[permaculture] compost tea, oxygen & molasses

Robyn Francis robyn at permaculture.com.au
Wed Jun 3 22:41:43 EDT 2015

I didn’t notice a clear answer to the original question about DO levels in compost tea - thread got a bit off topic...

To keep the tea aerobic, the oxygen level needs to be 5.5 ppm. Ask in an aquarium shop and they’ll show which air pumps will do the job for the quantity you’re making. We generally do 20 - 40 Litre (5-10 gal) batches so our pump can provide 5.5 ppm for up to 40 litres. We don’t use an aerating stone (they get blocked and reduce the O2 flow), just have the air tube weighted down to bubble from the bottom of the container.  

SFW recommend that you don't leave it for more than 3 hours without aeration, as it then becomes anaerobic, so that gives a guide for application time.

For vegetable crops and grasslands the molasses (or sugar) is important to feed the beneficial bacteria.  Molasses is not used in the fungal-dominated compost teas made for tree-based systems. 

This is the compost tea recipe we make here:
40 liters water (10 gal)

60ml (2 Tblsp) humic acid – diluted in 1 cup water

120ml (4) Tblsp kelp extract – diluted in 1 cup water

2 Tblsp molasses (or dark brown sugar. NB do not use honey) - dissolved into 1 cup water

Add the above to the water and commence aeration, the suspend the bag or stocking holding the compost/worm castings:

500ml  (2 cups) container of compost

500ml  (2 cups) container of worm casting

1 cup of probiotic liquid (whey of yogurt, kefir or curd cheese; kambucha; liquid from sauerkraut or kimchee) 

Aerate for 24-30 hours. In cool weather it might need to brew for 2-3 days.

Sometimes we check the brew under the microscope and do a count of what’s in there (bacteria, amoeba, fungi etc)


> On 20 May 2015, at 5:20 pm, Steve Hart <stevenlawrencehart at gmail.com> wrote:
>> The compost tea discussion in question involved exploring ways to keep
>> AACT,
>> aerobically activated compost tea, aerobic through the time of field
>> application.
>> Court mentioned a study done that showed flowforms oxygenated liquids
>> flowing through them.

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