Weeds are a hidden foe for crop plants, interfering with their functions and suppressing their growth and development. Yield losses of ∼34% are caused by weeds among the major crops, which are grown worldwide. These yield losses are higher than the losses caused by other pests in the crops. Sustainable weed management is needed in the wake of a huge decline in crop outputs due to weed pressure. A diversity in weed management tools ensures sustainable weed control and reduces chances of herbicide resistance development in weeds. Allelopathy as a tool, can be importantly used to combat the challenges of environmental pollution and herbicide resistance development. This review article provides a recent update regarding the practical application of allelopathy for weed control in agricultural systems. Several studies elaborate on the significance of allelopathy for weed management. Rye, sorghum, rice, sunflower, rape seed, and wheat have been documented as important allelopathic crops. These crops express their allelopathic potential by releasing allelochemicals which not only suppress weeds, but also promote underground microbial activities. Crop cultivars with allelopathic potentials can be grown to suppress weeds under field conditions. Further, several types of allelopathic plants can be intercropped with other crops to smother weeds. The use of allelopathic cover crops and mulches can reduce weed pressure in field crops. Rotating a routine crop with an allelopathic crop for one season is another method of allelopathic weed control. Importantly, plant breeding can be explored to improve the allelopathic potential of crop cultivars. In conclusion, allelopathy can be utilized for suppressing weeds in field crops. Allelopathy has a pertinent significance for ecological, sustainable, and integrated weed management systems. Vijay Gopal More

Dear More,

Good day

Hope this paper can help you.

Reducing environmental pollution by chemical herbicides using natural plant derivatives – allelopathy effect...

There is good evidence that crop cultivar can influence weed growth. From example, work by Seavers & Wright demonstrated an allelopathic effect of oats on weeds in the UK. However, despite hundreds of small studies, mostly irrelevant because filter paper germination was used, no commercial scale allelopathy treatments have been developed anywhere, so far as I am aware.

please look this link https://pdfs.semanticscholar.org/2067/e3693e72a422649af2da373f59206c031abe.pdf

Allelopathic effect of Ocimum basilicum L. extracts on weeds and some crops and its possible use as new crude bio-herbicide

M. S., Mekkya; A. M. A., Hassaniena, * E. M. Kamela and A. E. A. Ismaila

a Weed Research Central Laboratory, Agricultural Research Center, Giza

9, El-Gamaa St. Giza, Egypt

Abstract

Experiments were carried out during 2018 and 2019 seasons, to investigate the allelopathic potentiality of Ocimum basilicum extract as a biodegradable herbicide against broad-leaved and grassy weeds. Leaves and flowers of Ocimum into flower were used to prepare extracts by three solvents (methanol, acetone and distilled water) to assay their effects on maize and soybean seedlings and dominant weeds in pots at Giza and fields Sids Stations. The inhibitor of 50% reduction (ID50) values on germination percentage for Amaranathus was about 0.2 to 0.9 mg, whereas for maize and soybean were 10 to 30 and 17 to 23 mg fresh weight of Ocimum equivalent extracts ml-1 respectively. Pots experiments showed that Amaranthus and Portulaca weeds were affected by extracts when applied post emergence which gave 33-68% reduction in fresh weight of Amaranthus/Portulaca mixture by the three studied extracts. Field experiment at Sids Station showed that the effect of different formulations, crude extract by acetone alone and extract plus camphor oil were more effective against broadleaved and grassy weeds than using its formulation with adjuvant where about 40.48 kg fresh weight of Ocimum equivalent extracts ml-1/hectare when applied post emergence gave 97 to 99% control of weed biomass, which equal the recommended herbicide (glufosinate ammonium) effect. The chemical compositions of extracts were analyzed by GC–MS to determine chemical compositons of the developing new bio-herbicide. Thus, the present results suggest clearly that farmers can use easily extract 40.48 kg/hectare of Ocimum to control weeds in horticulture orchard fields during summer season.

Keywords: Allelopathic; Bio-herbicide; Anatomical studies; ID50 studies; Ocimum basilicum L; Amaranthus spp.; Porulacae oleraceae; Xanthium sp., and sida alba and GC-MS analysis.

1. Introduction

Allelopathy is an important mechanism of plant interference mediated by the additional phytotoxins to the environment; chemicals with allelopathic potential are present in virtually all plants as in most tissues. Under appropriate conditions, these chemicals may be released into the environment, in sufficient quantities to affect neighboring plants (Tahir, 2011).

Weeds are unwanted plants, non-useful persistent, effectively competing with the beneficial and desirable plants for space, nutrients, sunlight and water (Mandel, 2000). Several researches were conducted on many of plant species such as (Acacia, Eucalyptus, Ocimum, Artemisia, Sweet potatoes and walnut) which produce allelochemicals that could be suppress the growth and germination of other crops and weeds growing near it (El-Khwas and Shehata 2005, Hassanein et al 2008, Janan et al., 2013, Mekky 2008, and Tahir, 2011). Allelopathy is a natural phenomenon of interference among organisms that may be employed for managing weeds, insects and diseases in field crops. The inhibitory effect was exhibited by all Ocimum extracts with maximum effects in leaf followed by root and seed extracts, which, caused the inhibition of germination, root and shoot elongation of maize and soybean, compared to the control. A significant effect on the germination velocity index of tomato seeds, as well as for lettuce and melissa root length and germination percentage with basil essential oil, (Rosado et al., 2009 and Verma et al 2012). The bioassays indicated that germination, root elongation and fresh weight of barnyardgrass were reduced by most of plant aromatic extracts. Sweet basil (Ocimum basilicum L.) and O. tenuiflorum, in the field emergence of barnyardgrass, common purslane and common lambsquarters were reduced by 11-50%, 26-79% and 58 - 83% in green manure-treatment of Ocimum basilicum plots, respectively, as compared with green manure-free plots (control). Otherwise, maize emergence was not affected by any green manure, (Dhima et al., 2009).

(Mominul and Hisashi, 2014) found that I50 values for shoot and root growth were ranged from 26 to 104 mg dry weight equivalent extract mL−1. Seedling growth was more sensitive to the extracts compared to seed germination, these phytotoxic plant could be used in several ways to control weeds, for example, (i) sowing/transplanting them as relay or cover crops with main crops, (ii) direct application of their crude extracts as bio-herbicides, or (iii) isolation and characterization of their active substances and using them as a tool for new natural and biodegradable herbicide development. Ocimum tenuiflorum L. Syn. O. sanctum is a widely distributed perennial shrub throughout the tropical and subtropical Asia. (Lawrence, 1998), found that O. tenuiflorum plant extracts have phytotoxic properties and thus contain phytotoxic substances, four essential oil chemotypes (methyl chavicol, linalool, methyl eugenol and methyl cinnamate) and also numerous subtypes of oils extracted from O. basilicum.

Please take a look at the following RG links.

Article Sunflower allelopathy for weed control in agriculture systems

Article Lily Cultivars Have Allelopathic Potential in Controlling Or...

Article Allelopathic stimulatory effects of wheat differing in ploid...

Article Sustainable weed management using allelopathic approach

Article Possible uses of allelopathy in weed control in organic farm...

Also see the following RG links.

Chapter Role of Allelopathy in Weed Management for Sustainable Agriculture

Chapter Rice Allelopathy for Weed Control

Chapter Wheat Allelopathy for Weed Control

Chapter Maize Allelopathy for Weed Control

Chapter Sorghum Allelopathy for Weed Control

sorghum bicolor

Article Allelopathy of weed extracts on yield and its components in ...

Please see my paper about allelopathy and week control in rice