn't, and a very few of the weeds might survive.
4. Then just lay the lumber wrap down over the whole thing (weighted along all the edges of course). The weeds will suffocate, and worms will eat the cardboard/paper and suffocated weeds over the course of the year. If you don't like the look of the plastic, cover it with straw, rice hulls, or leaves. Not too thick, you will probably want to remove the sheet later.
5. You can cut a circle out of the paper and the wrap to fit your seedlings down into. Now you only have to weed a small circle around the transplants until they are established.

I have done smaller areas (4x5m) this way, and it works great for potted seedlings, and especially pumpkins and watermelon. But not so great for direct seeding. To adapt it to an existing garden, you can cut the lumber wrap in strips and mulch the lanes to at least cut down on the weeding But it might be better to write off some of the field and have a wide blank canvass again... Once the weeds are suffocated, you can move the plastic to the next area and mulch the first one with paper and a minimum 20cm of straw or fall leaves. (don't till it!) You usually only need the plastic for the super weeds of the first year.

To plant a row of carrots for example, I would cut a rectangle out of the sheet, leaving the paper. Then put 5 cm or so of potting soil into the rectangle, and with a sharp stick or take-gushi poke holes through the dirt and paper, and plant the carrots in the potting soil above said hole. The roots hopefully will find their way through.


But my favorite way is the classic square foot garden. So easy to plant, water, mulch, and weed. This year I made a sheet mulched square foot garden. Working brilliantly!
"... so, the cucumbers said to the cabbage, `Lettuce Go.`"

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Zasso Nouka
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Re: Organic weed control methods / herbicide?

Post by Zasso Nouka »

You can use the stale seedbed method. Prepare your seed bed in the normal way but do it three to four weeks before you want to use it and then water it and keep it moist over the next few days or prepare the bed just before some rain is due. Now wait for the weeds to germinate, once the weeds have germinated flame the bed or lightly rake the bed over on a hot sunny day in the morning so that the weed seedlings dry out during the day. If the seed load in the soil is really heavy you can repeat the process several times before planting your vegetables, the key is to only really lightly rake the bed so you don't bring any more weed seeds to the surface.

Another method is to solarise areas. For this you'll need some clear plastic mulch. Dig the area over and cover with clear plastic mulch. Seeds germinate and then are cooked under the clear mulch by the sun. If done in the summer it can sterilise the top centimetre or so of the soil with the high temperatures achieved. You can then either plant your veggies or dig the patch over and re-cover to sterilise the next few centimetres.

Grow green manures that out compete the weeds. Sorghum (ソルゴ) is particularly good for this during the summer and Italian Rye Grass is a good winter cover crop. However you are going to need a kusakari-ki to cut them down (could do it by hand in a small area) and digging in Sorghum by hand could be difficult, if you can borrow a rototiller or have a neighbour run a tractor over it that would make the job much easier.

Black plastic mulch, this one is a sure fire success and helps gradually reduce the seed load in the soil. Prepare you bed normally but dig a shallow trench down the sides, we're not talking deep or wide just enough to bury the edges of the mulch. Water the bed well or wait for rain and then cover with the mulch and secure the ends and edges and plant your young vegetables in through holes punched into the mulch or seed directly in smaller holes. I'd recommend going with at least the 135cm wide mulch or even the 150cm wide variety to keep weeds from invading the seed bed from the edges, don't bother with the 90cm wide rolls. This may seem to be environmentally unfriendly but you can recycle the mulch after you've used it and if you plan your plantings well can be used for several successions of crops. I have to say when I first started farming I was against using the plastic mulch on environmental grounds but after loosing so many crops to weeds and seeing that all the other organic farmers use it we were won over. Because weed seeds germinate under the mulch but then die from lack of light this method will gradually reduce the seed load in the soil.

You can also use crops like potatoes to help reduce weeds as they will smother weeds around them and you generally harvest them before the surviving weeds can set seed.

Running a kusakari-ki along the soil so that the tips of the disc are disturbing the top few millimetres of soil is a great way to keep weeds clear from pathways between your beds but on a smaller scale you could achieve the same results with regular hoeing. Keep the kusakari-ki disc sharp as running it through soil dulls the tips quite quickly, same for your hoe. Right now our local Komeri is selling 4 stroke Makita kusakari-ki's for half the listed price to clear out last year's model for this year's one.

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Re: Organic weed control methods / herbicide?

Post by xxxxtom »

So I've only being attempting veggie growing for a few months and weeds appear to public enemy no 1 . I couldn't understand why plastic sheeting was so popular. Now I'm beginning to understand why. I'm still a little surprised that ZN and Eric also use plastic. I know almost nothing about gardening but isn't that method unnatural, doesn't it suffocate soil ecology or something or is it that when weeds are so bad used short term it is the most effective alternative?
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Re: Organic weed control methods / herbicide?

