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permaculture - Re: [permaculture] [compost_tea] Dispensing tea - spray or dribble?

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  • From: venaurafarm <venaurafarm@bellsouth.net>
  • To: compost_tea@yahoogroups.com, permaculture <permaculture@lists.ibiblio.org>, Market Farming <marketfarming@lists.ibiblio.org>
  • Subject: Re: [permaculture] [compost_tea] Dispensing tea - spray or dribble?
  • Date: Sat, 30 Mar 2013 18:02:36 -0400


On 3/28/2013 5:22 PM, bberryvp wrote:
I plan to apply bacterial tea to some pasture I am trying to improve.
I will probably make a dispenser for my tractor, since about 10 ft
wide is all I need. Rather than spray, one thought is to basically
dribble the tea out of a manifold, with holes closely spaced such as
1/2 inch apart. I can solve issues such as manifold pressure
distribution to keep it pretty even. Since the tea is basically an
inoculant (as I understand it), could it be that dribbling might be
equal or better than spraying, since when spraying most of it will
not make contact with soil.
On 3/28/2013 9:41 PM, venaurafarm wrote:
If you don't intend to do foliar spraying then dripping it onto the
ground seems like a good idea, if you can control the distribution rate
without clogging the system. Will it be gravity flow or pressurized
lines? Beyond a certain point the microbes can be killed by being forced
with the tea through a system that uses too much pressure.
Here's a person who knows all about this and has designed and built a
large truck-mounted spray rig with sensors and controls to prevent over
pressurizing the lines: Frank Schultz

Frank sent me this reply:
<>

Yes, you are quite correct: Microbes are fragile and easily destroyed by impact or crushing.

General Notes -

1. Pumps - use only a diaphragm pump. The lower the speed, the better. Other types are very destructive. Centrifugals are the worst (giving you “bug purée”). Note that manufacturers of most diaphragm pumps specify a 50-mesh inlet screen to avoid clogging or blocking the valves. Large diaphragm trash pumps require no screen (they’ll accept chunks up to several inches) - however, their output pressures tend to be very low (a few feet of head).

2. Pressures - The lower the better. 25 psi max. The problem is de-compression. When suddenly released into the atmosphere at high pressures, the cell walls explode. I use nozzles rated for 15 psi min (for proper spray pattern) and try to stay close to this pressure (just a little over 1 Atmosphere [Atm.]). Do not use a pressure relief (pop-off) valve to regulate pressure - High velocities into right-angle turns!

3. Piping - To keep fluid velocities low, I use piping larger than what would normally be recommended for the flow rate. At turns, I try to use hose with wide, sweeping turns. If an elbow or tee is required, I adapt up to the next larger size, then reduce back down. If you’re using PVC piping, you can use Schedule 80 electrical (pulling) ells to also reduce the K-factor. Even though they are not pressure rated, I’ve had no problems up to 100 psi.

Please do not dismiss the many benefits of foliar application. While spraying is a completely different proposition from drip, foliar feeding can achieve the fastest response time from your plants - especially if there are disease issues or obvious nutritional problems. Also, since we field (broadcast) spray here, most (80%) of the spray mix goes on the ground - and most of the other 20% then runs off the leaves - onto the ground. Don’t limit yourself by thinking in terms of biology only. We recommend the addition of blackstrap molasses, humate, seaweed, micronutrients, trace elements and other things to the mix (depending upon the deficiencies found). These things are readily taken up through the leaves. Note: Don’t overdo the molasses - 1 quart/acre max.

With a few exceptions, anything sprayed has to pass a 50-mesh screen. We design soil fertility and crop nutrition programs for [generally large] growers all over the world. For irrigated growers, this involves a combination of spray and fertigation (through pivot or drip). In addition to biology, we always recommend some combination of nutrients. Some soil chemistries rapidly tie-up some of the nutrients - and in fact, the only way plants can get these nutrients for any length of time, is foliar. Accordingly, when a plant shows deficiencies in some of these (particularly the micros and traces) the surest and fastest way to correct these is with foliar. Be aware that many plant diseases are caused by nutritional deficiencies - especially in the micros/traces.

