Influence of Tillage, Fertilizer, and Weed Management on Weed Seed Bank at Various Soil Depth of Wheat Production Field In Ethiopia

Screen house experiments were conducted on two soil types at two locations of central highlands of Ethiopia during 2002 / 2003 to determine the combined effects of tillage, fertilizer, and weed management on weed seed bank at various soil depths in bread wheat (Triticum aestivum L.) field. Among the dominant weeds identified in the soil seed bank and in the field, 89 % of the majority of the weeds were annuals and 11% of them were perennials and biennials. From the total weed species, only few were the most dominant species including Polygonum nepalense, Galinsoga parviflora, Plantago lanceolata, Gnaplium unions, Sonchus arvensis, Spergula arvensis, Anagalis arvensis, Commelina benghlensis, Corrigiola capensis from broad leaf weed species and Setaria spp., Bromus pectinatus, Snowdenia polystachya and Phalaris paradoxa from grass weed species. The results revealed that tillage, fertilizer and weed management systems had significant effects on weed seed bank. The weed seed bank distribution and seed bank size differed among tillage treatments. The total amount of weed density tended to increase more in no tillage than conventional tillage or moldboard plow at both locations. The highest number of seed density in 0-30 cm depth of soil was found in the Kuyu black soil followed by Holetta red soil. In the NT system a large amount of weed seed was found in the depth of 0-10 cm followed by CvT and MP. The densities of broad leaf and grass weed seed were higher in NT than in CvT or MP at both locations. The highest percentages of weed seed reduction across locations were recorded 80 and 62% on MP and CvT or NT respectively. Tank mixture of fenoxaprop-P-ethyl and fluroxypyr +MCPA resulted in a significant reduction ranged from 70 to 80% of total weed number followed by hand weeding twice at all locations. The interactions between tillage and soil depth and between soil depth and weed management were species specific. Significant interactions were resulted from Spergula arvensis,, Corrigiola capensis, Polygonum nepalance and Galinsoga prviflora weed seed bank size. More than 60% of broad leaf and grass weeds were suppressed by tillage. Weed management was more important