Techniques- Throwing a Paddy

A paddy is a flooded field used for growing semi-aquatic crops like rice and taro. Controlled flooding allows efficient strategies for managing weed competition and fertility that are not possible in dry land cultivation. Cultures that use paddy based agriculture extensively are limited to regions with sufficient rainfall, flat enough land, or access to sufficient irrigation. In our subtropical seasonally dry climate and farm with mostly hilly topology there isn’t much opportunity for extensive paddy construction. The farm does however have some low gullies that are wet for about half the year so are potential sites for installing small paddies.

The first location I experimented with was a gully between two dams. The upper dam was the smallest on the farm with a very small rainfall catchment. This small dam has been very close to completely drying out during our worst droughts. As such I expected that any aquatic plants in this gully would potentially experience drought stress at times. Since I was unsure about how viable this new technique would be I invested a relatively small amount of energy and started small with just two paddy walls. I had also seen up to a foot deep of flood water rushing down this gully during storms so wondered if any structure I built could withstand the force. I made it at the top of the gully, the idea being the water had not yet gathered much momentum and was less likely to wash out the wall. To further reduce the force of the water I planted robust papyrus and cattails (Typha) in the upper paddy, leaving room for a trial of wetland taro in the lower paddy.

Using a hand sickle I cut the vegetation back and sliced along the edge of where I chose to cut across the gully. The shovel was then used to cut large cubes of mud that were lifted to the side to build the paddy wall, pressing them into place by stepping on the wall as it grew. The living vegetation was left uppermost to allow it to regrow rapidly and bind the wall together. As I worked I was intrigued to see abundant earthworms living underwater, presumably kept alive by the moving and oxygenated water. Mole crickets were also surprisingly common. As the wall grew the water started to gather behind it. I inserted some pipes a few inches from the top of the wall to allow water to overflow without eroding the wall, plus left the shoulders on either side of the wall lower than the middle to allow overflow during high rain events to go around the sides. I put up a chicken wire fence to keep out geese and later put a bird net over the taro to keep various water birds from disturbing the young plants.

As it settled in the system worked basically as expected. The walls quickly grew over with grass and weeds and withstood long periods of rain. The papyrus established as an effective buffer and stabiliser, though the Typha did not establish due to water birds pulling them out. The taro, despite consisting of several different varieties, did not establish or grow. It is possible none of them were wetland varieties and as such were doomed, so I may try again in the future if I can get a type that likes bogs. In general I have found water plants to be very particular about the depth and dynamics of the water around them, so if they are happy they explode with growth and if they are not they languish and vanish.

After the long drought I decided to repeat the technique recently. Another paddy wall was added below the first two, using the same mud block technique. It will be interesting to see how it stabilises as the rains come. I expect if we get a sudden downpour it may suffer damage before it has a chance to consolidate. I also experimented with extracting silt from the first paddies and transporting it to my vegetable garden on the top of the hill. Slowing erosion is one thing, while reversing it to restore soil fertility is a whole other level. This role as a silt trap to be used elsewhere is I suspect one of the most valuable functions of these structures, though time will tell how useful the material is as a soil amendment.

Further afield I have another wet gully that is an overflow between a dam and our creek. This area was originally choked with 2 m tall Setaria grass which I killed off with a couple of cycles of glyphosate. The Setaria was fairly restricted to the waterway, so spraying it off during a dry spell was quite manageable unlike other areas of many acres on the hills. The large clumps of grass would have been very damaging to remove by hand, both in terms of erosion and in terms of impact on my body. The risk of flooding also meant solarising with plastic wasn’t practical. The area was quickly revegetated with papyrus clumps, alternating with Typha that established strongly here, along with a wide variety of other native wetland species, transforming this space into valuable wildlife habitat. The papyrus and Typha also make valuable crafting material for me.

In this currently dry space I managed to install a large paddy wall at a natural narrow point which should help retain water for much longer through a large patch of Typha. I focused my digging on a small area a little upstream from the paddy wall. This allowed me to reach the deeper clay layers that form a more stable paddy wall. It also meant I created a concentrated deeper hole that will retain water for even longer during droughts for wildlife, and collect silt for use in nearby cropping spaces. Further upstream I installed two smaller such structures as well, though these are under a tree so the walls will likely not get covered in vegetation and may be less durable as a result. These three walls only took one morning to install. Across the farm there are probably a couple dozen other such structures I can build over time, but I will do so gradually, learning along the way. I suspect I lack sufficient paddy area to ever specialise in growing wetland rice and that taro will always be vulnerable to bird damage. Typha however is potentially very useful, producing starchy roots that can produce more starch per acre than any other crop, calculated at 2900 kg of flour per year per acre. At this optimum yield one persons’ entire annual energy requirement can be supplied by less than one tenth of an acre of cattails, which is around about the total potential area I have on the farm with all suitable places converted to paddies. The same small scale simple technology that will be set up for extracting Canna starch can be easily adapted for Typha, and their harvest seasons complement each other nicely. Typha also produces delicious edible pollen, edible tender flower shoots, leaves for weaving, and fluff for stuffing cushions. When I first planted it I was worried that it might “take over” the farm. Now I can’t find anything scary about having most of the wetter parts of the farm covered in this remarkable plant, and something as simple as a pile of mud formed by hand is enough to create its habitat.

My trial taro paddy, with the papyrus paddy in the background awaiting planting.
One year later the papyrus paddy is established and gave a crop of nice silt at least.
Paddy silt being applied to a veggie bed. Pushing soil uphill makes you appreciate the importance of preventing erosion in the first place.
A new paddy wall being constructed near my Typha stand, with the clay pit providing stable material.
The growing paddy wall coated in sticky clay.
A view of the Typha stand up stream from the clay pit.
A new paddy wall constructed down stream from the original taro test paddy.
Two small paddy walls with pits under the trees. Time will tell if they will erode without weed cover.
The goats inspect the clay pit filled with crystal clear rainwater overnight.

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