Evaluation the Effect of Weed Management Strategies on Weed Seed Bank and Spinach Yield (Spinacia oleracea L.)

Document Type : Research Article


Ferdowsi University of Mashhad


Introduction: Spinach (Spinacia oleracea L.) is a quick-maturing, cool-season, hardy vegetable crop that is produced for both fresh markets (field packed in bunches or lightly processed in cellophane bags) and processing markets (frozen products). A fresh-market spinach can be grown in 30 to 50 days, while the same variety grown for freezer processing takes 70 to 120 days. Spinach require weed control from nearly the moment a gardener decides to plant them, extending throughout the growing season. Weeds are often the most serious threat for organic vegetable production. Therefore weed control is especially important at the early growth of them. Two recent trends in agriculture have encouraged to use alternative weed control methods instead of chemical control (Cordill and Grift, 2011). Soil solarization is a nonchemical method to control soilborne pests in which high temperatures produced by capturing the sun radiant energy. The method involves heating soil by covering it with a clear plastic tarp during a hot period of year when soil will receive the most direct sunlight. Another method is use of cover cops. Cover crop help to maintain soil organic matter, improve soil fertility, prevent erosion and assist in nutrient management. They can also contribute to weed management, increase water infiltration, and maintain populations of beneficial fungi. Therefore, this research was conducted to evaluate the effect of different weed management methods on the weed seed bank and growth characteristics and fresh weight of spinach based on principles of sustainable agriculture.
Materials and Methods: A field experiment was performed at the Agricultural Research Station Field of Ferdowsi University of Mashhad in growing season 2012-2013. Seven treatments including solarization using by dark and transparent sheets, three crop residues, sunflower (Helianthus annuss L.), barley (Hordeum vulgare L.) and garlic (Allium sativum L.), hand weeding and weed-infest control were arranged based on a randomized complete block design with three replications. Before the start of experiment, soil seed bank was sampled from the soil depth of 0-30 cm. Seed bank samples were conducted at two stages including before land preparation and after harvest times. Weed seed were pulled out from the soil depth of 0-20 cm and recognized by stereomicroscope. Yield of spinach was determined at the end of the growing season. Plant height, leaf area index (LAI), as well as dry and fresh weight were measured in five randomly selected plants. Data were subjected to the analysis of variance (ANOVA) using MSTAT-C. Significant difference among means were identified by Least Significant Difference (LSD) at the 0.05 level of significance..
Results and Discussion: In this experiment, the weed community of seed bank was comprised for 7 species. The results showed that solarization and use of cover crops significantly affected seed number of weeds on the seed bank (p≤0.01). The minimum and maximum relative density ranges were observed for amaranth (Amaranthus sp.) and barnyard grass (Echinochloa crus-galli L.) with 5.26-25.00 and 22.00-70.00%, respectively. Although decreasing of identified weed seed number affected by non-chemical treatments compared to control, but the highest rate of decrease (93%) was recorded in solarization with dark polyethylene. The impact of non-chemical management treatments was significant (p≤0.01) on growth characteristics and yield of spinach. The highest and the lowest fresh weight of spinach were observed for solarization with dark polyethylene (1921.3 g.m-2) and control plot (413.3 g.m-2), respectively. Application of garlic, barley and sunflower residues improved the fresh yield of spinach up to 41, 55 and 63% compared to control, respectively. These improvements were 75% and 78% for solarization with transparent polyethylene and hand weeding, respectively. Dark polyethylene enhanced growth characteristics and yield of spinach due to controlling of weeds, temperature regulating and improving moisture content of soil. Impact of solarization with dark sheets on seed bank, growth characteristics and yield of spinach was higher than transparent sheets. Crop residue application enhanced growth characteristics of spinach due to their positive effects on soil properties. So, based on the results of the present study solarization with dark and transparent sheets is an effective approach for weed control and improving growth characteristics of spinach.


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