Includes bibliographical references and index.

Assessment of soil quality is required to determine the sustainability of land uses in terms of environmental quality and plant productivity. Long-term usage of a certain land use system may alter the physico-chemical characteristics of the soil, changing its fertility status and nutrient availability to plants. Zabo farming system is one of the important indigenous farming systems practiced by the Naga tribe in Nagaland. It is a three tier farming system which comprises integrated agricultural activities such forest land for silviculture (first tier), water harvesting, animal husbandry, vegetable growing area (second tier) and paddy-cum-fish farming (third tier). An investigation was carried out to study the physico-chemical properties and soil quality index of Zabo farming system. For this, 10 villages of Zabo farming system in Phek district of Nagaland were selected. From each of 10 villages, 3 sites (i.e. terrace, valley and hilltop forest as a reference) were selected and from each sites, one composite soil sample under 2 depths (0-15 cm and 15-30cm) were collected. The geo-position of each sampling site was recorded and altogether 60 composite samples (2 areas x 2 depths x 10 villages) + (1 forest area x 2 depths x 10 villages) were collected. The soil physico-chemical properties namely particle density, bulk density, soil texture, particulate organic matter, maximum water holding capacity, available nitrogen, phosphorus, potassium, sulphur, DTPA-Fe, Cu, Mn, Zn, RS Al, CEC, base saturation, exchangeable ion i.e. Ca + Mg, K+, Na+ were analyzed. For group comparison (10 villages and 10 forest site) non-parametric Kruskal-Wallis H-test incorporating Monte-Carlo significance test at 95 % confidence limit was used. The soil under Zabo farming system was found to be acidic in reaction and high in organic matter. The available nutrient status and micronutrients were higher in cultivated soil i.e. terrace and valley soils, compared to hilltop forest soil. The grouping/clustering behavior was observed by principle component analysis (PCA). The PCA plots clearly showed three distinct clusters i.e. the cluster of hilltop forest site is separated from the two clusters of cultivated sites of 10 village of Zabo farming sites along the PC axis-1 that showed that maximum variability ranged from 30.4-40.7%. The two clusters of cultivated sites were mainly separated along PC-axis-2 that indicated range from 13.5-15.7%. For comparison with reference sites Amoeba Plot scaled to 100 percent was used. The Amoeba plot design results highlighted that in depth (0-15cm) OC, N, P, DTPA-Cu, Zn, Mn, Ca+Mg, K, Na, BS, BD, MWHC, clay, sand were more pronounced, whereas in 15-30 cm depth, EC, P, DTPA-Cu, Mn, RSAl, exchangeable Ca+Mg, exchangeable K+, exchangeable Na+, BS, MWHC and clay was more pronounced compared to other parameters. Soil quality index of 0-15 cm depth was Middle Khomi (115.71%) > Kikurma > Chizami > Lower Khomi > Sakarba > Porba > Losami > Tetsumi > Upper Khomi>Pholami (105.35%), whereas in 15-30 cm depth, it was Losami (115%) > Chizami > Porba > Tetsumi > Kikurma > Middle Khomi > Upper Khomi > Sakarba > Lower Khomi > Pholami (80%). SQI values indicated that soil quality in maximum village of cultivated soil of Zabo farming sites was relatively higher than of hilltop forest site.