NZ Lifestyle Block

Farm diary

Spraying weeds is easy, but it turns out organic methods can give you the same results if you do it right. Here are 16 practical ways to control weeds without using chemicals.

- Words Nadene Hall

16 tips for spray-free weed control

It’s a common myth that organic farms have more problems with weeds. But research by weed scientist Kerry Harrington at Massey University found that isn’t the case. A comparison of two similar farms, one organic, one convention­al, over eight years, found the rate of weeds in pasture was the same (approximat­ely 5%).

While you save time (not spraying) and money (not buying chemicals), organic weed management requires placing more emphasis on soil and pasture health.

1 Walk your property

If you have animals that know you well and follow you (vs those you need to herd), you may rarely walk over your pasture. However, regular checks are vital to successful organic weed control. You're more likely to spot weeds when the area affected is small and easily managed by hand-pulling plants.

2 Don't let weeds flower

Once plants flower, most quickly go to seed. It's crucial to take action, such as hand-pulling or mowing before they flower, so the problem doesn't get larger.

3 Mow

Cut weeds down when they're young and vigorous, with dense leafy growth, to deplete their root systems. Leaves provide crucial nutrients to the root system via photosynth­esis. Regular mowing stops the roots from building up a nutrient bank. Eventually, they die from lack of nutrition.

Research by the University of Wisconsin showed one mowing in the growing season of annual weeds and multiple mowing of perennial weeds when they're 20-30cm high (before flowering) will kill them off.

Mowing also stops weeds from shading out ‘good' pasture plants such as ryegrass and clover.

The key is to mow higher, so you cut the leaves of weeds. You don't want to scalp an area down to bare soil (as weed seeds will germinate), or cut back useful pasture plants too low (or they'll stop growing too).

4 Don't overgraze

Animals prefer tasty plants such as ryegrass and clover and will graze them down to ground level if given the opportunit­y. They also won't eat most weeds. The result is the weeds get bigger, and the grass and clovers suffer (or die) due to lack of leaves. Ideally, move stock on while the pasture is still 5-8cm high, giving plants enough leaf area to feed the roots, which can then grow new stems.

5 Graze multiple species

Grazing animals eat in different ways:

• cattle (preference grass, legumes) prefer to graze the top half of a plant;

• sheep (grass, brushy plants, young weeds,) and horses (grass) like to bite plants off quite close to ground level;

• goats browse, preferably on young trees, shrubs, and brush, at or above head height – if eating pasture and weeds, they mostly nip off the tips.

The result of cross-grazing with different species is more uniform and efficient use of pasture. Weedy plants get less of an opportunit­y to dominate an area because they're grazed to the same level as the grass and don't shade it out.

Horses are notoriousl­y picky eaters. Sheep make excellent pasture partners as they prefer to eat a lot of what horses will leave behind.

You also need animals that suit your terrain. Sheep and goats tend to be better grazers on steep hills than horses and most cattle breeds.

6 Rotate stock

When you have small stock numbers, it can be tempting to place them in a paddock and leave them there to graze for long periods. However, this leads to over-grazing of palatable pasture plants and under-grazing of less palatable ones and weeds.

Over-grazing eventually kills off ‘good' plants, leaving bare, depleted soil. Hardier weeds are then more likely to germinate.

Smaller paddocks are an excellent option for cattle. They're naturally competitiv­e over feed, making them more likely to eat less palatable weeds such as dock.

7 Don't help weeds to spread

One of the common ways to introduce a weed to your block is in hay, manure, compost, or when seeds or stem fragments come in on machinery.

• Check the reputation of feed and fertiliser suppliers (and transport companies who deliver it) and the cleanlines­s of machinery and other vehicles that come onto your property.

• If you’re using your mower or tractor to cut down weeds, make sure to clean it and the mowing deck when you move to a new area. It prevents the spread of seeds or stem fragments that could easily resprout (eg, kikuyu).

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