No abstract

No abstract

No abstract

The velvetleaf is an important annual weed in the Mazandaran province, Iran. Seeds are the only way of propagation and renewal of this weed. More knowledge was gained regarding soil seed bank and its seed production to improve the management of the velvetleaf weed in the future. There is a minimal information concerning the impact of the soybean planting pattern on the dynamics of the velvetleaf population. For this reason two different fields have been studied with the cooperation of the Agriculture Discipline of the Islamic Azad University, in Qaemshahr, Iran, during 2009 and 2012. In this study the effect of two types of soybean row spacing were used, 50 cm-wide and 36 cm-narrow, and three emergences of the velvetleaf weed population (periods 0-10, 10-20 and 20-30 days after soybean sowing were implemented) were studied. Seed production, leaf area and dry matter increased in each plant population of the velvetleaf weed in the 50-cm soybean rows. Mortality rates were decreased in velvetleaf's seedling population in the wider spaced rows. By observation it was seen an increased production of seeds in the first batch of seedlings. It appears that we must remove the first weed emergence flushes within three to four weeks after the soybean emergence to prevent reduced yields in the soybean crop and further increase of the velvetleaf seed bank.

Cover crops influence on canopy structure and light interception of maize (Zea mays L.) and velvetleaf (Abutilon theophrasti Medik), was studied in a field experiment. Treatments included planting of bean (Phaseolus vulgaris L.), soybean (Glycine max (L.) Merr.) and berseem clover (Trifolium alexandrium L.) as cover crops at the same date and 21 days after maize. Sole cropping of maize under weed-free and weedy conditions were also included in this experiment. All tested cover crops significantly reduced leaf area density and height of velvetleaf up to 50 %, while maize leaf area density increased in the presence of cover crops. Among cover crops, bean and soybean were the most effective in reducing velvetleaf leaf area density and height. Bean and soybean also strongly reduced absorbed light by velvetleaf by up to 80 % compared to clover. Maize grain yields were significantly influenced by cover crops planting in the inter row space. Compared to weeds free plots, only treatment with soybean as a cover crop resulted in similar maize grain yields, while maize intercropping with bean and clover significantly reduced maize yields. Delayed planting of cover crops, 21 day after maize, increased maize grain yield compared to cover crops and maize planting at the same time. Obravnavanja so obsegala setev nizkega fižola (Phaseolus vulgaris L.), soje (Glycine max (L.) Merr.) in aleksandrijske detelje (Trifolium alexandrium L.) kot podsevkov, posejane istega dne kot koruza ali 21 dni po njeni setvi. V poskus sta bili vključeni tudi 2 kontroli (čista setev koruze z zatiranjem in brez zatiranja plevelov). Vsi preizkušeni podsevki so značilno zmanjšali gostoto listne površine in višino bržunastega osleza do 50 %, medtem ko se je gostota listne površine koruze v prisotnosti vseh treh podsevkov povečala. Med podsevki sta bila fižol in soja najbolj učinkovita v zmanjševanju gostote listne površine in višine bržunastega osleza. Fižol in soja sta v primerjavi z deteljo najmočneje zmanjšala absorbirano svetlobo bržunastega osleza, do 80 %. Podsevki v vrste med koruzo so značilno vplivali na pridelek njenega zrnja. V primerjavi s kontrolo brez plevela je samo obravnavanje s sojo kot podsevkom dalo podobne pridelke, podsevka fižola in detelje sta značilno zmanjšali pridelek zrnja koruze. Odložena setev podsevkov, 21 dni po setvi koruze, je povečala pridelek zrnja koruze v primerjavi z obravnavanji, ko so bili koruza in podsevki posejani istočasno.Ključne besede: zgradba sestoja, gostota listne površine, prestrezanje svetlobe, indeks listne površine, koruza, bržunasti oslez, tekmovalnost plevelov Zahra SHAKIBAFAR et al.

No abstract