A comparison of different planting methods, including hydrogels, and their effect on eucalypt survival and initial growth in South Africa

Abstract

Research to minimize mortality and enhance early growth during the re-establishment of eucalypts includes the use of optimum growing stock and planting techniques, the application of adequate volumes of water at planting (where appropriate), correct fertilizer application and placement, and optimum environmental conditions at planting. The use of hydrogels at planting, Stockosorb^® 400K in particular, has also shown improvements in seedling survival and initial growth when planted under adverse conditions. The reformulation of this hydrogel through the addition of plant nutrients (Aquasoil^TM) was marketed to enhance initial growth whilst retaining the inherent benefits of the hydrogel component. Whether Aquasoil^TM could replace the use of a granular fertilizer thus needed to be tested. Three field trials were implemented covering a range of soils, climates and eucalypt species to compare the effect of Aquasoil^TM together with various planting practices, including those of planting with, or without water, or Stockosorb^® 400K (water and Stockosorb^® 400K treatments were also tested with or without the application of a granular fertilizer) on eucalypt survival and initial growth. Results from these trials indicated that: i) planting without water generally resulted in poorer survival and growth, ii) although planting with water improved survival, growth was inconsistent and not always the best, iii) the application of a hydrogel (Stockosorb^® 400K) consistently increased seedling survival and initial growth during sub-optimal planting conditions, iv) the surface application of granular fertilizer (whether used in combination with water or a hydrogel) at planting produced the fastest and largest growth responses of all treatments, and v) the use of Aquasoil^TM (hydrogel combined with nutrients) to significantly improve survival and initial growth produced inconsistent results when compared to the application of a hydrogel only (no additional nutrients added).

Southern African Forestry Journal Vol. 208, 2006: 5-13