Allelopathic properties of compost: could we use a fertilizer as an herbicide for tree crops?

Soil management in tree cropping systems employs techniques like grassing, mulching, and weed control to improve soil health and reduce chemical herbicide use. Weeds compete with crops, leading to yield losses and increased reliance on synthetic herbicides, which pose environmental risks and contribute to the development of herbicide-resistant weeds. Sustainable alternatives like organic mulches, particularly municipal solid waste compost, can enhance soil structure, fertility, and weed suppression, promoting sustainable agriculture. In this opinion paper, we focused on the antigerminative effects of compost, which can inhibit seed germination and growth due to the presence of allelochemicals such as phenolic compounds, terpenoids, fatty acids, and ammonia. These compounds affect water uptake, hormonal pathways, and cellular functions. These antigerminative properties, though traditionally seen as negative for annual crops, offer potential benefits in tree cropping systems for natural weed control. Challenges include determining optimal application rates and addressing problems related to variable efficacy due to environmental conditions. Additionally, manipulating the composting process to produce specific amendments for different cropping systems could reduce reliance on synthetic herbicides, improve soil health, and decrease the risk of herbicide-resistant weeds. Bacteria like Pseudomonas and Bacillus play a key role in composting by degrading nitrogenous compounds, thereby influencing nitrogen cycling and promoting the formation of nitrogenous compounds that may inhibit weed growth. Fungi such as Alternaria alternata, that may survive during the mesophilic composting phase as spores, produces phytotoxic tentoxin, which could be harnessed for bioherbicidal use. These processes are essential in compost maturity and plant growth impact. Further research is necessary to optimize compost applications for weed control and develop practical guidelines for its use.