Summary The importance, characteristics, positive and negative impacts, and future role of weeds as an integral part of the natural and agroecosystems are evaluated and discussed. Interference between plants in nature and the importance of differentiating between competition and allelopathy are interpreted. Allelopathy as one component of weed/crop interference, allelochemicals from weed species and their possible mechanism of action are listed and discussed. Weed species with inhibitory action against cultivated crops, other weed species, and plant pathogens, as well as self-inhibitory (autopathic) species are reviewed. Stimulatory or inhibitory allelopathic effects of different crop plants, trapping and catching species, and the potential of allelopathic weeds in inhibiting or stimulating certain parasitic weed species are discussed and evaluated. Allelopathy as a mechanism and future strategy for agricultural pest control and farm management and the potential use and development of some allelochemicals...

Weed allelopathy, its ecological impacts and future prospects: a review

Allelopathic effect of black mustard (brassica nigra l.) on germination and growth of wild oat (avena fatua l.)

Phytotoxic effects of Lantana camara, Eucalyptus camaldulensis and Eriocephalus africanus essential oils in weeds of Mediterranean summer crops

History.- Historical Examples of Allelopathy and Ethnobotany from the Mediterranean Region.- Allelopathy: Advances, Challenges and Opportunities.- Allelopathy in Chinese Ancient and Modern Agriculture.- Allelochemicals and Allelopathic Mechanisms.- Allelochemicals in Plants.- Allelopathy: Full Circle from Phytotoxicity to Mechanisms of Resistance.- Allelopathic Mechanisms and Experimental Methodology.- Indirect Effects of Phenolics on Plant Performance by Altering Nitrogen Cycling: Another Mechanism of Plant-Plant Negative Interactions.- Genomic Approaches to Understanding Allelochemical Effects on Plants.- Allelopathy from a Mathematical Modeling Perspective.- Application of Allelopathy in Agriculture and Forestry.- Progress and Prospect of Rice Allelopathy Research.- Rice Allelopathy Research in China.- Recent Advances in Wheat Allelopathy.- Sorghum Allelopathy for Weed Management in Wheat.- Allelochemicals in Pre-cowing Soils of Continuous Soybean Cropping and Their Autointoxication.- Autotoxicity in Agriculture and Forestry.- Black Walnut Allelopathy: Implications for Intercropping.- Plant Growth Promoting Rhizobacteria and Mycorrhizal Fungi in Sustainable Agriculture and Forestry.- Utilization of Stress Tolerant, Weed Suppressive Groundcovers for Low Maintenance Landscape Settings.- Allelopathy in Forested Ecosystems.

Allelopathy in sustainable agriculture and forestry

Increasing global population is a threat to food security and agricultural sustainability. Allelopathy has emerged as a pragmatic approach to solve multiple issues in modern agriculture. Multiple approaches including crop rotations, cover crops, intercropping, mulching, crop residue incorporation and water extracts application are being used to explore allelopathy for pest management, stress mitigation, and growth enhancement in crop production. Allelopathy offers natural control of weeds, insect-pests and diseases. Biosynthesis of secondary metabolites at higher rates and their role in stress signaling provides excellent defense against abiotic stresses. Allelochemicals exuded in plant rhizosphere improve nutrient acquisition through the processes of solublization, biological nitrification inhibition, chelation and selected retention. Allelochemicals promote growth at low concentration; however suppress the growth if applied at high concentration. Allelopathic water extracts of sorghum, brassica, sunflower, rice, wheat, maize and moringa improve crop growth when applied at low concentrations. In this manuscript, potential application of the allelopathic phenomenon in crop production is discussed. If wisely planned, use of this phenomenon is quite effective in managing agricultural pests and improving the productivity of agricultural systems.

Application of allelopathy in crop production

Allelopathic potential of Datura stramonium L.

Allelopathic effect of Blumea lacera L. on rice and common kharif weeds.

An experiment was conducted to find out grain yield, nitrogen concentration in the third leaf and nitrogen uptake by hybrid rice under different planting dates and nitrogen levels during 1999 and 2000. The hybrid rice planted on July 5 or 20 produced significantly higher nitrogen concentration in the third leaf, grain yield and nitrogen uptake by both grain and straw. The delayed planting between August 5 or 20 significantly reduced these crop parameters. The reduction in grain yield was to the extent of 14.06 and 28.23%, respectively compared with planting of July 5. Number of effective tillers, grains panicle-1, test weight, grain yield, N concentration in third leaf at different stages, nitrogen concentration and uptake by grain and straw increased significantly with increasing levels of nitrogen from 50 to 150 kg N ha-1. Highest R2 value has been observed for regression equation between N concentration in third leaf at 60 DAT and grain yield.

Effect of Planting dates and N levels on N concentration in the leaf, grain yield and N uptake by hybrid rice

Field experiment were conducted to study the performance of hybrid rice to scheduling of irrigation and nitrogen level. Nitrogen scheduling of 40+20+30+10 percent at basal, active tillering, panicle initiation and flowering reduced the sterility percentage and increased effective tillers and grain yield of hybrid rice. Irrigation, one day after disappearance of water proved as good as continuous submergence for yield components, grain yield and N content in stem and leaf at early stages, flag leaf, grain and straw. The irrigation schedule of one day after disappearance of ponded water required 604 mm less irrigation water than that of maintaining continuous submergence.

R. S. Tripathi

Papers

Allelopathic potential of Datura stramonium L.

Allelopathic effect of Blumea lacera L. on rice and common kharif weeds.

Effect of Planting dates and N levels on N concentration in the leaf, grain yield and N uptake by hybrid rice

Response of hybrid rice to scheduling of nitrogen and irrigation during dry season

Effect of planting time and nitrogen on tillering pattern, dry-matter accumulation and grain yield of hybrid rice (Oryza sativa)*