Abstract:

Soil pH and organic matter content are important indicators for evaluating soil physicochemical properties and fertilizer retention capacity. To date, it remains poorly understood the temporal and spatial changes in pH and organic matter in the soils of Guangdong Province since 2016. In this study, changes in soil pH, organic matter content, and their influencing factors since 2016 were analyzed using fixed-point monitoring data from the entire Guangdong province. The results showed that the average value of soil pH was 5.41 for the whole province in 2016‒2018, with the average value of different land use types being ranked as follows: dry land>paddy field>garden land≈forest land. The average value of soil pH increased to 5.46 for the whole province during 2021‒2022, with the order of average values of different land use types being unchanged. Compared with the 2016‒2018 period, the average soil pH value of paddy field increased by 0.12 units while that of forest land decreased by 0.14 units during the 2021‒2022 period, with the most obvious fluctuations being observed in the mountainous areas of Northern Guangdong and some areas of the Pearl River Delta region. However, the average soil pH values did not change significantly in the dry or garden lands. The average soil organic matter was 24.07 g∙kg⁻¹ for the whole province in 2016‒2018, with the average value of different land use types ranked as follows: paddy field≈forest land>garden land≈dry land. The average value of soil organic matter decreased to 23.23 g∙kg⁻¹ for the entire province during 2021‒2022, with the order of average values of different land use types changing to paddy fields>forest land>dry land. There were no significant differences between garden and forest lands, or between garden and dry lands. Compared with the 2016‒2018 period, the average values of paddy field and forest land decreased by 0.93 g∙kg⁻¹ and 3.84 g∙kg⁻¹, respectively during the 2021‒2022 period, with the decreases being observed mainly in the mountainous areas of Northern Guangdong. However, the average values of soil organic matter did not change significantly in the dry and garden lands. Meteorological conditions, land use type, and fertilizer application are important factors that affect soil pH and organic matter content. Suitable and stable temperature and moisture conditions are conducive to slowing down soil acidification and promoting organic matter accumulation. The maintenance of paddy fields was conducive to improving the soil pH and maintaining a relatively high organic matter content. Compared to paddy fields and dry land, forest soils are more prone to acidification and are unfavorable for the accumulation of organic matter. The effect of chemical fertilizer application on soil pH was higher in dry land than in paddy fields, and the effects of phosphate and potassium fertilizers may be greater than those of nitrogen fertilizers.

Key words: Guangdong, soil, pH, organic matter, temporal and spatial changes, influencing factors

摘要：

土壤pH和有机质含量是评价土壤理化性质和保肥能力的重要指标。利用覆盖广东全省的定点监测数据，对2016年以来土壤pH和有机质含量变化及其影响因素进行分析。结果表明，2016－2018年时期全省土壤pH均值为5.41，不同土地利用类型均值排序为旱地>水田>园地≈林地；2021－2022年时期全省均值升高至5.46，不同土地利用类型均值排序不变，但水田均值升高0.12单位，林地均值下降0.14单位，均以粤北山区和珠三角局部地区波动最明显，旱地和园地均值变化不显著。2016－2018年时期全省土壤有机质含量均值为24.07 g∙kg⁻¹，不同土地利用类型均值排序为水田≈林地>园地≈旱地；2021－2022年时期全省均值降低至23.23 g∙kg⁻¹，不同土地利用类型均值排序变为水田>林地>旱地，园地与林地间或园地与旱地间差异不显著，其中水田和林地均值分别下降0.93 g∙kg⁻¹和3.84 g∙kg⁻¹，下降地区均集中在粤北山区，旱地和园地均值变化不显著。气象条件、土地利用类型和化肥施用是影响土壤pH和有机质含量的重要因素。适宜且稳定的温度和水分状况有利于减缓土壤酸化，促进有机质的积累。水田的保持有利于提高土壤pH、保有相对较高的有机质含量水平；与水田和旱地相比，林地土壤更易酸化且不利于有机质累积。化肥施用对旱地土壤pH的影响要高于水田，磷肥和钾肥的影响可能大于氮肥。

关键词: 广东, 土壤, pH, 有机质, 时空变化, 影响因素