Organic matter and shading on ion accumulation in soil cultivated with noni under salinity

ABSTRACT This study aimed to evaluate the influence of organic matter on the salt accumulation in three layers of soil cultivated with noni plants irrigated with brackish water, in open field and under partial shading conditions. The experimental design was in randomized blocks, arranged in a split-split-plot scheme with five replicates. The plots were constituted by the cultivation environments (open and shaded field), the subplots by the electrical conductivity of the irrigation water (0.3, 1.5, 3.0, 4.5, and 6.0 dS m-1), and the sub-subplots by the absence and presence of organic matter. At 110 days after application of the treatments, the electrical conductivity of the saturation extract and the potassium, sodium, calcium, and magnesium concentrations were determined in three soil layers (0-10, 10-20, and 20-30 cm). Partial shading reduced the total accumulation of salts and sodium in the soil compared to the open field. Increasing the electrical conductivity of irrigation water reduced potassium concentrations in the soil, but this effect is offset by the addition of organic matter, which releases potassium, calcium, and magnesium for plant nutrition. However, cattle manure increases sodium accumulation in the soil in treatments with the highest water salinity.摘要 本研究旨在评估露地与部分遮荫两种栽培环境下，采用咸水灌溉的诺丽（Noni）种植土壤三层中的盐分累积受有机质的影响。本试验采用随机区组设计，以裂裂区（split-split-plot）布局设置，共设5次重复。主区为栽培环境（露地与遮荫田），副区为灌溉水电导率（0.3、1.5、3.0、4.5、6.0 dS·m⁻¹），副副区为有机质添加与否。于处理施加110天后，测定三层土壤（0~10 cm、10~20 cm、20~30 cm）的饱和浸提液电导率，以及钾、钠、钙、镁的含量。与露地栽培相比，部分遮荫可降低土壤中盐分与钠的总累积量。提高灌溉水电导率会降低土壤钾含量，但该效应可通过添加有机质得到抵消——有机质可为植株营养释放钾、钙、镁元素。但在灌溉水盐度最高的处理组中，施用牛粪会增加土壤钠的累积量。