Agroforestry systems are alternative solutions for production and management of agricultural systems which may improve soil quality. In this study, we evaluated the potential of coconut Cocos nucifera -based Gliricidia ( Gliricidia sepium ) systems to improve soil quality of coconut lands in Sri Lanka in dry and wet regions. A three-year field experiment was conducted in a randomized complete block design with three treatments T0, T5 and T20, being respectively the control, five and twenty years aged Gliricidia intercropped coconut-based mixed systems. Three replicates of soil samples were taken at 0–15, 15–30 and 30–45 cm and differences in soil physical and chemical properties were evaluated among treatments and sites. We found significant effects of mixed system treatments on the soil chemical properties. In particular, organic matter, soil exchangeable potassium, total nitrogen and available phosphorus contents showed higher values in most coconut-gliricidia mixed systems’ soils, with highest values obtained for T20. Cumulatively for all soil depths, organic matter content (22%) and available phosphorus content (20%) were higher on the wet site, and total exchangeable potassium content (69%) higher on the dry site for T20. The pH, bulk density, microbial respiration and electric conductivity did not vary among treatments, but were influenced by the site characteristics, with the dry site showing higher values for pH and the wet site showing higher values for bulk density (5%), microbial respiration (33%) and electric conductivity (2%) in T20 treatment. The study demonstrates that the systems with Gliricidia differed in their soil chemical attributes and had higher levels of soil nutrients when compared to coconut monocrop even at early ages, underlying the potential of Gliricidia for the rehabilitation of coconut growing soils.

中文翻译：

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Coconut-gliricidia 混合种植系统改善了斯里兰卡干湿地区的土壤养分

农林业系统是农业系统生产和管理的替代解决方案，可以改善土壤质量。在这项研究中，我们评估了基于椰子 Cocos nucifera 的 Gliricidia (Gliricidia sepium) 系统在改善斯里兰卡干湿地区椰子地土壤质量方面的潜力。在随机完整区组设计中进行了为期三年的田间试验，三个处理 T0、T5 和 T20，分别作为对照、5 年和 20 年的 Gliricidia 间作椰子混合系统。在 0-15、15-30 和 30-45 cm 处采集土壤样品的三个重复，并评估处理和地点之间土壤物理和化学性质的差异。我们发现混合系统处理对土壤化学性质的显着影响。特别是有机物，土壤可交换钾、全氮和有效磷含量在大多数椰子-蝾螈混合系统的土壤中显示出较高的值，T20 的值最高。对于所有土壤深度，T20 的累积有机质含量（22%）和有效磷含量（20%）在湿地较高，总交换钾含量（69%）在干地较高。pH、容重、微生物呼吸和电导率在不同处理间没有变化，但受场地特征的影响，干燥场地的 pH 值较高，湿场地的体积密度（5%）较高，微生物T20 处理中的呼吸 (33%) 和电导率 (2%)。