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Soil organic carbon stock is an important universal land degradation indicator. Owing to the depletion in soil nutrients, the pace of land degradation has increased in the Western Ghats of South India. To understand the changes in surface and subsurface soil organic carbon stocks and vulnerability to land degradation upon land use change, a study was carried out along the natural forest and coffee plantation ecosystems of Western Ghats in South India. The study sites were located in Chikmagaluru of Karnataka and Wayanad and Idukki districts of Kerala. Soil organic carbon stocks (SOC) at the surface (0–30 cm) were higher, 9.10 t C ha−1 and 7.49 k t C ha−1 in forest soils of Chikmagaluru and Idukki, respectively, and the subsurface (30–100 cm) SOC stocks were higher in the coffee plantation ecosystems, 9.11, 9.87, and 8.41 t C ha−1, respectively, in Chikmagaluru, Wayanad, and Idukki. Vulnerability analysis revealed that Chikmagaluru forest (0.57) and coffee (0.51), Wayanad forest (0.58) and coffee (0.55) land uses were low, and both the land uses in Idukki were medium in the status of land degradation with scores of 0.65 and 0.60, respectively, in forest and coffee ecosystems. The difference in the status of land degradation was mainly because of changes in soil reaction, surface, and subsurface SOC stock. An increase in soil pH, CEC, and available nutrients upon conversion to coffee plantation along with increased subsurface carbon storage have confirmed the restorative properties of coffee land use even after conversion from natural forests. [ABSTRACT FROM AUTHOR]

Soil quality assessment is important for arable land, particularly in the vicinity of urban areas. The research was carried out to determine the quality of soil that has been farmed for different land uses. Geo-referenced 200 surface soil samples were collected from agriculture, horticulture, flower and plantation land-uses, and were analyzed for soil texture and nutrients, of which pH, OC, N, P2O5, K2O, Mn, Cu, Ca, and dehydrogenase activity (DHA) were found statistically significant and were chosen for principal component analysis (PCA). Based on the level of significance from PCA only five variables (pH, K2O, Cu, Ca, and DHA) were retained for minimum data set and linear scoring functions were used to provide unit-less scores for the selected data sets, which were then integrated into a soil quality index (SQI). Plantation land use had the lowest (SQI) of 0.51, whereas agriculture land use had the highest SQI (0.55) and was comparable to flower and horticultural land uses (0.53). The SQI of agriculture land was found better than the plantation land use in nearly all of the quality indicators evaluated. As a result, implementing management measures that improve soil quality, such as OC, is critical for sustainable agricultural production. [ABSTRACT FROM AUTHOR]

Critical limit (CL) determination of zinc (Zn) is much more important to assess the response of crop to its application in soils and for crops actual fertilizer requirement. This experiment was conducted at University of Agricultural Sciences, Bangalore in sandy clay loam texture soils. Based on the results of the pot culture experiment, the critical limits of DTPA, AB-DTPA, Mehlich-3, tomato plant and tomato fruit are 1.12, 1.20, 2.15, 34 and 58 mg kg−1, respectively. Tomato was highly responded to Zn application in soils below the critical limit whereas soils with Zn greater than 1.12 mg kg−1 did not respond much. For the confirmation of pot culture results, two field experiments were carried out during 2017–18 with different Zn treatments one in high and other in low zinc soils. The study concluded that for both low zinc and high zinc soils external application of zinc through Recommended dose of fertilizers (RDF) + ZnSO4 @ 30 kg ha−1 as soil application (SA) + foliar application (FA) @ 0.50% ZnSO4 and RDF + ZnSO4 @ 20 kg ha−1 as SA + FA @ 0.25% ZnSO4 significantly improved yield, nutrient concentration and uptake of nutrients, which helped in getting higher benefit cost (B:C) ratio of 4.74 and 4.96, respectively. This information is helpful in site-specific zinc nutrition in tomato and to enhance the productivity and profitability. [ABSTRACT FROM AUTHOR]

The variability of soil qualities across the coffee‐growing areas and consequences of conversion of forest to coffee plantations on soil qualities and sustainability in the Western Ghats of South India are evaluated in this study by assessing and studying the six representative pedons selected from Chikmagalur district in Karnataka and Wayanad and Idukki districts of Kerala taking into consideration of the agro‐ecological zones, they belong. Sixty sites were located for monitoring soil quality, of which 46 sites were located in coffee plantations of all agro‐climates and 14 in forests adjacent to coffee plantations in similar setting. Soil quality indicators were selected by carrying out principal component analysis (PCA) on measured soil attributes, which provided 4 PCs in both land uses with eigen values > 1 and explaining at least 5 per cent variance in data set. The indicators for coffee land use were pH, exch. Al and CEC and for forest land use, organic carbon, pH and exch. Al. These indicators were transformed into scores following linear scoring method and soil quality index was determined, on a scale of 0–1, using the weighting factors obtained from PCA. Soil quality index was high (0.836) for natural forest land use, while it was medium (0.634) for coffee land use. Results indicated that organic carbon, pH and exch. Al are the most powerful indicators of soil quality. Proper management of soil acidity in coffee plantations due to liming, pooling back of nutrients, fertilization effect and other anthropogenic interventions in them have helped in maintaining a near equal soil quality to that of natural forest, which can be made sustainable by adopting effective plantation management practices. [ABSTRACT FROM AUTHOR]