Effects of Green Manure and Mixed Culture of Maize (Zea mays L.) and Canola (Brassica napus L.) on Bioavailability and Uptake of Iron in Greenhouse

Iron is one of the essential micronutrients for plants. Despite sufficiency of total iron in soil، there is Fe deficiency in most soils. Changing of soil chemical properties is one of the effective manners to improve the Fe nutrition in plants. To investigate the effects of alfalfa green manure and mixed culture of maize and canola on some chemical properties of rhizosphere and bioavailability and uptake of iron، a greenhouse experiment was conducted using rhizobox systems in a factorial design، with 3 replications، two levels of green manure (0 and 2% w/w) and 4 cropping treatments (maize alone، canola alone، mixed maize and canola، and control). Results showed that the green manure addition reduced pH but increased dissolved organic carbon concentration (DOC) and soil organic matter (SOM) and thereby increased bioavailability of iron by more than 4 mg/kg of soil. Green manure addition also enhanced shoot dry weight and increased uptake of iron in canola shoot by 54 µg/kg soil. Results of simple correlation coefficient showed a dynamic relationship between increase in iron bioavailability in the rhizosphere and pH reduction and increase in DOC، SOM، and EC. The results of plant analysisshowed that green manure addition reduced concentration of iron in shoot of the mixed culture. Intercropping of maize and canola increased plant dry weight 4. 4 g per pot more than canola and 5. 5 g per pot more than maize in single culture. Therefore، green manure addition and mixed culture system were useful in increasing yield. Also، intercropping of maize and canola was effective in increasing iron in maize shoot.