Microplot garden design – 1

One of the things I’m experimenting with is dense microplots for urban gardens. Take three, maybe four species of food or useful plant, and grow them together in a complementary fashion so that they each help each other thrive and produce. Most urban gardens don’t have very much space, and there’s always a temptation to plant all the everything – but what you end up with at harvest is two lone roma tomatoes, a single sweet corn, and some bolted lettuce. More effective is to plant plenty of a couple of things, so that you have all of those that you could wish for plus spare to swap with a neighbour – who is hopefully growing something different. It’s a distributed model of smallholder farming – you grow the this, we’ll grow the that, and we’ll share. It means a little less effort and concentration on your part because you’re only trying to keep a couple of types of things alive for a set period of time. But it also means that if you screw up on something, you lose all of that particular crop. What seems like it would be useful would be some practiced microplot designs – combinations of food plants that are tested to grow well together, need the same kind of water and fertiliser regime – take some of the guesswork out of it. I’ve been playing with various microplot designs over my time here, experimenting with novel crops as well as the familiar garden favourites in order to build up some suggestions. I’m going to post a few of them across the next little while, warts and all.

The one I’ve got most active at the moment is in my drylands zone. It’s a space about 2.5m wide by 4m long. It gets watered once a week throughout Perth summer – which is half the permitted amount and a lot less than most vegie plots would unofficially get. The three crops I chose were cowpea, broom-corn sorghum and watermelon. They’re all sow-in-spring, warm-season crops. I hoped that the cowpeas would help provide nitrogen to the others, the watermelon would help shade and protect the soil, and the sorghum would give a limited amount of canopy to take the edge off the heat for the lower plants. Cowpea is a cooking legume – harvest when dry, store sealed and then cook when needed. The broom-corn sorghum is best for feeding wild birds or chickens, and its roots make good, extensive soil conditioner/developer. The watermelon needs no explanation.

What I learnt: first, planting them all as seeds at the same time didn’t work. The sorghum and the cowpea need soil moisture protection to reliably germinate in our warm spring. I allowed weeds to grow through the patch for the first month or two, and wherever the weeds had sufficiently protected the soil moisture, I got germination. The plot I’m working in is (like most of my garden) highly hydrophobic and I didn’t fix that well enough before starting. That’s a problem for sorghum – ideally, it has good soil moisture all the way through the profile and then only limited rain while establishing, if I’ve understood correctly. The watermelon just didn’t get established quickly enough or well enough to cover the soil. Some of that was water and the hydrophobicity, and some of that was timing vs soil warmth. Starting the watermelons as seedlings a few weeks ahead of planting the main bed might have worked a lot better. Or planting the seeds into an existing microplot that was running on a winter design and still had some soil cover.

Second, the watermelon. I first planted an early-season watermelon with the intent that most of the cropping would be done by the end of Birak or firstsummer, which is around about January 21st give or take ten days. When most of those seeds failed to germinate due to the soil moisture issues, I planted in some random hybrid seedlings that I picked up in a punnet somewhere. These kind of went along without doing much, until at the start of Bunuru or second summer, at the end of January, we had a week of steady rain followed by a return to the usual hot weather – and the sun had moved sufficiently that the surviving melon plants got an extra two hours of shade in the morning. At this point the watermelon plants that had survived went bananas, or rather melons, and spread everywhere. So water vs warmth vs light needs better managing for these guys, as they won’t have enough warmth left in our season to get fruit through to harvest now. I will try again next year with another early-season watermelon, and concentrate on the soil moisture.

Third, the broom-corn sorghum. I really enjoyed growing this plant. I recalled that the farmers who grow sorghum broadscale didn’t like getting additional rain during the season, and I wasn’t sure how the regular watering that the watermelon needed would affect the sorghum. It turned out to be OK though, if not better than expected. What I’m seeing (and I think I’m right but don’t completely know yet!) is that the extra watering – especially that week of rain – causes the sorghum to put up extra grain heads or tillers. Which is a problem if you’re broadacre harvesting, because you want all the grain to be ready at the same time. But in an urban microplot, extra grain at staggered times is much better.

Fourth, the climate suitability. These plants have all done fine so far across our four months summer, with watering at best every 6 days and sometimes only every 2 weeks. The cowpea mostly flowered and set seed early in the season, so in combination with early-harvest melons that means the bed could remain at reduced watering across secondsummer (our harshest time for plants). Shade was an issue – one half of the bed got an extra two to three hours of morning sun across Birak (roughly Nov 21st to Jan 21st), and that half of the bed had a) no sorghum germination and b) very little plant survival through to flowering. So even shading will be a consideration for replicating this bed design out to others, as will total sunlight hours. The bed gets full sun for most of the day, which all three crops like, but apparently there is such a thing as too much.

Conclusion: this bed design has a lot of potential and should eventually become a highly-suitable design for distributed urban farming in Perth, but I need to run it at least a second time (if not a third or fourth) and see what else I can get wrong or right.

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