عنوان مقاله [English]
In order to evaluate the role of mulch of cover crop (barley) in two systems of, seedbed preparation in autumn and in spring, on weed biomass and qualitative and quantitative yield of sugar beet, a strip split plot experiment based on randomized complete block design with four replications was conducted in Karaj (2012-13 & 2013-14). The treatments consisted of five different seedbed preparation and barley mulch including sole cropping in autumn (b1), barley mulch applied in furrow in autumn-sowing (b2) and both in furrow and hill (b3), sole cropping in spring (b4), and barley mulch applied in furrow in spring-sown sugar beet cropping. Individual plots included 8 rows with a length and width of 25 and 4 m, respectively. Each row was divided into three parts comprising sole cropping at the beginning (hand weeding, w1), weed infested control at the middle (no weed control over the growing season, w2), and chemical control at the end (using selective herbicides). Green and cover crop biomass in autumn seedbed preparation were immediately dried by Paraquat herbicide application and were incorporated to the soil, but for spring seedbed treatments, selective herbicide was used. The results of combined analysis traits showed that the competition of natural weeds of the field significantly affected root yield, sugar yield and white sugar yield. The reduction of more than 50% of root yield (32.12 t/ha), sugar yield (4.75 t/ha) and white sugar yield (3.63 t/ha) in the infested weed control treatment compared to the weed free showed a high potential damage of weeds in sugar beet fields. In the seedbed system in autumn, which sugar beet seed was drilled directly in spring, the addition of barley to become mulch reduced root yield by 13% in the fall row method and 19% in the fall method compared to the control treatment preparation of seed bed in autumn without barley (with root yield 57.55 t / ha). Considering no significant difference between sole cropping in spring (spring control) with low tillage of sole cropping in autumn (autumn control) for quantitive and qualitative yield of sugar beet suggests that by preparing the seedbed in the autumn, it is possible for early drilling sugar beet and make optimal use of the potential of the area.