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Germination of Major Weed Seeds in Response to Temperature and Nitrogen in Bench-Sheko Zone, South Western Ethiopia

Gedamnesh Muluneh, Mesert G Tsadik

Weed seeds and their germination requirements are very diverse. Integration of knowledge of weed germination and seed dormancy status could be used to improve weed control strategies. Weeds especially invasive weeds are a serious challenges causing low crop yield and food insecurity in Ethiopia. Understanding weed germination requirement and optimum temperature is essential to improve weed management practices. Consequently, as assistance in the improvement of control and management practices, the study was carried out with the objectives to: Determine optimum temperature in which major weed seeds germinate and to evaluate effect of nitrogen on germination of major weed seeds. The experiment was conducted at Mizan Tepi university bio medical science laboratory in Southern Ethiopia during 2020. Weed species, Amaranthus spinosus L., Commelina benghalensis L., Guzotia scabra Vis Chiov, Mimosa invisa L. and Parthenium hysterophorus L. which were infest crops in the study area were used in this investigation. Seeds of the weeds were exposed to five temperature regimes viz. 5°C/15°C, 10°C/20°C, 15°C/ 25°C, 20°C/ 30°C and 25°C/35°C for 16 hours followed by for 8 hours. Germination performance of the weed species was determined with and without nitrate (0 and 10 mM) solution. The weed was verified as germinated when the radicle or hypocotyl evidently projected over the seed coat. Weed seeds were punctured with a dissecting needle and placed on blotters moistened with 0.1% tetrazolium solution when they are recognized as ungerminated. The test was laid out in a completely randomized design in factorial arrangement with three replications. The result showed weed seeds germination percentage were affected significantly by alternating temperature, nitrate and their interaction. The highest weed seed germination was recorded at temperature range between 15/25°C-25/35°C with nitrate, but Mimosa invisa L. germinated regardless of nitrate. The highest germination (80.66% and 79.33%) was recorded in Parthenium hysterophorus L. at 15/25°C and 20/30°C with nitrate followed by (79.33%) in Guzotia scabra Vis Chiov at 20/30°C with nitrate. Mimosa invisa L. highest germination was recorded at 25/35°C. Amaranthus spinosus L. germination was highest at 20/30°C and 25/35°C with nitrate. Among weed species lowest germination was recorded in Commelina benghalensis L. Highest percentage of seed dormancy was recorded at lower temperature regardless of nitrate in all species. Among weed species highest dormancy more than 80% recorded in Amaranthus spinosus L. and Commelina benghalensis L. at 10/20°C and 5/15°C with and without nitrate. Except Mimosa invisa L. germination of all species pronounced at higher temperature with nitrate. Therefore the highest weed seed germination was recorded at temperature range between 15/25°C-25/35°C with nitrate which correlated with early spring to late summer temperature of bench sheko zone. It is suggested that applying different management option at their pick emergence period like stimulating weed seed to germinate in flash to reduce weed seed bank and adjusting nitrogen fertilizer application method like placing fertilizer close to crop seed and foliar application of fertilizer is important to reduce weed interference with crop productivity.