|Keywords (Extracted from title, table of contents and
abstract of thesis)|
Allelopathic, Potential, Sunflower,
germination, Residual, Activity, Proceeding, pea, Crops, pulses,
Rice, Wheat, Maize and Pea are four major economic crops of the world. Rice is second largest crop, which feeds more people than any other single plant species. Wheat satisfies the nutritional requirements of the world's population whereas maize is used as fodder, oil source and for nutritional purpose. Similarly pea represents about 40% of worlds trading in pulses. Average yield of all these crops is very low in Pakistan as compared to world. In present studies the possible role of sunflower allelopathy in decreasing the economic produce of test crops was evaluated during germination and field trials. For this purpose, during germination and early growth bioassays, four varieties of each, rice (B.Pak, B.Super, B.385 and IRRI Fine), wheat (Inqlab 91, Punjab 96, MH 97 and Pasban), maize (Golden, Sultan, A-97 and EV. 6089) and pea (Local Meteor, Archal India, Meteor Royal Swiss and Green Cross) were subjected to different concentration viz. 5, 10 and 15% of fresh and dry root, stem and leaf aqueous extracts of sunflower variety Hysun 33. Leaf extracts especially in higher concentrations, followed by stem and root, significantly inhibited the percent germination and early growth of all test crop varieties. During field trials sunflower was grown to maturity twice a year (spring and autumn) and was then mixed into the soil in field plots to be used for the cultivation of rice, wheat, maize and pea crop immediately after sunflower mulching (class A) and after harvesting the crops of class A (class B), under different treatments. In both the classes the growth of these crops was inhibited significantly under sunflower mulching and similarly increased in NPK treatment while effect was intermediary in NPK+sunflower mulched condition in comparison to control. Mycorrhizal colonization in all the test crops decreased significantly in sunflower mulching and NPK treatment as compared to control with transitional results under NPK+sunflower treatment at three growth phases. Seven allelochemicals viz. p-coumaric acid, vanillic acid, syringic acid, ferulic acid, cinnamic acid, p-hydroxybenzoic acid, caffeic acid were identified through thin layer chromatography in this sunflower variety. All the collected data was analysed statistically by Duncan's multiple range test and Analysis of variance. The results as have been discussed, concludes that residual sunflower allelopathy could be responsible for low produce of rice, wheat, maize and pea crop, grown in rotation with sunflower.