Some gardeners swear by it. Others are not so sure. Heba A K Ibrahim from the Desert Research Center in Egypt argues that compost tea is a crop’s best friend.
Compost tea is deﬁned as ﬁltered product of compost (Litterick et al. 2004) steeped in any solvent, usually water, for more than an hour (NOSB 2004).
The two basic methods for production are anaerobic, or aerobic, and there’s research to support both approaches. The aerobic method ‘brews’ beneficial bacteria with added oxygen, introduced by something like an aquarium pump. This creates an environment that favours bacteria that require oxygen (aerated compost tea, ACT). Anaerobic is the opposite – you put the lid on, and keep the air out.
View to a brew
It can be made with or without additives, some of which may stimulate microbial biomass during the brewing time (Lanthier 2007 and Naidu et al. 2010).
Due to the aqueous nature of compost tea, microbial biomass, soluble nutrient components and fine particulate organic matter can be applied to soils and plant surfaces in ways not possible with solid compost (Hargreaves et al. 2009).
Compost tea is an agricultural tool, when produced with microbiological quality, and integrated into managed biological farming systems. It can be used as a carrier to deliver plant nutrients and manage plant diseases (Scheuerell 2004)
Rich in soluble mineral nutrients, compost tea delivers beneficial organic compounds and contains a high population of microorganisms. It can be used to fertilize crops, helps a plant’s leaves to absorb nutrients and assists a plant’s root system to extract nutrients from the soil.
Another benefit of compost tea is that it can also inoculate crop residue, which facilitates decomposition, resulting in improved nutrient cycling in soil by increasing microorganism activity.
It can help manage certain plant pathogens through microbial competition and build soil structure when applied as a drench (Shrestha et al., 2011a, b and Pane et al. 2012).
Air-and soil-borne plant pathogens can be suppressed by the plant growth promoting rhizosphere (PGPR) microorganisms found in compost tea.
Suppression effects work in a several ways; compost tea competes with pathogens for nutrients, covers surface area (which prevents pathogen gaining access) and it secretes secondary metabolites (antibiotics) against plant pathogens (Scheuerell and Mahaffee 2004)
The presence of beneficial microorganisms and chemical inhibitors such as phenols and amino acids in compost teas make it a natural diseases inhibitor (Siddiqui et al. 2008).
In addition, antibiotics that can accumulate in compost teas during production enhance plant defense responses (Scheuerell 2003).
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Hargreaves J C, Adl M S and Warman P R (2009). Are compost teas an effective nutrient amendment in the cultivation of strawberries? Soil and plant tissue effects. J. Sci. Food Agric., 89: 390-397
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Scheuerell S J and Mahaffee W F (2004). Compost tea as a container medium drench for suppressing seedling damping-off caused by Pythium ultimum. Phytopathology, 94:1156-1163
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