Investigating the effects of boron and zinc on corn seed set.

In some corn fields, in different parts of Iran, the phenomenon of partly grain- free ear is observed. This phenomenon can severely decreases corn yield. Although most researchers, mention that this phenomenon is the result of moisture and heat stresses at the time of pollination, but some other researches believed that it is due to the nutritional factors, especially Boron and Zinc nutritional elements. They believe that firstly, these two elements, especially Boron, affect on the moisture and heat stresses, and secondly both of them have a significant role in pollination process and pollen fertilization and therefore, deficiencies of these two elements could affect on corn grain production. In order to examine the effect of zinc and boron application on corn grain production, an experiment was conducted in corn fields of Fars, Khozestan (Dezful), Kermanshah, Karaj and ,Mazandaran during the 2003-2006. The experiment was factorial and conducted in the field as a Randomized Complete Block Design, with 20 treatments, replicated three times in each area under study. The treatments were composed of five level of zinc (O, 8, 16 and 24 kg.ha-1 in soil and foliar application of ZnSO4 with 0.5 percent concentration) and four levels of Boron (0, 20 and 40 kg.ha-1 of boric acid in soil and foliar application of boric acid with 0.3 percent concentration), and finally their means were compared. The results of statistical analysis in Fars area showed that, the individual and combination effect of B and Zn application on grain yield was significant at the levels of 1 and 5 percent probability respectively. On the other hand, the individual effect of Zn on ear weight, number of grain per ear, 1000- kernel weight, the Zn concentration, Zn total uptake and protein content of grains were significant at 1 percent level of probability. Application of B on total number of grain per ear, number of grain per length of ear and the concentration of zinc in grain was significant at 5 percent level of probability, but its effect on total and boron content was highly significant (ƒΡ ƒ­ 1%).The maximum yield of grain (10T.ha-1) was produced due to the application of 120 kg.ha-1 ZnSO4 with foliar application of Boric Acid The results of the experiment conducted in Dezful showed that, the effect of Zn on ear diameter, number of grins in ear length, leaf Mn content and concentration of N and K in grain was significant. On the whole, the statistical analysis of 3 years experiment revealed that, application of 40 kg. ha-1 ZnSO4 produced the highest yield of grain up to 7610 hg.ha-1. On the other hand, the main effect of B on leaf concentration of N, Zn and Fe, and grain content of P, K and Zn was significant, but was not significant on other characters. Among the B treatments, the foliar application produced the highest grain yield. The results of the experiments in Kermanshah showed that, application of zinc individually had only a significant effect on grain yield but without any significant effect on other parameters. At the some time, Boron had the same effect on grain yield and other parameters. The soil application of 120 kg.ha-1 ZnSO4 and foliar application of Boric Acid produced the highest yield (equal to 9227 kg.ha-1) and compared with control plot (8529 kg.ha-1) it rises the yield up to 700 kg.ha-1. The maximum protein content of grains was obtained by application of 50 kg.ha-1 ZnSO4 and 40 kg.ha-1 Boric Acid. The results of Karaj experiment showed that individually application of zinc, had a significant effect on grain yield (ƒΡ = 1%) and on 1000-kernel weight (ƒΡ = 5%), but it had not significant effect on other parameters. At the same time, application of Boron individually and in combination with zinc had significant effect (ƒΡ = 5%) on grain yield, but had not any significant effect on other studied parameters. The highest grain yield (with 14% moisture content) was obtained through the application of 40 kg.ha-1 ZnSO4 and 40 kg.ha-1 Boric Acid. This treatment increases the yield up to 35% with respect to control plot. The maximum 1000- kernel weight (equal to 327g) was obtained due to the application of 80 kg.ha-1 ZnSO4 and 40 kg.ha-1 Boric Acid but had not significant difference with other treatments. The result from Mazandaran experiment, showed that application of Boron caused a significant increased in grain yield (ƒΡ = 5%), but application of zinc individually or Zinc in combination with Boron, had not significant effect on grain yield. The maximum grain yield (10391 kg.ha-1) was obtained due to application of 120 kg. ha-1 ZnS04 and 40 kg. ha-1 Boric Acid, which produced more yield (1400 kg. ha-1). The application of Zinc individually had only a significant effect on the length of corn ear, but application of Zn + Born had significant effect on length and diameter of corn ear and their effect on other studied parameters was not significant. In general, based on the results of this experiment in different parts of the country, there was a positive and significant effect of Zn application on grain yield and an increase in Zn and protein content of grain; so that application of Zinc, on the average in 5 areas under study, caused 20% increase in grain yield. But, in 4 area of 5 area under study, the boron application, individually or in combination with zinc, although increases the yield with respect to the control plots, but the differences between different treatments were not statistically significant. Key words: Zinc, Boron, grain corn, seed set