Valencia orange trees [Citrus sinensis (L.) Osb.], budded on sour orange (C. aurantium) rootstock, were sprayed with four different potassium salts during 1995 and 1996. Twenty 5-year-old trees were sprayed once per month with one of the following material. K0: distilled water, K1: potassium green (a compound of different potassium salts, 35% K2O), K2: potassium nitrate (35% K2O), K3: potassium citrate (35% K2O), or K4: potassium sulfate (51% K2O). The vegetative growth occurred in three distinct successive cycles, i.e., spring, summer, and autumn. These cycles differed in time of commencement, duration and termination with respect to season. All potassium treatments significantly increased the shoot length and number of leaves/shoot for the three growth cycles. However, potassium green was superior overall other treatments. Percentage of leaf miner infestation was reduced at all potassium treatments. Potassium applications significantly increased leaf contents of N, P, K and decreased Ca and Mg levels.

The study was aimed to explore the phytotoxic potential of Sonchus oleraceus L. on the emergence and seedling growth of Echinocloa cruss-galli L. and quantification of allelochemicals present in leaves, stem and fruit of S. oleraceus weed. The experiment comprised of aqueous extracts of leaf, roots and fruits applied at 0.25, 0.5, 1, 2, 4 and 8% (w/v) along with a control (0%). Data regarding seed emergence, emergence index, emergence percentage, root length, shoot length and seedling dry weight was recorded. All the tested concentrations of all parts of S. oleraceus significantly inhibited the seed emergence, emergence index, emergence percentage (%) and growth and delayed mean emergence time and time taken to 50% emergence of E. cruss-galli weed. However, maximum mean emergence time (5.20 days) and time taken to 50% emergence (3.49 days), were noted at 8% concentration of fruit and leaf aqueous extract, respectively. Fruit aqueous extract at 8% concentration caused the lowest germination index (1.70), germination percentage (40%), root length (0.09 cm), shoot length (0.45 cm) and dry weight (0.16 g) of E. cruss-galli. Results suggested that the extract of S. oleraceus weed at concentration (8%) can be used as potential bio-herbicide for the control of E. cruss-galli weed.

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Chemical weed control method creates environmental hazards and residual effects in crops and soil. Alternate approach to control weeds is getting attentions in sustainable production system. Aqueous extract of crop is an important technique to control weed and also environment friendly and cheap. To investigate the herbicidal potential of aqueous extract of winter crop Carthamus tinctorius (safflower) on summer weed Oryza punctata (red rice) seed germination and initial seedling growth, a study was planned in Weed Science Laboratory. In this study, seeds of C. tinctorius were incubated in seven concentrations (0, 0.25, 0.50, 1, 2, 4, and 8%) of different parts i.e. leaves, stem, flower of C. tinctorius. All the tested concentrations of various plant parts of C. tinctorius significantly inhibited the mean emergence time, germination index, germination percentage (%), time taken to 50% germination as well as growth of O. punctata weed. However, maximum mean emergence time (4.73 days), time taken to 50% germination (4.19 days) was noted at 8% concentration and germination index of O. punctata was noted at 0.25% concentration when flower extract was applied. Leaf aqueous extract at the concentration 8% caused the lowest root length (1.53 cm), shoot length (4.51 cm) and fresh weight (54.72 g) of O. punctata. Results suggested leaf and flower extract of C. tinctorius at concentration (8%) can be used potential bio-herbicide for the control of red rice. Key words: Allelopathy, seedling growth, inhibitory, weed growth, plant parts, promotor