Abstract
Lack of science-based knowledge on responses of tea bushes to nitrogen (N) in ageing tea plantations hampers the development of ecologically sound and economically profitable N-management strategies. It is hypothesized that ageing of tea plantations lowers productivity and weakens the yield response to N application. To establish insight into the relationship between ageing, productivity and N-use efficiency, seasonal and annual responses to N were studied in field experiments superimposed on a chronosequence of tea plantations (14, 29, 43, and 76 years). The two youngest plantations comprised of a clonal cultivar planted at a density of 10,766 and 13,448 plants ha(-1) and the two oldest plantations of seedlings at a density of 6730 and 7179 plants ha(-1), respectively. N was applied as urea at 0, 50,100,200, and 400 kg N ha(-1) year(-1). Mean annual made tea (mt) yields were higher for the clonal tea compared to the seedling tea and increased with age within genotypes. The clonal bushes out-yielded the seedlings by about 800 kg mt ha(-1) under favourable weather conditions in 2003/2004, while yield differences between the genotypes were minimal under stress conditions in 2002/2003. The yields of the clonal 29- and 14-year-old plantations responded positively to N fertilizer, whereas the 43- and 76-year-old plantations did not. Within the clonal cultivar made tea yield and N uptake were closely associated. Apparent shoot N-recovery (ASNR) based on N uptake by 'two leaves and a bud' was higher in clonal than in seedling tea plantations. A simple N-balance sheet showed that N excess was strongly associated with the rate of N application and N uptake. The effect of plant genotype on productivity was greater than the effect of age. The genotypes (seedlings or a clonal cultivar) to a great extent determined the yield response to N. In a well-managed mature tea plantation of up to 80 years, ageing did not lower the yielding ability within the same genotype. Thus, planting improved genotypes and implementing appropriate N-management strategies are key factors to avoid the risk on decline of productivity and profitability associated with ageing and bush degradation. N-management strategies should be based on the yielding potential of tea bushes in the target environment as defined by plant genotype and age of plantations. (C) 2008 Elsevier B.V. All rights reserved.
Original language | English |
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Pages (from-to) | 60-70 |
Journal | Field Crops Research |
Volume | 108 |
Issue number | 1 |
DOIs | |
Publication status | Published - 2008 |
Keywords
- dry-matter production
- seasonal yield variation
- camellia-sinensis l.
- black tea
- potential production
- research-foundation
- cuppa-tea
- water-use
- responses
- kenya