Net and gross nitrification in tea soils of varying productivity and their adjacent forest and vegetable soils

Abstract

Tea (Camellia sinensis (L.) O. Kuntze) is a globally important crop and is unusual because it both requires and acidifies the soil in which it grows. In spite of the low pH, high nitrate (NO À 3 ) accumulates in tea soils, resulting in a great potential for diffuse pollution. Nitrification in tea soils remains poorly understood. The purpose of this study was to investigate net and gross nitrification in three tea soils with varying productivity, their adjacent forest and vegetable soils. The results showed that neither net nor gross nitrification rates were significantly related to soil pH. The net nitrification rate increased with increasing tea production, and when soils were incubated with ammonium sulfate. The ammonium (NH þ 4 ) added to the vegetable soil was immediately and completely nitrified, but that in the tea and forest soils was nitrified more slowly. About 60-80% of the NH þ 4 in the tea and forest soils was nitrified during 35 d of incubation, indicating nitrifiers do exist in these soils. Significantly higher gross nitrification rates were observed in vegetable and tea soils with high and medium production than in forest and tea soils with low production. Microbial consumption (immobilization and nitrate respiration) accounted for 30 to 70% of the mineralized nitrate nitrogen (NO À 3 ÀN) with the lowest in the forest soil, and no significant difference between the tea and vegetable soils. Nitrogen fertilizer stimulated soil nitrification. In conclusion, the types of land use and their management are more important than soil pH for soil nitrification. High nitrogen application rate is the main cause of NO À 3 accumulation in tea soils and should be reduced to minimize NO À 3 pollution of water resources.

Soil carbon sequestration, plant nutrients and biological activities affected by organic farming system in tea (Camellia sinensis(L.) O. Kuntze) fields

“…However, the opposite results were also found in Yiwu and Jiangshan farms with conventional fields having significantly higher nitrification rates (Table 5). This is probably because the chemically N fertilized soils have a higher nitrification substrate, nitrifying activity and an accelerated growth of the nitrifying population (Chu et al 2008;Gong et al 2011;Han et al 2012). In this study, we found these two farms had higher initial NH 4 + -N compared to other sites, and the initial NH 4 + -N concentration was significantly correlated with the nitrification rate (r = 0.683, n = 11, p < 0.05).…”

Effect of orchard age on soil nitrogen transformation in subtropical China and implications

“…However, when forestlands are converted to agricultural lands, nitrification is stimulated and microbial immobilization of NO 3 − is substantially suppressed (Yang et al, 2008;Zhang et al, 2013a). Therefore, NO 3 − dominance in inorganic N in agricultural soils and the mechanism of N retention in humid subtropical soils is destroyed (Yang et al, 2010;Han et al, 2012;Zhang et al, 2013a). It has been observed that management practices, such as fertilization, stimulate the activity of nitrifying bacteria (e.g.…”

Aluminum and nutrient interplay across an age-chronosequence of tea plantations within a hilly red soil farm of subtropical China

“…Previous studies have well reported the cycle of individual elements, such as Al (Flaten 2002), N (Han et al 2012) and P (Debnath et al 2011) in tea plantations, which were generally tested by our study. However, we know little about at what points the major biogeochemical cycles interact and how these linkages are affected by environmental change and fertilization management and the development of tea plantations (Marklein and Houlton 2012).…”

“…Currently, there are 3 million ha of tea plantations, globally (Xue et al 2013). In subtropical China, most of the tea-growing areas are acidic-leached red soil (Ultisols) with poor amounts of available nutrients (Han et al 2007;Debnath et al 2011;Han et al 2012). And soil Al availability, in forms such as soluble Al, exchangeable Al and organic Al complexes, has increased with an increased acidic environment in this area.…”