桂东南荔枝生长营养元素农业地球化学研究

桂东南是中国重要的荔枝产区,以梧州地区为例,重点对沙头和古凤两处荔枝种植园进行了生态地球化学调查,采集了荔枝园施肥圈内、外土壤,出露的代表性基岩,以及荔枝叶、青果和熟果样品,实测了大量和微量矿质元素、稀土元素,以及土壤营养元素有效态的含量。通过计算荔枝对土壤营养元素的吸收率及荔枝生长与结果期对营养元素的需求,查明本区荔枝生长的特征营养元素为Ca、K、Mg、Mn、P、Zn、Cu、B、Fe和REE。荔枝结果期的特需营养元素为P、Mg、Mo、Cu、Zn、Ko荔枝结果早和晚期特需元素分别为Ca、Si、B和Cu、Fe、K。在岩石-土壤-荔枝株生态循环系统中,本区营养元素在土壤中保持一定的积累,提供荔枝生长的需求,因此为荔枝宜种区;但全区土壤B缺乏,Zn、Mo局部不足。Ca、K、Zn在两区岩石土壤中分布不同,可能是造成沙头荔枝比古凤荔枝迟熟的主要农业地球化学因素。研究区有害元素Pb、Cd在土壤中积累是值得关注的土壤环境问题。

Agro-geochemistry study of the nutrient elements in a litchi plantation soil in southeast Guangxi Province, South China

The authors have carried out an investigation of Gufeng and Shatou litchi plantation field in Wuzhou area, Guangxi Province, South China. A calculation of absorption coefficient and requirements of soil elements for the growing of litchi shows that Ca, K, Mg, Mn, P, Zn, Cu, B, Fe and REE are the specific nutrient elements in this area, and that nutrient elements needed for litehi production are P, Mg, Mo, Cu, Zn, K. Ca, Si, B are needed at the early stages of litchi production time, and Cu, Fe, K at later stages of production and growth. Through analyzing the migration and mass balance of nutrient elements in the bedrock-soil-litchi mass as an ecologic system, we find that the bulk of nutrient elements enriched and accumulated in the soil provide sufficient supplies for the growth and production of litchi. Therefore, the soil of southeast Guangxi area is suitable for litehi plantations; but this study also demonstrates that the soil in study area is deficient in B and poor in Zn and Mo in some localities. The different distribution of Ca, Mg, K, Zn in bedrocks and soils between Gufeng and Shatou plantation areas may be the cause of late ripeness in Shatou type plantation, where the basement rock is shale. The authors also point out that in the soil of southeast Guangxi the toxic elements, such as Ph and Cd also accumulate and represent a potential hazard.