Corymbia citriodora, also known as lemon eucalyptus, is one of the most cultivated species for extraction of essential oils. Seedling production for this species, however, is more difficult than for other species, considering its slower growth, higher susceptibility to disease and nutrition requirements. As regards top dressing in particular, no established routine is available so far to ensure fertilizer savings and good seedling development. Slow growth reduces seedling capability to absorb nutrients before leaching starts, and a potential alternative to that is to add water-retaining polymers to the substrate so as to facilitate absorption of the fertilizers applied and their slow release in seedling tubes. The objective of this study was to evaluate the effect of different fertilizer dosages, as applied to substrates containing water-retaining polymers, on the growth of Corymbia citriodora seedlings. A completely randomized design was used, with four replicates, consisting of a control treatment with routine substrate and fertilizer used by a commercial nursery, plus five treatments with top dressing dosages ranging from 80% to 20% of commercial dosage plus addition of a polymer (6 g L-1). After 126 days, seedlings were evaluated for height, stem base diameter and ratio of height to stem base diameter. After analysis, it was concluded that the use of a water-retaining polymer had a positive effect on the height, stem base diameter and ratio of shoot height to stem base diameter, and that it helped reduce by at least 20% the amount of routine fertilizer used by the commercial nursery, whether basic fertilizer or top dressing.
Water-retaining polymers; seedling production; fertilizer savings
