Deep Water Cultivation Page 4

The bucket version of a deep water cultivation system.  The bucket serves as both the individual reservoir, as well as a bottom-heavy counterweight to what often is a top-heavy plant.  This approach is most commonly used in two scenarios: when a grower wants to experiment with this method on a very small scale, and/or when the desired crop is a long-lived, top-heavy species such as tomatoes or other vining plants.  The reservoir serves not only to feed the roots but also to keep the plant upright and anchored.  If experimenting with extremely large plants, try to avoid using tall, narrow buckets since this would still allow the plant to tip over.  For smaller plants such as lettuces and small herbs, a medium-sized bucket could grow one large or several smaller plants.  Image courtesy of

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Estimated Cost for Deep Water Cultivation

Thanks to its simplicity, deep water culture can be one of the cheapest possible hydroponic methods.  For hobbyists, a small Rubbermaid tub, some rigid Styrofoam insulation, a few net pots and an aquarium pump with air stone will be sufficient.  However, commercial growers will benefit from more dedicated infrastructure.  Many hydroponic retailers provide a variety of rafts with pre-cut openings for different crops, based on how large those crops get at maturity.  Having pre-cut rafts can save a tremendous amount of time and labor when setting up the system.  Along the same lines, those rafts are rigid plastic which can withstand years of repeated use, needing only a mild cleaning in between.  Rigid Styrofoam rafts will deteriorate over time, due to abrasion, flex and wear/tear as the crops are repeatedly put into then taken out of the rafts.

The air pumps and airstones are rarely ever a cause for concern, because even large reservoirs can do well with relatively small air pumps and airstones.    However, growers working with marginal crops, such as those which need higher than average oxygenation at the roots (ie, the so-called dry-loving plants), should invest in more air pumps and airstones than what they’d need for moisture-loving crops.  Additionally, those pumps and airstones do eventually wear out.  The airstones in particular can eventually get plugged up with algal growth and debris from growing plants.  They’ll eventually need to be replaced.

The last remaining cost specific to DWC is the reservoir itself.  As we’ve already discussed, the reservoir cost will depend upon its size and structure.  This in turn will depend upon the crop being grown, the size, depth and insulation required (if any).   If growers already have a reservoir to work with, that can be an asset as long as the reservoir is still water-tight, and as long as it’s at least close to the desirable size and dimensions.  One important note: most commercially available rafts are only available in a few different sizes, with 2’ x 4’ being the most common.  So the reservoir will need to be sized to make the most of those dimensions.  If working with a pre-existing reservoir size, a grower will either need to build odd-sized rafts and/or cover some portion of the reservoir with non-growing surface.  Either of those constitute additional costs.

One common question that comes up is whether swimming pools can be used as the reservoir for deep water culture.  The short answer is, sure they can.  The better question is, how cost effective will they be?  For a suburban family that wants to grow their own food in the backyard, which happens to be dominated by a pre-existing pool, that pool shape will determine how much they can grow.  If the pool is in a nice round, oval or rectangular shape, they can conceivably cover the vast majority of the pool surface with standard-sized rafts.  The little bit of remaining exposed reservoir area could easily be covered with blank material, extra custom-shaped rafts, or left open to provide access for water quality testing, working with the rafts, etc.  However, if the pool is an odd shape, for instance teardrop or elbow shaped, that could become very difficult and tedious to work with.  At that point the growers would have to carefully consider their options and determine whether the crops are worth the extra cost and hassle.

Do It Yourself Potential

At hobbyist and micro-commercial production scales, deep water culture is very much in the DIY realm.  Any container that will hold water can serve as the nutrient solution (although you may want to stay away from metal containers, because that can skew nutrient balances).  Rigid Styrofoam insulation boards will serve very nicely as rafts.  Net pots, fiber pots or seedling plugs can all be used to hold the young plants from germination through maturity.  With those smaller scales of operation, DWC is perhaps the premier DIY hydroponic method.

One of the more common approaches to DIY deep water cultivation, is to use either buckets or small tubs for the reservoirs.  This approach can be used very inexpensively to test the basic system method, before investing large amounts of time, money or energy in larger scale operations.  This option can also be used with individual plants which would eventually become too large for a raft system.  While that latter situation may not be as cost effective as other approaches, it can help streamline an operation which already uses DWC, while expanding into larger crops such as tomatoes, squash and other top-heavy plants.  In this case, the lid of the container itself becomes the float, rather than relying on a styrofoam raft.

As the scale of operation gets larger, the DIY potential diminishes.  We’ve already discussed issues with reservoir construction and raft construction/materials for medium and large size operations.  A larger issue is that like anything else, production needs to be optimized at larger scales to offset larger scale costs such as nutrient solution heating/cooling, reservoir maintenance, etc.  Also, very large size operations will often make use of automation to not only move the rafts, but also continuously test the nutrient solution concentrations.  This is where the DIY potential drops off the map completely.  So for those folks who are determined to do things themselves, they’ll need to keep the scale relatively small.  How small is small?  I don’t have any hard numbers, but some extrapolation from systems I’ve seen handmade versus purchased, predict that anything over 1000sqft of growing space is more effectively purchased than built.  If growers out there have larger DIY systems, Contact Us with those details and we’ll feature your operation! 

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