Hemmati E, Vazan S, Oveisi M
Department of Agronomy, Karaj Branch, Islamic Azad University, Karaj, Iran.
Commun Agric Appl Biol Sci. 2011;76(3):551-4.
Pre-planting irrigation and planting patterns are important factors in weed management that effect on seed bank. Additionally, the nitrogen is the most important factor in plant growth that affects weed-crop competition and ultimately, seed rain into the soil. A field experiment was conducted to study the effect of nitrogen application rates, pre-planting irrigation and maize planting patterns on weed seed bank population. Experimental factors were nitrogen rates at 4 levels (200, 300, 400 and 500 kg per hectare) as main plot; and pre-planting irrigation at 2 levels (irrigation before planting plus weeding emerged seedlings and, irrigation after sowing), and maize planting patterns (one-row and two-row planting of maize with same density per square of row length) that were assigned in a factorial arrangement to the sub plots. Soil samples were taken at the beginning of the season (before planting of maize) and at the end of the season (after harvest) at depth of 0-5 cm in the fixed quadrates (60 cm x 60 cm). The weed seeds were extracted from the soil samples and were identified using standard methods. The majority of weed seed bank populations included 6 weed species: Portulaca oleracea, Chenopodium album, Amaranthus retroflexus, Sorghum halepense, Daturea stramonium, Xanthium strumarium. Results showed that population of weed seed bank increased significantly with increasing nitrogen rate. The increasing rate was different between one-row and two-row planting patterns. The parameters indicated that seed bank population was much higher in a one row planting pattern of maize. With two-row planting, seed bank was decreased by 34, 26, 20 and 5% at 200, 300, 400 and 500 kg N/ha, respectively. Pre-planting irrigation was also found an effective implement to reduce the weed seed bank. When pre-planting irrigation was applied, seed bank was decreased by 57, 43, 34 and 9% at 200, 300, 400 and 500 kg N/ha. Increasing nitrogen because of weed's better growth and higher seed production neutralized the decreasing effect of pre-planting irrigation and two-row planting of maize on weed seed bank population.
种植前灌溉和种植模式是杂草管理中影响种子库的重要因素。此外，氮是植物生长中影响杂草与作物竞争并最终影响落入土壤的种子雨的最重要因素。进行了一项田间试验，以研究施氮量、种植前灌溉和玉米种植模式对杂草种子库数量的影响。试验因素包括：作为主区的4个施氮水平（每公顷200、300、400和500千克）；2个种植前灌溉水平（种植前灌溉并除草出土幼苗，以及播种后灌溉），以及以析因排列分配到副区的玉米种植模式（每单位行长密度相同的单行和双行玉米种植）。在固定样方（60厘米×60厘米）中，于季节开始时（玉米种植前）和季节结束时（收获后）采集0至5厘米深度的土壤样本。从土壤样本中提取杂草种子，并使用标准方法进行鉴定。杂草种子库数量的大部分包括6种杂草：马齿苋、藜、反枝苋、石茅、曼陀罗、苍耳。结果表明，随着施氮量的增加，杂草种子库数量显著增加。单行和双行种植模式下的增加速率不同。参数表明，玉米单行种植模式下的种子库数量要高得多。采用双行种植时，在施氮量为200、300、400和500千克/公顷时，种子库分别减少了34%、26%、20%和5%。还发现种植前灌溉是减少杂草种子库的有效措施。当采用种植前灌溉时，在施氮量为200、300、400和500千克/公顷时，种子库分别减少了57%、43%、34%和9%。由于杂草生长更好和种子产量更高，施氮量增加抵消了种植前灌溉和玉米双行种植对杂草种子库数量的减少作用。
