Urea–hydroxyapatite nanohybrid as an efficient nutrient source in Camellia sinensis (L.) Kuntze (tea)

Abstract

Slow-release fertilizers based on nanomaterials have recently proven promise in increasing nitrogen use efficiency by plants and reduction in environmental hazards. We have previously reported the synthesis of an efficient and novel plant nutrient formulation based on urea–hydroxyapatite (HA) nanohybrid and its efficacy at small scale field trials conducted using rice as the model crop. This work focuses on a study of the effect of urea–HA nanohybrid fertilizer on the yield and quality of tea in farmer’s fields selected from three climatic zones (Low Country, Mid Country, and UVA regions) in Sri Lanka for a period of three years. Experiments were carried out using treatments with half and full amounts of nitrogen recommendations to the tea plant, supplied through both conventional urea and nanohybrids at two and four splits per annum. Annual N requirement supplied through nanohybrids in Low Country and Uva showed a yield increment of 10–17% and 14–16%, respectively, compared with conventional recommendation. Nanohybrid fertilizer also allowed to reduce the number of fertilizer applications and the amount used by 50% resulting in matching yields to the conventional fertilizer applications. However, only a minute yield increase of 2–3% was observed in mid Country. Yield component analysis carried out in the Uva region was evident for increased tea yield obtained by application of slow-release nanofertilizer. Moreover, application of slow-release fertilizer significantly increased soil P, leaf N, and P concentration in Low Country tea yields. A positive effect of HA–urea nanohybrids was more pronounced during unfavorable climatic conditions.

Keywords:

• hydroxyapatite
• hydroxyapatite–urea nanohybrids
• mature tea
• nitrogen use efficiency
• slow-release
• soil and plant nutrient status
• yield

Acknowledgments

Authors wish to acknowledge the farmers who supported in field trial experiments. NK and VK acknowledge Sri Lanka Institute of Nanotechnology for providing facilities and funding to carry out this research during their seconded assessments from respective universities on national service.