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  • From: Barking Cat Farm <barkingcatfarm AT mindspring.com>
  • To: Market Farming <market-farming AT lists.ibiblio.org>
  • Subject: Re: [Market-farming] Drip irrigation/irrigation
  • Date: Thu, 3 Jun 2010 11:21:33 -0500

On Jun 2, 2010, at 11:44 PMJun/2/10, Chris Corbin wrote:
> Does anyone have any good resources ( books, websites) on how much to
> irrigate different vegetable crops. We have some crops under plastic with
> drip.

Hi Chris,

Don't have irrigation rates specific to crops, but I can tell you how we do
it and it has always worked for us. On all of our vegetable crops, we use
either in-line emitter pipe (such as shown on page 10 of this drip irrigation
supply company's catalog here
<http://www.dripworksusa.com/catalog/pg10-18.pdf>) or drip tape (such as
shown here <http://www.dripworksusa.com/store/ttape.php?left>). Here in
Zones 7&8, we try to put on 1 cubic inch of water on the crops each week,
maybe a bit more during the heat of the summer or if one or more of the crops
included in a particular irrigation zone is a heavy drinker.

Example: 100' long X 3' wide bed with two lines of drip tape
- 100' X 2 = 200' of drip tape;
- let's say we're using T1508HR, the first t-tape in the chart in that
catalog page;
- 200' of T1508HR puts out 40 gallons per hour (GPH) or .67 gallons per
minute (GPM) (they include a chart so you don't have to do the math);
- to get 1 cubic inch on 300 square feet (sf), we need 300 sf X (12 in X 12
in)/1 sf (to convert from sf to square inches (si)) = 4320 si;
- 4320 si X 1 inch (our desired amount of water/week) = 4320 cubic inches
(ci);
- from the unit conversion website
<http://www.onlineconversion.com/volume.htm>: 4,320 ci = 18.7 gallon [US,
liquid];
- to get 18.7 gallons (G) @ .67 GPM from the drip-tape, we'll need to water
18.7 G divided by 0.67 GPM = 27.9 minutes .

So we'll water that zone 30 minutes each week. There are a whole host of
natural variables that we've ignored here, including heat, soil tilth and
it's ability to retain moisture, etc., but this is a decent approximation
with which to start. You can do a similar exercise with the prefabbed PC
emitter pipe or with self installed emitters off of poly pipe. We happen to
use Dripworks, but of course there are many good drip irrigation suppliers
out there. If you ever decide to look at using anything from Dripworks,
contact them about wholesale pricing for professional farmers or growers.

Hope that helps some, will look forward to hearing from others on this,
Laurie
Barking Cat Farm



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