The Role of Balanced Fertilization on the Reduction of Phytic Acid to Zinc Molar Ratio (PA/Zn) in the Irrigated and Rainfed Wheat Fields on the Calcareous Soils of Iran

Abstract

One of the most important quality factors in the wheat grain, which directly affects the quality of the bread, is the molar ratio of phytic acid to zinc (PA/ Zn) index. In order to evaluate the role of balanced fertilization on increasing the yield, quality, and reducing PA/Zn in wheat grain (Triticum aestivum L.), the first experiment was implemented with two fertilizer treatments (Farmer’s conventional fertilization practice, i.e. NP-fertilizers) and the optimum use of fertilizers (fertilization was on the basis of soil test results) in three different irrigated farms in Mianeh, East Azarbaijan province and the second experiment was carried out in 10 different dryland farms on the outskirts of the Khodabandeh, Zanjan Province in 2010-2011 growing season with an average of 380 mm annual rainfall. This experiment had three treatments, i.e. T1=Control (no fertilizer); T2=Farmer’s conventional fertilization practice (NP-fertilizers), and T3=Fertilization based on soil test values (Optimum use of fertilizers) in four replications with a randomized complete block design. The wheat cultivar in the irrigated farms was Alvand and in the rainfed farms was Azar-2. Protein, phytic acid, phosphorus (P), potassium (K), magnesium (Mg), iron (Fe), manganese (Mn), copper (Cu), and Zinc (Zn) in wheat grains were analyzed according to the standard methods. The collected data were analyzed by using a t-test and SAS Software. The results revealed that in the irrigated wheat fields, the optimal use of fertilizers increased the grain yield up to 27 percent, protein content, all micronutrients especially Zn significantly, but it decreased PA/Zn molar ratio significantly in comparison to Farmer’s conventional fertilization practice. While phytic acid concentration in the control plots was 8.70, it decreased up to 7.41gkg-1, Zn concentration was increased from 29 to 43 mgkg-1 and subsequently, PA/Zn molar ratio was reduced from 30 to 17. The statistical analysis showed a significant difference for phytic acid, Zn, and PA/Zn molar ratio in all wheat farms in the second experiment, the results demonstrated that while the average grain yield in T1 was 975kgha-1, it has increased up to 1401kgha-1 in T2 and over 1628kgha-1, respectively. The average yield increase was significant at the 5% level despite the existing drought situation in the fall of 2010. The mean concentration of P and Zn in wheat grains in the control plots were 0.26 percent and 21mgkg-1, in Farmer’s conventional fertilization practice were 0.24 percent and 25mgkg-1 and in the fertilization based on soil test values were 0.21 percent and 30mgkg-1, respectively and they were significant in the 5% level. While PA/Zn in the control plots was 29, it has been decreased to 22 in T2 and to 15 in T3 plots, respectively. Comparison between PA/Zn molar ratios revealed that due to the existing water during the growing season in the irrigated fields, the availability of all nutrients including Zn was slightly higher, but in drylands, the amount and distribution of rainfall is much important and it is clear that by increasing the amount and distribution of rainfall during the growing season, more grain yield and lower PA/Zn molar ratio is expected. It is obvious that these variations are widely dependent on climate change, cultivars, and management factors. This project is recommended to be continued at least in the wheat-grown provinces all over the Iran.