CONTEXT

Village tank cascade system (VTCS) is a globally important agricultural heritage system in Dry Zone watersheds of Sri Lanka. Lands in these watersheds have been under changing management conditions in the recent past, hence their sustainability has been suspected.

OBJECTIVE

Objectives of this study were to determine current status of soil properties in different land uses and tank components of a VTCS with respect to their position in the watershed, and to assess sustainability of this agricultural system using soil organic carbon management index (CMI) as a proxy.

METHODS

Study was conducted in Mahakanumulla VTCS in North Central Dry Zone of Sri Lanka. Soil samples (n = 120) were collected from lands under forest, scrub/shrub, paddy and upland crops representing all elevations in two linear transects located in higher and lower positions along the main valley. Soils from components of tanks in upper and lower positions were also collected. Soil texture and some chemical properties were measured. The CMI in different land uses was calculated using total organic carbon (TOC) and permanganate oxidizable carbon contents.

RESULTS AND CONCLUSIONS

Effect of land use type on soil properties did not vary with position in the watershed (p > 0.05). An increase in available phosphorus and sulphur was observed in agricultural lands. Significant decreases in TOC (33%) and total N (43%) contents were observed in paddy lands compared to those of forest lands (p < 0.01). However, CMI indicated that management practices in paddy lands and upland soils are still sustainable but scrub/shrub lands need improvements to arrest their degradation. Electrical conductivity, pH, available P, K and Zn were significantly higher in lower positions while total N was lower. Thaulla (inundation area) and Perahana (filter) tank components had regulated flow of clay particles while Kattakaduwa (interceptor) has significantly high available P and TOC contents due to high wetness. Principal component analysis revealed factors that control soil erosion, soil organic matter content, water movement, cation availability and P dynamics governed the variability of major soil properties. Accumulation of soluble salts in lands of lower positions and increase of available plant nutrients in agricultural lands suggest that management practices so far adopted have slightly degraded soil fertility in this VTCS.

SIGNIFICANCE

Further degradation of soils in lower positions and scrub/shrub lands in the watershed will negatively affect the livelihood of villagers and the environment. Hence, appropriate land management policies should be introduced to this agricultural system to ensure their sustainability.

中文翻译：

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土地利用类型和储罐组分对斯里兰卡中北部干旱区土壤性质和储罐梯级系统可持续性的影响

语境

村庄罐级联系统（VTCS）是斯里兰卡干旱区流域的全球重要农业遗产系统。这些流域内的土地最近一直处于不断变化的管理条件下，因此人们怀疑它们的可持续性。

客观的

本研究的目的是确定不同土地利用和 VTCS 水箱组件在流域中的位置的土壤特性现状，并使用土壤有机碳管理指数 (CMI) 作为评估该农业系统的可持续性。代理人。

方法

研究在斯里兰卡中北部干旱区的Mahakanumulla VTCS 进行。土壤样品 ( n  = 120) 采集自森林、灌丛/灌木、稻田和高地作物，代表位于主要山谷较高和较低位置的两个线性样带中的所有海拔。还收集了来自上部和下部水箱组件的土壤。测量了土壤质地和一些化学性质。使用总有机碳 (TOC) 和高锰酸盐可氧化碳含量计算不同土地利用的 CMI。

结果和结论

土地利用类型对土壤性质的影响不随流域内的位置而变化（p  > 0.05）。在农田中观察到有效磷和硫的增加。与林地相比，水田的总有机碳（33%）和总氮（43%）含量显着降低（p  < 0.01）。然而，CMI 表示，稻田和高地土壤的管理实践仍然是可持续的，但灌丛/灌木地需要改进以阻止其退化。电导率、pH、有效磷、钾和锌在较低位置显着较高，而总氮较低。Thaulla（淹没区）和Perahana（过滤器）水箱组件调节了粘土颗粒的流动，而由于高湿度，Kattakaduwa （拦截器）具有显着高的有效 P 和 TOC 含量。主成分分析揭示了控制土壤侵蚀、土壤有机质含量、水分运动、阳离子有效性和磷动态的因素决定了主要土壤性质的变异性。可溶性盐在较低位置的土地上的积累和农业用地中可用植物养分的增加表明，迄今为止所采用的管理做法略微降低了该 VTCS 的土壤肥力。

意义

流域较低位置的土壤和灌丛/灌木地的进一步退化将对村民的生计和环境产生负面影响。因此，应在该农业系统中引入适当的土地管理政策，以确保其可持续性。