Effects of application of lime nitrogen and dicyandiamide on nitrous oxide emissions from green tea fields

Abstract

The aim of this study was to assess the mitigating effects of lime nitrogen (calcium cyanamide) and dicyandiamide (DCD) application on nitrous oxide (N 2 O) emissions from fields of green tea [Camellia sinensis (L.) Kuntze]. The study was conducted in experimental tea fields in which the fertilizer application rate was 544 kg nitrogen (N) ha −1 yr −1 for 2 years. The mean cumulative N 2 O flux from the soil between the canopies of tea plants for 2 years was 7.1 ± 0.9 kg N ha −1 yr −1 in control plots. The cumulative N 2 O flux in the plots supplemented with lime nitrogen was 3.5 ± 0.1 kgN ha −1 , approximately 51% lower than that in control plots. This reduction was due to the inhibition of nitrification by DCD, which was produced from the lime nitrogen. In addition, the increase in soil pH by lime in the lime nitrogen may also be another reason for the decreased N 2 O emissions from soil in LN plots. Meanwhile, the cumulative N 2 O flux in DCD plots was not significantly different from that in control plots. The seasonal variability in N 2 O emissions in DCD plots differed from that in control plots and application of DCD sometimes increased N 2 O emissions from tea field soil. The nitrification inhibition effect of lime nitrogen and DCD helped to delay nitrification of ammonium-nitrogen (NH 4 + -N), leading to high NH 4 + -N concentrations and a high ratio of NH 4 + -N /nitrate-nitrogen (NO 3 --N) in the soil. The inhibitors delayed the formation of NO 3 --N in soil. N uptake by tea plants was almost the same among all three treatments.

Environmental and nutritional requirements for tea cultivation

“…, which means that they are much higher than those in other crop fields (Hirono and Nonaka 2014). Out of the inorganic NPK applied annually, only 25-50% are taken up by plants and the rest is lost through leaching, erosion, denitrification or volatilization (in the case of N), or is immobilized in soil organic matter (Roberts 2008).…”

Is green tea still ‘green’?

“…A number of field studies for the continuous measurement of N 2 O fluxes from tea plantations in Japan (Akiyama et al ; Hirono and Nonaka, ; Hirono and Nonaka, ; Yamamoto et al ; Hou et al ), China (Fu et al ; Fu, ; Han et al ; Yao et al ) and India (Gogoi and Baruah, ), and data from East Asia have shown large amounts of N 2 O emissions from tea plantations, being much greater than those in cereal cropped fields on a hectare basis. Under common management practices, tea plantations can emit up to 61.0 kg N 2 O‐N ha –1 year –1 (Table ).…”

“…In Japan, lime‐N applications in tea plantations were shown to evidently reduce N 2 O emissions by 36–51% by inhibiting both nitrification and denitrification processes in acidic soils (Hirono and Nonaka, ; Yamamoto et al ), while in China, we carried out a two‐year investigation of continuously measuring N 2 O emissions from a conventional practice and six mitigation options in a commercial tea field in Hunan Province (Figure ). We found that mitigating N 2 O emissions from tea plantations is challenging, because only the treatments of white clover intercropping, deep fertiliser placement below 20 cm and controlled‐release fertiliser (CRF) at a half rate showed a limited reduction of N 2 O emissions, by 9.5%, 19.3% and 21.3%, respectively, compared with the conventional treatment.…”

Fate of Fertilizer-Derived N Applied to Enhance Rice Straw Decomposition in a Paddy Field during the Fallow Season under Cool Temperature Conditions

“…The Ministry of Agriculture, Forestry and Fisheries of Japan authorized LN as a type of controlled-release fertilizer in 2013. Recently, the reduction of nitrous oxide emissions from the uplands and tea fields via the application of LN have frequently been verified, highlighting the nitrification inhibitory effect of this compound [6][7][8][9].…”