Plants release chemicals to their environment on an ongoing basis. Some chemicals have a positive effect and aid in plant growth. Others chemicals could have a negative effect. Autotoxicity is the phenomenon where a plant releases chemicals (called allelochemicals) that have a negative effect on the surrounding plants. The plant releases the allelochemicals as a defense mechanism, due to stress conditions like temperature, drought, UV light etc.
Autotoxicity in some crops causes stunted growth and ultimately death of the crop. Some of the commercially available crops that have been studied to ascertain this phenomenon are cucumber, strawberry, and bean. These studies indicate that hydroponics yield better results in the elimination of toxins.
Hydroponics and autotoxicity:
In soil media, even if parameters such as temperature, humidity or pests are controlled, the soil itself could trigger autotoxicity through root exudates. Thus it is nearly impossible to eliminate all stress factors and hence mitigation of autotoxicity is difficult.
In a hydroponics system, most of the parameters are highly controlled and monitored. This minimizes the difficulties associated with autotoxicity. Hydroponics systems make use of liquid nutrient solutions both in NFT and DWC. These nutrients also aid in the removal of allelochemicals and thus improve plant growth and yield.
In strawberry, for example, the root exudes chemicals such as benzoic acid, lactic acid, succinic acid, adipic acid, and p-hydroxybenzoic acid. These can stunt the growth of shoot and root.
Control measures found effective for in the hydroponic cultivation of strawberry:
- Activated charcoal – Addition of activated charcoal absorbs the autotoxic chemicals.
- Synthetic phytohormones like NAA (1-Naphthaleneacetic acid, 5.4mM) were most effective in treating autotoxicity.
- Adding 2,4-D (2,4-Dichloroacetic acid) which, when added to the nutrient medium, can have positive growth on plants.
Other important considerations:
- Addition of microbial strains to the nutrient solution, at reproductive growth stages of cucumber, reduces toxicity.
- Consider adding water-soluble amino acids at about 2ml/plant, three times a week.
Keep enjoying the benefits of hydroponics!