7 ways to fight weeds or­gan­i­cally

NZ Lifestyle Block - - FEATURE - WORDS NADENE HALL

It’s the eas­i­est thing in the world to get a chem­i­cal, add some wa­ter and spray and voila, within a week a pesty weed is gone. But if you’re more in­ter­ested in be­ing kinder to your land, its soil and the health of the crea­tures liv­ing in it, you will need to take a longer-term view of deal­ing with weeds.

It’s a com­mon mis­con­cep­tion that or­ganic farms have more prob­lems with weeds, but re­search by weed sci­en­tist Kerry Har­ring­ton at Massey Univer­sity found that wasn’t the case, with his tri­als over eight years show­ing the weed com­po­nent of pas­ture on an or­ganic test farm was the same as a con­ven­tional test farm, ap­prox­i­mately 5%.

His work found the con­ven­tional farm had more pas­ture growth over­all, prob­a­bly due to ap­pli­ca­tions of urea, some­thing not per­mit­ted on the or­ganic farm. As a re­sult, the or­ganic farm (which used com­posted chicken ma­nure) was un­der more graz­ing pres­sure, and its main weed species was hairy and creep­ing but­ter­cup (vs dock on the con­ven­tional farm). NOTE: both farms used soil tests and reg­u­lar ap­pli­ca­tions of fer­tiliser, lime etc, an im­por­tant as­pect in terms of the health and vi­a­bil­ity of ‘good’ pas­ture plants.

Walk your prop­erty reg­u­larly

Even if you have a small block, it can be easy to not walk over the en­tire area, es­pe­cially if you have an­i­mals that know you well and will come to you, vs herd­ing.

But the key to suc­cess­ful or­ganic weed con­trol is to get onto weed plants when the area af­fected is small so they don’t get the chance to go to seed or to spread (which weeds are very good at do­ing, very quickly), sav­ing you time and money.

Don’t let weeds flower

Once a plant gets to the flow­er­ing stage, it will quickly go to seed. Also, by con­trol­ling weeds, es­pe­cially perennials, when they are young and vig­or­ous, you de­plete the root sys­tem, mak­ing it more dif­fi­cult for the plant to re­grow again so they be­come smaller and smaller, be­fore giv­ing up.

If you can’t use her­bi­cides, cul­ti­va­tion is your best bet

In Dr Har­ring­ton’s study, the or­gani farm used a mould­board plough, then left the soil to fal­low for 3-4 weeks, cul­ti­vated it again, planted a crop of turnips, then cul­ti­vated it again af­ter the crop and re­sowed it with pas­ture the fol­low­ing au­tumn. Both the or­ganic and con­ven­tional farms found they had weed is­sues in the year af­ter sow­ing, but a year later, the ra­tio of pas­ture to weeds was sim­i­lar.

A mould­board plough turns and buries a layer of top­soil, bury­ing weed seeds so they are un­able to ger­mi­nate. Re­search has shown this type of plough­ing also helps the crop to grow as the sub­soil al­lows a lot of wa­ter to pass through it, soak­ing into the top­soil and giv­ing a boost to the de­vel­op­ing roots of plants.

This will mean you’d need a con­trac­tor to come in to cul­ti­vate and later un­der­sow (un­der­sow­ing is vastly su­pe­rior to over-sow­ing), and you’d need to have any pas­ture mown to a very short, al­most scalped length be­fore at­tempt­ing to cul­ti­vate it.

Mow your this­tles

There’s now NZ re­search which shows mow­ing Cal­i­for­nian this­tle at spe­cific times of the year is a great way to kill it off, but mow­ing off other this­tle species makes the plants more palat­able to stock if they are al­lowed to graze the cut-off re­mains soon af­ter.

The regime for mow­ing off Cal­i­for­nian this­tle is out­lined here: http://beeflambnz.com/cal­i­for­ni­anthis­tle

Graze mul­ti­ple species

Graz­ing an­i­mals graze in dif­fer­ent ways: • cat­tle (pref­er­ence grass, legumes) graze to about mid-height; • sheep (grass, brushy plants, weeds) and horses (grass) graze down to ground level; • goats browse, prefer­ably on young trees, shrubs and brush at or above head height.

Cross-graz­ing with dif­fer­ent species means more uni­form and ef­fi­cient use of pas­ture so weedy plants get less of an op­por­tu­nity to dom­i­nate an area be­cause they are grazed to the same level as the grass and don’t get the chance to get ahead. For ex­am­ple, horses are no­to­ri­ously picky, but choose an an­i­mal that grazes dif­fer­ently like goats or sheep, and you have more of a bal­ance to the pas­ture plants present.

It also means you can use the right an­i­mal for the right ter­rain; sheep and goats do bet­ter at han­dling steep hills vs horses or cat­tle which are de­signed to move best on flat land.

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, but this leads to over­graz­ing of palat­able pas­ture plants, and un­der­graz­ing of weeds or those less palat­able. Over-graz­ing kills off ‘good’ plants, leav­ing bare, de­pleted soil, al­low­ing ‘bad’ plants to take over as they are stronger, and more likely to do bet­ter in a de­pleted soil.

Smaller pad­docks also en­cour­age cat­tle to nat­u­rally com­pete with each other for the feed on hand, mean­ing they’re more likely to eat weeds such as dock.

Don’t help weeds to spread

One of the com­mon ways to in­tro­duce a weed to your block is to bring it on in hay, or to spread ma­nure laced with weed seeds. Don’t let weed plants go to seed as your live­stock then eat and spread the seeds, neatly pack­aged in a per­fect, ni­tro­gen-heavy medium (ma­nure).

If you are us­ing mow­ing to cut down weeds, make sure to clean your equip­ment ev­ery time so any seeds or grass residue (eg, kikuyu) don’t get spread to other ar­eas of your block.

Strate­gic mow­ing of this­tle species can kill them off over time.

Creep­ing but­ter­cup

(Ra­nun­cu­lus repens).

Mould­board plough­ing cuts roots and helps to cre­ate a weed-free bed for sow­ing new pas­ture.

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