Post by Eric in Japan »

Plastic is unnatural, but then again, so is tilling the soil.
I don't particularly like plastic, but I like it better than losing all my garden to weeds. It is a compromise. I use it in the fields furthest away. Where I sometimes don't make it to pull weeds for a week or more at a time.

As for suffocating the soil ecology, it doesn't seem to. Quite a bit of air comes through the holes you have planted in, and earthworms seem to love it under the plastic mulch. And it definitely helps keep the soil moist.
"... so, the cucumbers said to the cabbage, `Lettuce Go.`"

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Re: Organic weed control methods / herbicide?

Post by Zasso Nouka »

I agree with you both that plastic seems unnatural but as Eric says it is way better than loosing your entire crop. Also as he points out it doesn't seem to harm the soil and on the contrary seems to protect it from drying out in the intense sun of summer and actually nurtures soil life, it also helps reduce soil compaction during the torrential downpours of the rainy season and stops a dry top layer blowing away in the wind.

We've been using it for 5 years now and I don't anticipate stopping any time soon, there seem to be just as many weed seeds in our soil now as when we first started and they seem to get refreshed every few years as we rotate our pumpkin patch around the hatake. It's impossible to keep the pumpkin patch weeded once they go ballistic in the summer so by the end of the season there are plenty of weeds growing to refresh the seed load.

On a small scale where you are there all the time to hand weed it is possible to do without it but it's nearly impossible to keep 5,000 tsubo weeded by hand.

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Re: Organic weed control methods / herbicide?

Post by paradoxbox »

I think I will give the plastic a try then, but the weeds are REALLY bad so first I'll go over it with a machete or knife. (Don't own a kusakariki, no budget for it this year)

To put some perspective on it, I have had 4 layers of cardboard down on the whole field since last October just after I moved in here, and the weeds just pushed through it like it was nothing. When I pulled up some of the cardboard to check what was going on, it was a huge mass of matted weed growth. The growth is white but it's still there and sucking up nutrients from the soil. I have removed the cardboard since it wasn't having enough of an effect.

At this point I'm still debating whether to till the soil with a hoe once more, digging manually is a lot of work since it needs to be dug a full spade or deeper to break up the compaction. But I suppose with all the plant matter growing on top now it will decompose and loosen the structure a bit.

The fields are about 15 meters wide by 50 meters long of dense clay soil.

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Re: Organic weed control methods / herbicide?

Post by Zasso Nouka »

Weed seeds really are a gift that keeps on giving, for many many years and there are some other bonuses they throw in for free as well. Many insect pests have their natural home in certain weeds but will happily move into your crops and devour them. Nekirimushi (cutworms) love living in amongst grass roots where they seem to do little harm to the grasses that quickly regrow but should they venture into an area of young crop seedlings you can quickly see your entire harvest devastated. Kisujinomihamushi (flea beetles) also find a home in many weeds and can cause quite a bit of damage to young brassicas or members of the Solanaceae family so keeping weeds well away from your crops can help keep those pests down.

We tried living mulches to suppress weeds early on but they can easily get smothered by the weeds or attract the above mentioned pests themselves so we don't bother with them now but might try again in a few years when we've reduced the seed load in the soil.

To break up the soil you could dig momigara into the ground, that aids aeration and stops compaction. Turning it into charcoal is also very beneficial and helps retain nutrients and provides a home for beneficial bacteria and fungi. You should be able to get it for free from local rice farmers who might deliver it for you instead of carting it off to their tanbo to burn.

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Re: Organic weed control methods / herbicide?

Post by paradoxbox »

Happy weekend everyone.

Yep I have asked the local JA and farm store people but there are no rice farmers near here - too mountainous. Everyone seems to grow the same crops here - potatoes, norabou, negi and some people grow onions cabbage and lettuce. The diversity is pretty lame! No ricers here.

I will give a light hoeing a try tomorrow morning before the rain, wait a bit for any new seeds to come up and then hoe again to kill anything that comes up.

I think I will also buy a few big bags of clover and hairy vetch. Not really the best season to plant but I noticed that certain areas of my crops were growing very slowly while others were growing very well. The past owners definitely over-farmed certain areas with potatoes or some other demanding plant.

Will post up once the work is done..!

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Re: Organic weed control methods / herbicide?

Post by Zasso Nouka »

If you plant hairy vetch at this time of year it will just flower and won't bother making much significant growth, you need to plant it in the autumn. The seeds will store quite happily till then. Clover will enjoy the rainy season which will give it a chance to establish but will probably stall or die back somewhat in the intense heat of summer (depending how hot your location is) but it will rally in the autumn and grow back.

Shame there aren't any rice farmers nearby. If you have any groves of bamboo nearby you could still make take sumi to use as biochar to improve the soil, the process is quite straightforward. You can use the brown dead poles to make the biochar so you don't have to cut down and strip live green poles, you can use live poles but they hiss and spit a lot and the dead ones are a lot easier to start burning.

Good luck :thumbup:

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