攀枝花地区芒果园土壤pH现状及变化趋势

Current status and change tendency of soil pH in mango orchards in Panzhihua City, China

土壤pH是影响植物生长的关键因子,通常受到不合理的农业活动的影响而发生变化.为了解攀枝花芒果种植区土壤pH现状及其芒果种植适宜性,阐明果园土壤pH变化趋势及施肥管理对土壤pH的影响,选择不同海拔梯度(河谷区:950-1200 m;低山区:1200-1500 m;中山区:1500-1800 m)和发育阶段(挂果初期:2-5年;挂果前期:6-10年;挂果盛期:10-26年)芒果园共162个,测定树盘和间空区不同深度(0-20、20-40 cm)土壤pH值.结果显示,种植区土壤pH在4.0-8.4之间,约63.5%果园土壤pH处于芒果生长适宜范围内(5.5-7.5);中山区土壤pH显著低于河谷和低山区;种植区内土壤发生酸化的果园比例高于碱化果园;酸化果园占比大小为挂果初期>前期>盛期;碱化果园中,挂果盛期土壤碱化程度显著高于其他发育阶段;仅施用复合肥施用而未施用石灰及土壤调理剂的果园土壤酸化程度高于施用石灰或调理剂的果园,施用石灰或调理剂可以在短期内缓解表层土壤的酸化趋势,但对深层土壤的酸化无明显效果.上述结果表明,种植区有较大比例的果园土壤pH适宜性较差;现有施肥体系导致土壤酸碱化趋势分化明显,酸化与长期施用复合肥有关,碱化则与施用石灰与调理剂有关;研究结果对提高芒果种植施肥管理水平及改善土壤质量具有指导意义.

Soil pH, which seriously affects the growth and development of plants, is influenced by irrational agricultural activities. This study aimed to reveal the current status of soil pH and suitability in mango planting areas in Panzhihua city. Soil pH changes and the effect of fertilization management were also investigated. We analyzed soil pH in the beneath canopy area(BCA) and the inter space area(ISA) from 162 mango orchards at different altitude gradients(Valley area: 950-1 200 m;Lower mountain area: 1 200-1 500 m;Middle mountain area: 1 500-1 800 m) and different cultivated stages(Before fruiting stage: 2-5 a;Early fruiting stage: 6-10 a;Prosperous fruiting stage: 11-26 a) in Panzhihua city. The results indicated that soil pH varied from 4.0-8.4. In 63.5% of orchards, soil pH ranged from 5.5 to 7.5 which was optimum for mango growth. pH in the middle mountain area was significantly lower than that in the valley and lower mountain areas. At 0-20 cm soil depth, soil pH in 56.94% of the sites decreased and increased in 43.06% of the sites. At 20-40 cm soil depth, soil pH decreased in 70.42% and increased in 29.58%. The percentage of soil acidification(decreasing soil pH) in orchards among cultivated stages was ranked as Early fruiting stage > Before fruiting stage > Prosperous fruiting stage. Among soil alkalization orchards(increasing soil pH), the increase in pH in the Prosperous fruiting stage was higher than that in the other two stages. We also found that the decrease in pH was higher in orchards that only used N(Nitrogen), P(Phosphorus), and K(potassium) fertilizers than in the those using NPK fertilizers combined with lime and soil conditioner. In the short term, using lime and soil conditioner in the surface layer could alleviate the acidification tendency in topsoil, but has no obvious effect on deep soil. However, there remains a need to address the unsuitable pH levels in the remaining 36.5% of mango orchards. Further, existing mango fertilization management has led to different change tendencies in soil pH. Soil acidification is related to long term use of chemical NPK fertilizers, and soil alkalization is related to lime and soil conditioner use. These results could provide theoretical guidance for improving the level of mango fertilization management and the soil quality in Panzhihua mango planting area.