The Status of Zn, Cu, Mil, and Fe in the Soils and Tea Leaves of Kibena Tea Estates, Njombe, Tanzania

Abstract

A study was undertaken to assess Zn, Cu, Mn, and Fe status of the soils and tea plants at Kibena Teat Estates in Njombe, Tanzania. Low yields of tea in these estates prompted this study to identify some of the constraints to tea production. Twenty four composite soil samples were randomly collected to a depth of 0-40cm from the six divisions of the Kibena Tea Estates, namely; North, Lihogosa, Kilolelo, Central Matombololo and Itambo. The third leaf of the tea plants were harvested from plants close to where the soils were sampled. The soils and leaves were analyzed for available and contents of Zn, Cu, Mn and Fe, respectively. DTPA extractable Zn and Cu were consistently low in almost all the soil samples, which ranged from 0.08 to 0.93 mg Znkg^-1 and 0.04 to 0.34 mg Cukg^-1 soil. On the other hands, Fe and Mn were sufficientfor the tea plants and ranged from 26. 88 to 60.28 mg Fekg^-1 and 7.65 to 31.18 mg Mnkg^-1 soil. The plant leaf Mn, and Zn were above the critical levels in most of the plant samples, a reflection of their high contents in the soils and foliar application at a rate of 2 kgha^-1, respectively. Although Fe was observed to be sufficient in soils, it was poorly reflected in tea leaves of which 65.22% of samples were deficient. This phenomena is explained by high levels of Zn in tea leaves which reduces the uptake of Fe from soils. The low content of Cu in leaves are consequences of low level of extractable Cu in soils and high levels of Fe in soils which induces Cu deficiency. The availability of Cu, Zn, Mn and Fe were largely controlled by the pH of the soils which ranged from 4.01 to 5.51. Application ofCu and Zn fertilizers were recommended as soil fertility management strategies for sustainable tea production at the Kibena Tea Estates.

Keywords: zinc, copper, manganese; iron, critical levels, third leaf, DTPA extractable

Tanzania J.Agri.Sc.(2006)-Vol.7 No.1, 34-41