Productivity and nitrogen use of tea plantations in relation to age and genotype

• Published in: Field crops research 2008-07, Vol.108 (1), p.60-70
• Main Authors: Kamau, D.M., Spiertz, J.H.J., Oenema, O., Owuor, P.O.
• Format: Article
• Language: English
• Subjects: Age; Ageing of tea bushes; Agrochemicals; black tea; Camellia sinensis; Camellia sinensis (L.); chronosequences; Clone; clones; crop yield; Crops; cultivars; cuppa-tea; dry-matter production; Economics; fertilizer rates; Fertilizers; field experimentation; genotype; Genotypes; kenya; Made tea yield; meteorological parameters; N uptake; Nitrogen; nitrogen fertilizers; nutrient management; nutrient uptake; nutrient use efficiency; plant age; plant density; plant nutrition; plant stress; plantations; planting; potential production; profitability; Q1; research-foundation; responses; seasonal variation; Seasonal variations; seasonal yield variation; Seedlings; shoots; Stress; Sulfur dioxide; tea; urea; water-use; Weather
• ISSN: 0378-4290; 1872-6852
• DOI: 10.1016/j.fcr.2008.03.003

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.