Allelopathy in Sustainable Use Systems
Definition; Allelopathy is the direct or indirect harmful or beneficial effect of one plant (through the release of chemical compounds, called allelochemicals) on the germination, growth, or development of other plants, and sometimes even on microorganisms.
Allelochemicals
- Produced in roots, leaves, stems, flowers, fruits, and residues.
- Released through:
- Root exudates
- Leaching from leaves
- Decomposition of plant residues
- Volatilization
Examples in Agriculture
- Sorghum & Pearl millet: Release sorgoleone, inhibiting weed seed germination.
- Sunflower: Residues suppress growth of succeeding crops and weeds.
- Rice: Some traditional varieties show allelopathic suppression of weeds.
- Sesamum & Brassica residues: Suppress soil-borne pathogens.
Applications in Sustainable Systems
- Weed Management; Use of allelopathic crops (sorghum, sunflower, rye, mustard) reduces dependence on synthetic herbicides. Crop residues act as natural mulch and weed suppressants.
- Pest and Disease Management; Certain allelochemicals reduce nematodes, fungi, and bacterial populations.
- Crop Rotations & Intercropping
- Sorghum → wheat rotation suppresses weeds in wheat.
- Mustard residue → controls root-rot pathogens in pulses.
- Cover Crops & Mulching; Cover crops like rye, vetch, or sesbania release allelochemicals and add organic matter.
Sustainability Link: Reduces agrochemical use, promotes ecological balance, and improves soil health.
Biomass Production in Sustainable Use Systems
Definition; Biomass in agriculture refers to the total organic matter produced by crops, trees, grasses, and residues, which can be used for soil fertility, energy, fodder, and industry.
Sources of Biomass
- Crop residues: Rice straw, wheat straw, sugarcane trash.
- Green manures: Sesbania, Dhaincha, Sunnhemp.
- Agroforestry trees: Gliricidia, Leucaena (Subabul), Sesbania grandiflora.
- Weeds and grasses: Lantana, Parthenium (after composting), Guinea grass.
Uses in Sustainable Agriculture
- Soil Fertility Improvement; Incorporation of crop residues adds organic carbon and nutrients. Green manures increase N availability and microbial activity.
- Bioenergy; Biomass can be converted into biogas, bioethanol, briquettes → reduces dependency on fossil fuels.
- Carbon Sequestration; Biomass acts as a carbon sink → important for climate change mitigation.
- Animal Feed & Bedding; Residues and grasses support livestock-based systems.
- Waste Utilization; Agricultural waste converted into compost/vermicompost → reduces pollution.
Integration of Allelopathy & Biomass for Sustainability
- Allelopathic cover crops (like rye, sorghum, mustard) → produce biomass + suppress weeds.
- Agroforestry systems → trees provide leaf litter (biomass) + allelopathic effects on weeds.
- Residue management → enhances soil organic matter and reduces need for herbicides.
- Reduced chemical dependency → supports sustainable and eco-friendly production.
Allelopathy
- Term “Allelopathy” was coined by Hans Molisch (1937).
- Sorgoleone (from sorghum roots) is a strong natural herbicide.
- Rice (traditional varieties) shows allelopathic weed suppression in paddy fields.
- Sunflower and eucalyptus residues have inhibitory effects on many crops.
- Mustard and brassica residues release isothiocyanates, which suppress soil-borne pathogens.
- Allelopathy is used in cover crops (e.g., rye, vetch, mustard) to reduce herbicide use.
- Helps in organic farming and low-input agriculture.
Biomass
- Biomass = total organic matter (crop residues, trees, grasses, green manures).
- India produces 500–550 million tonnes of crop residues annually.
- Green manures like Dhaincha, Sesbania, Sunnhemp add 40–80 kg N/ha to soil.
- Burning residues causes pollution – sustainable use is through mulching, composting, bioenergy.
- Biomass improves soil organic carbon, water holding capacity, and microbial activity.
- Biomass energy = bioethanol, biogas, briquettes, reducing fossil fuel dependency.
- Agroforestry trees (Leucaena, Gliricidia) are rich sources of sustainable biomass.
- Biomass contributes to carbon sequestration, helping mitigate climate change.
