Study On Distribution Of Available Microelements In Soils From Gannan Navel Orange Orchards

Microelements of plant are mainly derived from soils, and the lack of microelements in soil could make plant poor growth and reduce productivity. However, the redundant of microelements in soil could also affect the crop yield and quality. The main factors influencing the content of microelements in soils include soil parent material, organic matter, p H, and human activities.Gannan district, in southern Jiangxi Province, China, is one of the world’s largest navel orange planting bases. Results of the distribution of available microelements in soils are helpful for reasonable application of microelement fertilizer, the formulation of strategic sustainable agriculture in Ganzhou navel orchards and improvement of the navel orange yield and quality.In this study, a total of 1405 soil samples were collected from 477 representative navel orchards throughout the 18 counties in Gannan. The contents of available copper, available zinc,available iron, available manganese and available boron were analyzed, and the relationships between the content of microelements and the soil type, the orchard age, p H and organic matter in soil were investigated. The results were as follows:1. The mean available contents in navel orange orchard soils for copper, zinc, iron,manganese and boron were 1.55 mg·kg-1, 2.85 mg·kg-1, 83.57mg·kg-1, 63.37mg·kg-1, 0.16mg·kg-1,respectively. Available Cu of 76.45%, available Mn of 85.55% and available Zn of 75.16% in orchard soils were in a moderate level, and available Fe of 98.58% were in a high level. However,the orchard soils in a moderate level for available B were only 14.3%, which were the typical distribution characteristics of the microelements for the acid soil in south China. The contents of available microelements were lack or unbalanced in a few orchard soils and inadequate in most of orchard soils. Therefore, it is necessary to add microelement fertilizer appropriately, especially for boron fertilizer.2. The main soil types in Gannan navel orange orchards were red soil, yellow soil, paddy soil and purple soil. The nutrient elements and available microelements in orchard soils varied with the soil types. The available contents of microelements in paddy soils were higher than other soil types, and the available contents of microelements in yellow soils were lowest. Therefore, the content of available microelements should be kept the balance by fertilization for the navel orange orchards of yellow soil.3. The soil available contents of Cu and Zn increased obviously with the increase of plantation age within about 10 years, and then flattened out after that. The soil available B contents increased with the increase of plantation age within 15 years. No obvious variations of the available contents of Fe and Mn with the plantation age were observed. Therefore, the microelements should be added timely in soils of newly planted orchards for increasing thecontents of available microelements.4. Positive correlations between soil p H and the available contents of Cu, Fe, Mn and Zn indicated it was helpful for improving the contents of available microelements to reduce appropriately the soil acidity through the way of applying lime in orchard soils. In addition, the organic matter contents in soils were correlated positively with the available contents of Cu, Fe,and Zn in the study region, suggesting the importance of improving soil organic matter.