Nitrous oxide emissions from tea plantations: A review.

Tea plantations are an important N2O source. Fertilizer-induced N2O emission factors of tea plantations are much higher than other upland agricultural ecosystems. According to the basic information on characteristics and knowledge of N2O emissions from tea plantations around the world, we comprehensively reviewed N2O emission characteristics, production process, influencing factors, and reduction measures from tea plantations. The global means of ambient N2O emission and N2O emission stimulated by nitrogen fertilizer application from tea plantations were (2.68±2.92) kg N·hm-2 and (11.29±9.45) kg N·hm-2, respectively. The fertilizer-induced N2O emission factor in tea plantations (2.2%±2.1%) was much higher than the IPCC-estimated N2O emission factor for agricultural land (1%). N2O emission from tea plantation soil (a typical acid soil) were mainly produced during nitrification and denitrification, with denitrification being dominant. N2O emission from tea plantations were significantly related to the amount of fertilizer application. Other factors, such as fertilizer type, could also affect soil N2O emissions in tea plantations. The main reduction methods of N2O emission from tea plantations included optimizing the amount and type of fertilizer, amending biochar, and rationally using nitrification inhibitors. In future, we should strengthen in-situ observations of soil N2O emission from tea plantations at both temporal and spatial scales, combine lab incubation and field studies to elucidate the mechanisms underling tea plantation soil N2O emissions, and use a data-model fusion approach to reduce uncertainties in the estimation of global N2O emission. These would provide theoretical support and practical guidance for reasonable N2O emission reduction in tea plantations.

Long-term balanced fertilization increases the soil microbial functional diversity in a phosphorus-limited paddy soil.

The influence of long-term chemical fertilization on soil microbial communities has been one of the frontier topics of agricultural and environmental sciences and is critical for linking soil microbial flora with soil functions. In this study, 16S rRNA gene pyrosequencing and a functional gene array, geochip 4.0, were used to investigate the shifts in microbial composition and functional gene structure in paddy soils with different fertilization treatments over a 22-year period. These included a control without fertilizers; chemical nitrogen fertilizer (N); N and phosphate (NP); N and potassium (NK); and N, P and K (NPK). Based on 16S rRNA gene data, both species evenness and key genera were affected by P fertilization. Functional gene array-based analysis revealed that long-term fertilization significantly changed the overall microbial functional structures. Chemical fertilization significantly increased the diversity and abundance of most genes involved in C, N, P and S cycling, especially for the treatments NK and NPK. Significant correlations were found among functional gene structure and abundance, related soil enzymatic activities and rice yield, suggesting that a fertilizer-induced shift in the microbial community may accelerate the nutrient turnover in soil, which in turn influenced rice growth. The effect of N fertilization on soil microbial functional genes was mitigated by the addition of P fertilizer in this P-limited paddy soil, suggesting that balanced chemical fertilization is beneficial to the soil microbial community and its functions.

[Genetic diversity of microbial communities in tea orchard soil].

In this paper, the total microbial DNA was extracted from the soils in 8-, 50- and 90 years old tea orchards, adjacent wasteland, and 90 years old forestland in Meijiawu tea area of Hangzhou. The 16S rDNA V3 fragment was amplified by PCR, and the polymorphism of this fragment was analyzed by DGGE. The results indicated that both the tea orchard age and the land use type had significant effects on soil microbial genetic diversity. There was a significant difference (P < 0.05) in the microbial genetic diversity index among wasteland, tea orchards and forestland, which was decreased in the order of wasteland > tea orchard > forestland. For the tea orchards of different ages, the soil microbial genetic diversity index, microbial biomass C, and basal respiration were significantly higher in 50 years old than in 8 and 90 years old tea orchards.