Relationships between growth, mineral nutrition and site factors for Eucalyptus camaldulensis (Dehnh) planted in some communal areas of Zimbabwe

Abstract

The Forestry Commission of Zimbabwe has been implementing a Rural Afforestation Project since 1983. The main species promoted were the eucalypts, especially Eucalyptus camaldulensis (Dehnh). A survey of twenty-seven woodlots of E. camaldulensis with ages between I and 10 years was conducted across agro-ecological regions I to V whose annual precipitation range from I 000 mm to below 650 mm of erratic rainfall respectively. The objective was to establish the growth performance on-farm and relationships with soil and foliar nutrients. Growth was very variable, ranging from below I at Chiredzi, Zaka, Mwenezi and Bikita (all in agro-ecological regions IV and V) to almost 14 m³/ha/a at Makoni, which is in agro-ecological region I. Ten of the eleven woodlots in agro-ecological region IV and V had mean annual increments below 2,0 m³/ha/a. No relationships were established between growth parameters and soil pH, phosphorus, nitrogen and potassium. Growth was highly correlated to the mean annual rainfall of a site. There was marked variation in magnitudes of foliar nutrients across sites; ranging from 2 times for zinc, nitrogen and phosphorus to almost 30 times for manganese. Growth was also correlated to foliar boron, copper and manganese.

Keywords:

• Eucalyptus camaldulensis
• on-farm planting
• diameter at breast height
• height
• mean annual increment
• foliar nutrients