Abstract. Effects of oil-palm (Elaeis guineensis Jacq.) management on silicon (Si) cycling under smallholder oil-palm plantations have hardly been investigated. As oil palms are Si accumulators, we hypothesized that management practices and topsoil erosion may cause Si losses and changes in spatial Si concentration patterns in topsoils under oil-palm cultivation. To test this hypothesis, we took topsoil samples under mature oil-palm plantations in well-drained and riparian areas of Jambi Province, Indonesia. The samples were taken from four different management zones within each oil-palm plot: palm circles, oil-palm rows, interrows and below frond piles. We quantified mobile Si (Si_M) and Si in amorphous silica (Si_Am) by CaCl₂ and NaCO₃ extraction, respectively. Both fractions are important Si pools in soils and are essential for plant-soil Si cycling. We further installed sediment traps on sloping, well-drained oil-palm plantations to estimate the annual loss of soil and Si_Am caused by erosion. In well-drained areas, mean topsoil Si_Am concentrations were significantly higher below frond piles (3.97 ±1.54 mg g^-1) compared to palm circles (1.71± 0.35 mg g^-1), oil-palm rows (1.87 ± 0.51 mg g^-1) and interrows (1.88 ± 0.39 mg g^-1). In riparian areas, highest mean topsoil Si_Am concentrations were also found below frond piles (2.96 ± 0.36 mg g^-1) and in grass-covered interrows (2.71 ± 0.13 mg g^-1), whereas topsoil Si_Am concentrations of palm circles were much lower (1.44 ± 0.55 mg g^-1). We attributed the high Si_Am concentrations in topsoils under frond piles and in grass-covered interrows to phytolith release from decaying oil-palm fronds, grasses, and sedges. The significantly lower Si_Am concentrations in palm circles (in both well-drained and riparian areas), oil-palm rows and unvegetated interrows (only in well-drained areas) were explained by a lack of litter return to these management zones. Mean topsoil Si_M concentrations were in a range of ~10 – 20 µg g^-1. They tended to be higher in riparian areas, but the differences between well-drained and riparian sites were not statistically significant. Soil-loss calculations based on erosion traps confirmed that topsoil erosion was considerable in oil-palm interrows on slopes. Erosion estimates were in a range of 4 – 6 Mg ha^-1 yr^-1, involving Si_Am losses in a range of 5 – 9 kg^-1 ha^-1 yr^-1. Based on the observed spatial Si patterns, we concluded that smallholders could efficiently reduce erosion and support Si cycling within the system by (1) maintaining a vegetation cover in oil-palm rows and interrows, (2) incorporating oil-palm litter into farm management and (3) preventing soil compaction and surface-crust formation.

中文翻译：

---

油棕管理改变了表土中无定形二氧化硅和流动硅的空间分布

摘要。几乎没有研究过油棕 ( Elaeis guineensis Jacq.) 管理对小农油棕种植园下硅 (Si) 循环的影响。由于油棕是 Si 积累者，我们假设管理实践和表土侵蚀可能导致 Si 损失和油棕种植下表土中 Si 空间浓度模式的变化。为了验证这一假设，我们在印度尼西亚占碑省排水良好和河岸地区的成熟油棕种植园下采集了表土样本。样本取自每个油棕地块内的四个不同管理区域：棕榈圈、油棕行、行间和叶堆下方。我们通过 CaCl ₂量化了无定形二氧化硅 (Si _Am ) 中的流动 Si (Si _{M ) 和 Si}和NaCO ₃萃取，分别。这两个部分都是土壤中重要的 Si 库，对于植物-土壤 Si 循环至关重要。我们进一步在倾斜、排水良好的油棕种植园安装了沉积物捕集器，以估计每年因侵蚀而造成的土壤和硅铝_流失。在排水良好的地区，与棕榈圈 (1.71± 0.35 mg g _-1 ) ^、油棕行 (1.87 ± 0.51 mg g ^-1 ) 和行间 (1.88 ± 0.39 mg g ^-1 )。在河岸地区，最高的平均表土 Si _Am浓度也在叶堆下方（2.96 ± 0.36 mg g ^-1) 和草覆盖的中间行 (2.71 ± 0.13 mg g ^-1 )，而棕榈圈的表土 Si _Am浓度要低得多 (1.44 ± 0.55 mg g ^-1 )。我们将叶堆下和草丛间的表土中的高 Si _{Am浓度归因于腐烂的油棕叶、草和莎草释放的植硅体。}棕榈圈（排水良好和河岸地区）、油棕行和无植被间行（仅在排水良好的地区）中Si _{Am浓度显着降低的原因是这些管理区没有垃圾返回。}平均表土 Si _M浓度范围为 ~10 – 20 µg g ^-1. 它们在河岸地区往往较高，但排水良好和河岸地点之间的差异没有统计学意义。基于侵蚀陷阱的土壤流失计算证实，在斜坡上的油棕间行中，表土侵蚀相当大。侵蚀估计在 4 – 6 Mg ha ^-1 yr ^-1范围内，其中 Si _Am损失在 5 – 9 kg ^-1 ha ^-1 yr ^-1范围内. 根据观察到的空间硅模式，我们得出结论，小农可以通过以下方式有效减少侵蚀并支持系统内的硅循环：（1）保持油棕行和行间植被覆盖，（2）将油棕垫料纳入农场管理(3) 防止土壤板结和地壳形成。