Optimizing Your iAVs Sandgarden

GD….I was going to use this in the last unit in the course but I have decided that it’s probably better suited to use as an introductory section in the next Course…How to Optimise an iAVs.

Throughout the manual, we’ve stressed the ‘simple and easy’ aspects of the iAVs method.  The Starter iAVs is a simple design that is easy to create.  It is easy to set up and simple to operate.

It was originally conceived for use by impoverished people.  It is the quintessential ‘fit for purpose’ food production system.  It has…and needs…nothing but itself.

While Sandgardening has a proven heritage, we have not established a production ceiling for the method…so there’s considerable scope to enhance the performance of your Sandgarden by ‘tweaking’ the production parameters.

There are dozens of variables ‘at play’- every day.  Changing one aspect/parameter WILL influence everything else eventually.  

This is the ‘nature’ of an integrated “SYSTEM” – to know what is actually happening in your system (pH, temp, DO, feed input/quality, FCR, etc.).

Observe what is happening carefully and often.  

Observe, assess, adjust, observe, assess adjust, repeat, repeat – repeatedly.

Environmental Control

All living organisms grow and function best in a particular environment. 

For Sandgardening purposes, the living organisms include fish, plants and the uncountable variety and number of soil microbes that inhabit the sandbeds.

The environmental factors that we’re looking to manage (optimise) include:

  • Temperature
  • Humidity
  • Light intensity, duration and colour spectrum.
  • Dissolved oxygen.
  • pH
  • Nutrition
  • Disease and pest control

The temperature will impact your choice of fish species and the types of plants you can grow – and when you can grow them.  

The amount of natural light that is available to you will also directly impact plant production. 

You can grow plants in a basement or warehouse that never sees sunlight – but providing artificial lighting of the correct photoperiod, intensity and spectrum is probably going to be the biggest cost associated with the construction of your system. And it will almost certainly be among your biggest operating costs.

A controlled-environment-cropping greenhouse is a more cost-effective proposition since you save on energy costs while still being able to regulate all of the other operating parameters.

Maintain air temperatures and humidity levels appropriate to the plant species being grown. 

Shade, fogging, and evaporative cooling can each be effective for cooling, either individually or in various combinations.   Always provide ample ventilation and continuous air movement within a greenhouse.

Fish Feeding

Let’s assume that you are starting with

While there’s nothing wrong with that prescription, we can, with a little effort, do better.  Doing better, in an iAVs context, means more fish…and more fruit and vegetables…for less water and energy.

Doing better requires that we measure the total weight of fish biomass in the tank.  Weighing every fish is just hard work…so we catch and weigh just ten fish.  Working very quickly, we pat the fish dry with clean paper towel before putting it on the scale.

As soon as the weight is noted, release the fish back into the tank.  Repeat this process a further nine times.  Add all the weights together and divide that total by 10 to arrive at an average weight per fish.  Multiply that figure by the number of fish in the tank and you have the total weight of fish biomass in your system.

Once you have that figure, you’re able to adjust your feeding rate t achieve balance between cost-effectiveness and 

Mark McMurtry demonstrated that each 1.0 kg of fish weight gain provided sufficient quantities of all required plant nutrients to sustain 2 tomato plants yielding 5-7 kg of fruit per plant over 3 [to 4] months depending on cultivar and climate.

For example, if you started out with ten 10g fish and you grew each of them to 110g – a total of 1100g – you have sufficient nutrients to produce 10 – 14kg of tomatoes in three months.   

Fine-Tuning

As much as we advise against operator discretion for the reasons we’ve stated, there is scope to fine-tune an iAVs to take account of different plant management profiles. Such ‘tweaking’ includes adjustments to the intermittent irrigation frequency and timing to suit particular climates or variations in sand bed drainage rates.

When considering

Intercropping

This is arguably the quickest way to enhance the performance of your sandgarden.  

Intercropping involves planting complementary species in the rows between plants like tomatoes, cucumbers and other vines and climbers.   

Tomatoes will shade out other smaller plants eventually so fast-growing plants like radishes, soft herbs and Asian/salad greens are ideal for intercropping.  

You’ll be enjoying salads from your sandgarden while you’re waiting for the slower-growing plants to mature.

Integrated Pest Management

Let’s be clear.

As good as Sandgardening is, it is no less likely to attract insect pests than any other gardening method so we need a strategy to ensure that we can control those pests that could deny us our share of the bounty of our Sandgarden.

You need to take every precaution to prevent pests and diseases from entering your greenhouse.  A common vector is humans: limit and pre-sanitize all visitors and workers. 

Use insecticidal soaps (Potassium salts of fatty acids) and plant-based extracts with care (minimize/eliminate contact with filter substrate).

Use integrated pest management strategies extensively (employ beneficial insects, bacteria, and disease and pest-resistant plant cultivars). 

Plant Culture

Many plants have specific cultural needs (like trellising, pollination, pruning, training, etc) that are additional to those that we’ve already spoken about.  Applying sound cultural practices is vital if you are to realise the potential of your sandgarden.

You’ll eventually reach the point where you want more food or greater variety in your diet.  That’s when it’s time to expand your garden.

Summary

My coverage of these topics – given the time constraints of an introductory course like this – is little more than an overview.

My brief in this course was to enable others to build and operate an iAVs Sandgarden. An ‘Intermediate’ course that focuses on the how-to of “Optimising an iAVs Sandgarden might be on the horizon.

-o0o-

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