EFFECT OF PERIOD OF CULTIVATION ON THE ABUNDANCE AND DISTRIBUTION OF WEED SEEDS IN THE SOIL PROFILE

Abstract. An experiment was laid down in the greenhouse to determine the distribution of weed seeds at different soil depths and period of cultivation on the distribution of weed seed bank in the soil profile in Muzarabani. Soil samples from different depth levels (0-10, 10.1-20, 20.1-30 cm) were collected soon after harvesting from three different sites namely Gutsa, Mufudzi and Muringazuva of Muzarabani district. The soil samples were put in trays in the greenhouse and watered after every two days to field capacity. Weed seedlings were identified, counted, recorded and discarded for a period of 3 months. Soil samples were disturbed every week to allow more germination of dormant weeds. Depth (P=0.000) and site (P=0.005) had highly significant effects on the total number of weeds that emerged from the soil samples. The 0-10 cm of the soil had the highest weed seedlings that emerged. There was an equal weed seed distribution in the 10-20 cm and the 20-30 cm of the soil. Gutsa had the largest seed bank and there was no significant difference in seed bank size between Mufudzi and Muringazuva. Some weed species were site specific, Senna obtusifolia was only found in Muringazuva and absent in other sites. Eleusine indica was found in Mufudzi and was absent in other sites