Introduction: Nowadays, with the growing global population, the sustainable production of agricultural products to feed humans is one of the ministerial problems that cause researchers to find solutions to increase crop products by increasing the cultivated area and yield per unit area. Under high soil pH absorbing nutrients through the roots is undesirable. Thus, it is essential to use foliar application and foliar absorption of nutrients in providing nutrients needed by plants. Iron is one of the low-use essential elements for the growth of plants, and generally, the amount of this element in the soil is high. But some chemical and physical properties of soils, such as the lack of organic matter, and alkaline pH, prevent the absorption of iron by the plant. This research aims to investigate the effect of iron foliar application on grain maize cultivars' quantitative and qualitative yield.
Material and Methods: This experiment was conducted in the agricultural year of 2015 in the educational-research farm of the Agricultural Research Institute of Zabol University in a factorial design in the form of a basic design of random complete blocks with 3 replications. Maize cultivars in four levels including (Single Cross 704, Limagrain LG 36.07, Iranian Maxima and Hungarian Maxima) as the first factor and the foliar application of the micronutrient iron sulfate in concentrations (control, 3 and 6 gr.lit^-1) as the second factor was performed the six-leaf stage and before flowering. Each experimental plot had four planting rows with a distance of 40 cm, the distance between the planting rows was 15 cm, and the length of the planting line was 4 meters. Analysis of variance data was done with SAS software version 9.1 and comparison of means was done using Duncan's test at the 5% level.
Results and Discussion: The results of the means comparison showed that the highest seed yield (4251.6 kg ha^-1) was obtained from the Limagrain cultivar under foliar application of 6 g lit^-1 iron sulfate showed an increase of 49.13% compared to the lowest value. Considering the role of the iron element in the enzymes involved in the photosynthetic process of the plant, it can be said that the foliar application of iron sulfate at a concentration of 6 g lit^-1 has improved the photosynthetic activity of the plant and by increasing the access of the reproductive organs of the plant to the photosynthetic materials, the weight of one thousand seeds and the length of the cob (the number of seeds formed in the row) and finally the grain yield increased. Also, the results showed that the seed nitrogen and protein percentage was the highest in the Limagrin cultivar (1.4% and 8.75%, respectively). Also, the seed nitrogen and protein percentage increased under foliar application by 6 g lit^-1 iron sulfate (1.33% and 8.31%, respectively). The seed nitrogen percentage increased by 9.02%, and the seed protein percentage showed an increase of 8.9% compared to the control treatment. Based on the results of this research, it was found that foliar application of iron sulfate significantly improved the protein of maize seeds compared to the control. Considering that the percentage of protein is related to nitrogen, thus iron sulfate foliar application showed a positive effect on both traits. It concluded that foliar application of iron sulfate has participated in protein production in maize plants.
Conclusion: Considering that many of the soils of arid and semi-arid regions have calcareous characteristics and alkaline reactions, foliar application of the micronutrient element iron during the vegetative growth stage can cause the absorption of other nutrients, growth of meristem tissues, increase in greenness and photosynthesis of leaves and finally cause increase performance. The results of the present experiment showed that using the foliar application and foliar absorption is necessary for providing iron micronutrient elements. As a result, foliar application of iron sulfate on maize plants can compensate for the lack of this essential element in the soil of dry areas. Based on the obtained results, it was determined that the use of the Limagreen cultivar under foliar application of 6 g lit^-1 iron sulfate can produce a good yield in the Sistan region.