关键词: 红壤, 土壤酸化, 土地利用方式, 氮循环过程, 湖南祁阳县

Abstract:

【Objective】In Qiyang County, Hunan Province which is a typical county of China, quantifying key acidity inducing factors could provide theoretical bases for combating soil acidification, and provide scientific and technological supports for red soil acidification remediation in China. 【Method】To achieve our objective, data of fertilizer rate, biomass (or yield) of main crops and trees, and above-ground nutrient contents reported within the experimental site were obtained from a large number of published literatures and statistical yearbooks. We quantified the acidity-inducing factors (nitrogen cycling process, BC (base cation) absorption and acid deposition) based on classical mass and charge balance. Relative contributions of the three key processes were used to illustrate the dominant factor of the soil acidification in uplands, paddy fields and woodlands. 【Result】For the whole county, nitrogen cycling process accounted for 66.5% (65.3% - 68.8%) of the total H ⁺ production, base absorption accounted for 33.0% (30.1%-34.4%), and acid deposition accounted for 0.5% (0.3% - 1.7%). Regardless of the land use patterns, nitrogen cycling process was the main source of H ⁺ production and main controlling factor of soil acidification. Among the three land use patterns, H ⁺ net production of upland was the highest (19.01 kmol·hm ^-2·a ^-1), followed by paddy field (16.5 kmol·hm ^-2·a ^-1), and woodland (3.2 kmol·hm ^-2·a ^-1) as the lowest. H ⁺ net production in dry farmland was about 6 times of woodland. H ⁺ net production of 6 main crop systems varies from 10.1 kmol·hm ^-2·a ^-1 to 30.0 kmol·hm ^-2·a ^-1, and followed the order: soybean>rape>peanut>rice>corn>sweet potato. Acidity production of the economic crops (rape, peanut and soybean) was generally higher than that of the grains (rice, corn, sweet potato); contribution rate of acidity-inducing of nitrogen cycling process among 6 main crop systems varied from 45.3% to 78.3%, contribution rate of acidity-inducing of base absorption varied from 21.4% to 54.2% . H ⁺ net production of 7 main woodland systems varied greatly from 1.96 kmol·hm ^-2·a ^-1 to 27.8 kmol·hm ^-2·a ^-1, and followed the order: citrus>chestnut>camellia oleifera abel>pine>fir>bamboo>slash pine. Acidity production of economic forest (citrus, chestnut and camellia oleifera abel) was generally higher than that of timber forest (pine, fir, bamboo and slash pine) ; contribution rate of acidity-inducing of nitrogen cycling process among 7 main woodland systems varied from 46.1% to 80.8%, and contribution rate of acidity-inducing of base absorption varied from 19.0% to 53.3% . The long-term field experiment combined with soil buffering curve technique was used to verify reliability of the calculation method of H ⁺ production. The simulated value of soil pH was positively correlated with the measured value significantly, with root mean square error (RMSE) of 0.15, while anastomosis degree between the two was high. 【Conclusion】 Nitrogen cycling process was the main controlling factor of red soil acidification in Qiyang County. The differences of total acidity production and contribution of acidity-inducing factors depended largely on land use patterns, crop types and tree species.

Key words: red soil, soil acidification, land use patterns, nitrogen cycling process, Qiyang County,Hunan Province