DISTRIBUTION AND RELATIONSHIP PATTERN OF SOIL PROPERTIES AND ORGANIC CARBON STOCKS UNDER APPLE GROWING ECOSYSTEMS IN TEMPERATE HIMALAYAS

Understanding the relative distribution and relationship pattern of basic soil properties and soil organic carbon (SOC), we quantified and characterized the SOC stocks and labile SOC pools along with depth and altitudinal gradients as well as studied their mutual relationship pattern under ecosystems of apple orchards in three physiographic altitudinal gradients of temperate Kashmir. From twenty four representative apple orchards in three selected altitudinal gradients, forty eight composite soil samples collected from two soil depths were analyzed according to the prescribed standard procedures. Analysis of the results showed that among physico-chemical properties, soils observed moderately acidic to slightly alkaline pH (6.62−7.40) varying significantly with depth while as cation exchange capacity (CEC) recorded significant increase from surface to sub-surface depth (13.3−17.5 Cmolp+kg-1). For soil separates only clay (%) content observed significant variation between depths. In general, the coefficient of variation (CV %) between soil depths exhibited maximum range for clay fraction (28.0−43.4%) followed by CEC (24.5-37.8%) and EC (20.6−31.4%). The soils of orchards located in higher altitudes represent significantly higher SOC fraction by a margin of 364% and 295% than corresponding mid and lower altitude ones; surface soils by 32% and 68% than sub-surface layers respectively. Significantly higher proportion of SOC stocks was recorded ranging between 32.1 to 94.6 Mg ha−1 with distinct depth variation (CV=15.7−44.4%). For stratification ratio (SR) of SOC, the values vary from 2.75 to 3.96 along the altitudinal gradient. Among labile carbon fractions, LBC recorded significantly higher fraction (0.78 to 4.90 g kg-1) reflecting margin of 146.15% in upper soil layers than lower layers followed by MBC (94.65%) and POC (102.3%) respectively. LBC (15.4−27.2%) represents maximum variability with depth followed by MBC (7.7−20.6%) whereas as POC observed least significant variation (CV=7.2-15.5%). Regarding relationship studies, pH observed significant and positive correlation with clay and all SOC fractions except POC while as clay content showed significantly positive correlation with CEC (0.596*), SOC (0.544*), TOC (0.512*) and MBC (0.620*). SOC was best correlated with LBC (0.834%) and MBC (0.650%) whereas TOC showed positive and significant correlation (p=0.05) with SOC (0.579*) and POC (0.481*). All fractions of C revealed significant and positive correlation with MBC. On the basis of these results, effective measures in terms of appropriate nutrient source managements and efficient carbon sequestration practices can be designed and implemented.