Analysis and evaluation of available Zn, Mn, Cu and Fe contents of topsoil in Gulang Irrigation Region

Abstract: To provide a scientific basis for rational fertilization, the available Zn, Mn, Cu and Fe contents of top soils in 326 different sampling points that belonged to well irrigation areas, river irrigation areas and Yellow River irrigation areas were detected and analyzed from 2009 to 2010. The results showed that the available Zn contents in 81.6% of the well irrigation area soils, 67.1% of the river irrigation area soils and 41% of Yellow River irrigation area soils were lower than the critical value of the plant Zn demand, and this indicated the lacking of Zn was very serious in those regions. In river irrigation areas and Yellow River irrigation areas, the available soil Mn contents were 5.64-10.12, 6.46-14.68 and 7.22-15.17 mg/kg, respectively, which were higher than the critical value of the crop Mn demand(5.0 mg/kg), and the available soil Cu contents were 0.42-1.12,0.90-2.00,0.81-2.47 mg/kg respectively, which were also higher than the critical value of crop Cu demand(0.2 mg/kg). Therefore, the available soil Mn and Cu contents in those areas were at relatively high levels. Meanwhile, the available soil Fe in those three different kinds of irrigation areas were 2.88-8.08, 2.42-13.19 and 14.22 mg/kg, and the average values were 5.40, 10.20 and 12.30 mg/kg respectively. Although the available soil Fe contents in those areas were a little higher than the critical value of crop Fe demand (4.50 mg/kg), there were still 18.5% of the well irrigation area soils, 6.4% river irrigation area soils and 3.7% Yellow River irrigation area soils with low available soil Fe which did not reach the critical value of crop Fe demand. Generally speaking, available soil Zn were seriously lacking in those three irrigation areas, and available soil Mn and Cu contents were relatively high in most areas. Thus, those three irrigation areas needed Zn fertilizers and appropriate amounts of Fe fertilizers, and did not need Mn and Cu fertilizers, when crops were planted. Besides, the amount of fertilizer application should adapt to the crop species and the situations of soils.