دانلود رایگان مقاله انگلیسی اثرات کاربرد نیتروژن بر روی اسیدی شدن و حل محلول شیمیایی گیاه چای - الزویر 2018

ABSTRACT

In tea (Camellia sinensis) plantation areas, soil acidification mainly results from excessive nitrogen fertilization. However, the proposed theoretical explanations for soil acidification due to nitrogen fertilization are still lacking empirical validation because most studies have used short-term incubation periods or pot experiments. Here, both soil and soil solution samples were taken from a tea plantation field (Ultisol in USDA taxonomy system, or Alisol in WRB taxonomy system) treated using different nitrogen application rates: 0 (N0), 119 (N119), 285 (N285), and 569 (N569) kg N ha−1 yr−1 for 8 years (2006–2013). Soil pH and the concentrations of the relevant cations and anions were also determined. With no nitrogen fertilization (N0), the surface soil pH decreased from 4.16 to 3.32 after 8 years in the tea plantation. Compared with no nitrogen fertilization (N0), high nitrogen fertilization (N569) significantly decreased the soil pH from 3.32 to 3.15 and 3.67 to 3.35 in the soil at depths of 0–40 cm and 40–90 cm, respectively. However, the low (N119) and moderate (N285) nitrogen treatments showed non-significant effects upon soil pH. Our results confirm the previous findings that a high nitrogen application rate can accelerate soil acidification in a tea plantation, and that the subsoil is particularly susceptible to acidification after heavy nitrogen fertilization. Soil acidification also significantly decreased the nutrient base cations Ca2+, Mg2+, and K+ in the soil. Our results suggest that heavy synthetic nitrogen fertilization should be partly replaced with compound or organic fertilizers to mitigate soil acidification and nutrient cation deficiency in tea plantation fields.

5. Conclusions

The presented study confirmed that naturally occurring soil acidification occurs in a tea plantation at an estimated annual rate of 0.071. A high N application accelerated the soil acidification process, and reduced the ANC and BS, whereas apparently neither low N nor moderate N applications influenced the soil acidity. The applied N rate also significantly altered the cation and anion composition in both the topsoil and subsoil. Base cations were remarkably decreased under the high N treatment in the topsoil, but no so in the subsoil. Conversely, the high N input favored the accumulation of exchangeable Al3+, rather than exchangeable H+, in both the topsoil and subsoil. Based on these results, an appropriate synthetic N application rate or alkaline materials should be recommended in tea plantations to mitigate the risk of soil acidification and deficiencies in the vital nutrients K+, Ca2+, and Mg2+.