The really cool thing about irrigation is that you can continuously feed, giving your plants the nutrition they need (and only what they need) when they need it as their nutritional requirements change throughout the growing season. Performance and quality results can be truly dramatic. And - a nutritionally-balanced plant can require up to 70% less water(!) (per university studies) - And a healthy plant is subject to fewer disease and insect pressures!

With respect to your drip (“dribble”) plan: This involves a different set of problems. Commercial drip tape usually operates in the 8 - 10 psi range. The total opening presented by the micro-emitters is calculated for a maximum run length given the diameter of the tape to ensure consistent flow from each of the emitters over the entire length (same flow out of the first emitter through to the last). The electrical equivalent is presenting a number of very high-impedance (bridging) loads to a very low-impedance source. Tapes are usually ploughed-in at a depth of about 8”; however, some installations have it laying on the surface. Systems are designed to deliver about 9 gpm/acre - 24/7 in worst-case drought conditions. Tape emitters are extremely susceptible to plugging. Accordingly, manufacturers provide fairly elaborate filtration systems. The allowable particle size varies somewhat with the manufacturer but it is always quite small. Tape, especially buried, is subject to varmints. This problem has not been entirely resolved.

For some row crops and often in orchards, an above-ground round trunk drip line is sometimes used. Many installations have a large buried trunk line with risers and valves at intervals to which smaller, local lines are connected. With most all trellised crops (grapes, blueberries, hops, etc.), the trunk line is suspended from the trellis a few inches above the ground (but sometimes laying on the ground). With a manufacturer-supplied tool, holes are punched at desired intervals and small [micro] drip lines are inserted. These may be either open on the end or have emitters attached.

Flow through these open micro-drip lines is determined by pressure and length. The various emitters available have published flow rates. You may want to look carefully at these, however, as they may involve internal sharp right-angle turns to regulate flow. Also, some systems offer emitters that are pushed right in to the trunk line. These components are most readily available through Lowe’s or Home Depot - or other garden centers. The rated operating pressure is 10 psi, I think. And there are also many commercial systems available.

Again, consider trunk line diameter and length versus your flow requirements. The manufacturers have published tables to assist you in this.

Again, particle size is a consideration in these systems, so be prepared to have a strainer with the appropriate screen mesh installed. In the case of compost tea, you may want to have several strainers of progressively smaller mesh sizes. And again, if you use one of these systems, don’t use their pressure regulator!

There are several ways to non-destructively regulate pressure:

1. Control pump speed. This can be done electronically when a DC or a 3-phase AC pump motor is used. An expensive approach.

2. Maybe the best method is to have an overflow standpipe. At 0.433 psi per foot of head, this would be a pipe 23’ tall (for 10 psi static pressure - much under 1 Atm.) – returning to the tank. This might be the most practical for you. But whatever pressure is specified for the system, it must be constant. If use this approach, your pump must have the capacity to provide at least some overflow continuously - to maintain the static trunk line pressure.

3. A much less desirable method is to provide a bypass ball valve after the pump to return excess material to the tank. Not recommended – possible velocity and impact issues - and variable flow rates.

ABOVE ALL ELSE – Provide a washout fitting or valve at the end of each line! Sediments and growing things will accumulate in the system. You will have to periodically flush and clean (using bleach and/or Hydrogen Peroxide (32% - Beware!)) the system.

I suggest you make a trip to any of the above-mentioned stores and see what they have to offer – might give you some ideas. While there are several manufacturers of these systems, the one that comes immediately to mind is Rain Bird - but there are other good ones. For me, there is nothing like looking at the stuff in flesh and actually seeing how it all goes together…

AND – don’t overlook WATER QUALITY! With drought in many parts of the country resulting in falling aquifers, we’re seeing a dramatic rise in serious quality issues - mostly bicarbonates - sometimes Manganese and Iron - and sometimes salt. If your water is from a public utility, ask them for a water MINERAL analysis. If you’re using water from any other source, get an irrigation water test. Depending upon where you are, your water chemistry can be changing fast - even from a public utility. Depending upon your soil type and water, bad water can literally turn your soil to stone.

What’s in your water becomes part of your soil!™

Finally, we strongly, strongly recommend AGAINST using manure compost for teas. There is much more to compost, itself.

By the way, ACRESUSA published a book several years ago, titled, “Ask The Plant”. It is a very valuable resource.

Frank Schultz




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