Gardening with compost can be a tricky business. Consider the following:
Organic (Fermentation) Acids — Organic acids occur in compost that is immature (not sufficiently decomposed) or that has been processed or stored under anaerobic conditions (fermentation), even for a short time.
Many organic acids are phytotoxic, often producing nearly immediate injury to plants that shows white or chlorotic (bleached) leaves. In composts with a high C:N ratio (>40:1), acetic acid is the primary organic acid formed (along with some alcohols). In composts with low C:N ratios, anaerobic conditions yield ammoniacal products (putrid odors) that cause the toxicity. A drop or increase in pH often is not a reliable indicator of the toxicity problem because these compounds decompose quickly (24 to 48 hr) after causing injury.
The first line of defense is to use mature compost. However, even mature compost products can develop organic acids if stored or shipped under anaerobic conditions (the likelihood decreases with maturity). Many organic acids have a sharp odor that signals their presence.
Tests that indicate maturity and bioassays can be used to detect the presence of organic acids also. However, in a relatively mature compost, the organic acids will decompose or dissipate if the sample is aerated. As a precaution, allow compost stored in piles or in a sealed truck to aerate for several days prior to use or sale. Also, inform customers about proper storage...
Many organic acids are phytotoxic, often producing nearly immediate injury to plants that shows white or chlorotic (bleached) leaves. In composts with a high C:N ratio (>40:1), acetic acid is the primary organic acid formed (along with some alcohols). In composts with low C:N ratios, anaerobic conditions yield ammoniacal products (putrid odors) that cause the toxicity. A drop or increase in pH often is not a reliable indicator of the toxicity problem because these compounds decompose quickly (24 to 48 hr) after causing injury.
The first line of defense is to use mature compost. However, even mature compost products can develop organic acids if stored or shipped under anaerobic conditions (the likelihood decreases with maturity). Many organic acids have a sharp odor that signals their presence.
Tests that indicate maturity and bioassays can be used to detect the presence of organic acids also. However, in a relatively mature compost, the organic acids will decompose or dissipate if the sample is aerated. As a precaution, allow compost stored in piles or in a sealed truck to aerate for several days prior to use or sale. Also, inform customers about proper storage...
