Friday, 3 November 2017

Pesticide-Free Maize 2017

Intermittent reinforcement is a powerful psychological effect. As we head into our third season of growing maize without pesticide, I'm hoping for the stunning results we got in our first season and trying to forget the disappointments of last year, when we got slammed by the weather and the weeds. Somehow I forgot to blog about that. It wasn't a complete disaster (we're feeding out the silage now) but it was pretty bad: We comforted ourselves that everyone around here had a bad maize season.

But I still have a vivid memory of sitting in the silage chopper harvesting tall healthy maize from our first attempt, and hearing the surprise in the contractor's voice about the size of our crop which he knew damn well had flouted almost all industry recommendations, and the nice big pile of silage we had at the end. So yeah, we're doing it again.

The basic plan hasn't changed: feed the maize plants well but don't poison predators/competitors. We buy bare hybrid seed, untreated with any insecticide or fungicide. Before sowing we innoculate the seed with our own blend of beneficial fungi (mycorrhizae and trichoderma). This year we're including the wonderful aztobacter. The picture shows a bag of untreated maize seed tipped into a wool fadge with a dollop of each innoculant on top. We roll it around in the fadge to coat the seed, and then tip it into the drill for sowing.

Preparing the Ground
But I'm getting ahead of myself. The most difficult and crucial part of this process is getting the maize away to a good start before it gets swamped by competing plants. It's all good when the maize beats the weeds to canopy closure, at which point the maize blocks light to everything else, but a disaster otherwise.

In previous years we've got the contractors in to disc the maize paddocks and then power-harrow (rotary hoe) them. We're keen on and have tried to use false seedbeds but the logistics beat us both times: we just don't have time in spring to wait for dormant seeds to sprout. Since we have no discs or power-harrow, we're also dependent on contractors for the timing of cultivation. Received wisdom also dictates that maize be "precision planted" so contractors again.

Herbicide helps manage these logisitics: just spray out the paddock. If there was much grass when you sprayed, put some animals in there to eat it before you the disc, power-harrow etc. I'm serious: NZ farmers do send cattle into paddocks that have been killed with Roundup.

Fortunately though, animals are also a herbicide substitute. This year we break-fenced young stock on the maize paddocks, pushing them a bit hard, aiming for very little grass cover, plenty of trampling, but not quite raw earth/mud. It worked very well for one paddock and most of the second but then the contractor was discing in the neighbourhood so we got all three paddocks disced, rather than wait who-knows-how-long for the next chance.

We are trying less cultivation this year, because it really messes with soil biology, slicing up the worms, destroying those wonderful hyphal networks and releasing CO2. Maize seed is large and robust: it is a kernel of corn. It should be able to grow from a shallow seed bed. So we're skipping the power-harrow stage. After discing, we crumbled up the top 2-5cm a bit with our own gear and then drilled the maize seed directly into that.

Sowing the Seeds
As mentioned above, the normal system involves "precision planting". We bought this service the last two years but are trying an alternative this year. Based on the last two years, we reckon that:

  • "precision planting" involves nothing more than setting the row width at 750mm and then dropping seed to achieve a target of seeds/ha; and
  • in practice, the spacing of plants in those 750mm rows is random - it hits the target sowing rate on average but plants are not evenly spaced in the rows.

Our contractor, who also supplies the planting service, doesn't care about row width because his chopper has a rotary head: it'll eat anything. So row width isn't a concern for harvesting, but canopy closure is the #1 issue for succeeding without herbidice.

I won't bore you with the arithmetic, but it's easy to show that random planting at the same per hectare rate would give much more uncontested space to each maize seed, which should also mean less maize-maize competition and faster canopy closure. We happen to have a great seed drill perfectly capable of random planting at a specified rate.

So that's what I did last night: drilled the seed randomly in 2 paddocks and made a start on the third before retiring due to an over-heating tractor and and under-fed driver. Since then we've had 30mm or rain.

After the storm, the next jobs are to get the drilling finished, roll the paddocks, and then get the fert on! 

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