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Soil organic matter (SOM) in any agro-ecosystem is regulated by interaction of factors that determine its formation and promote decomposition, with a relative importance as: management > climate > biota > topography = parent material > time. Different land use practices under diverse climatic conditions in Hassan district (Karnataka) were selected for the study. Land use systems receiving frequent biomass additions through litter viz., Forest systems (both natural and manmade) and coffee plantations were observed with surface organic layer with higher SOC (10.6-13.2) content (g kg -1 soil). Agricultural systems mainly paddy, potato, vegetable, coconut and mulberry systems sparse OM additions were observed with reduced and lower SOC status (4.6-6.6). Humic acid (HA) and fulvic acid (FA) under these land use systems were dependent on land management i.e. source, form, amount, rate of organic materials added to soil. The HA fraction ranged from 0.2 g 100 g-1 soil in soils of coconut and paddy systems to 0.4 g 100 g-1 soil in natural forests. Quantitatively higher HA in forest and coffee systems was observed than agricultural systems. Proportionately to total SOM content (%), the HA was higher in agricultural soils (24.4-28.0) than coffee and forest soils (19.6-20.7). The systems with tree vegetations (forests and coffee) recorded higher proportions of FA (29.4-30.5) than agricultural systems like potato (26.5) and paddy (27.4). Forest systems with litter biomass additions (fresh organic materials) were with higher FA content while, agricultural systems receiving with almost decomposed OM (FYM) indicated higher HA than FA.

Slag-based gypsum (SBG) is a unique synthetic gypsum which is alkaline in nature, besides calcium (Ca) and sulphur (S); it contains appreciable amounts of iron (Fe), silicon (Si), phosphorus (P) and zinc (Zn). In this study, we evaluated the efficacy of SBG as a source of S, Ca and Si for groundnut in comparison with natural gypsum (NG). The effect of different levels and time of application of SBG on soil fertility and yield and quality of groundnut were also studied. Field experiments were conducted with five treatments which includes two levels of SBG (500 and 625 kg ha −1) applied as basal and basal + split and one level of NG (500 kg ha −1) applied as basal. Basal and basal + split applications of SBG significantly increased the pod and haulm yield of groundnut, pH, electrical conductivity and plant-available nutrients in post-harvest soil. However, N:S ratio, kernel and protein yield and oil content did not vary with SBG application. Applied S, Ca and Si as SBG and their uptake were positively correlated with plant-available S, Ca and Si and pod, oil and protein yield of groundnut, respectively. Basal and basal + split applications of SBG resulted in a similar effect on soil fertility and yield and quality of groundnut. Findings from this study show that SBG can be a potential alternative for NG as a source of S, Ca and Si for groundnut production. Among the treatments, basal and basal + split applications of 625 kg SBG ha −1 substantially improved the fertility of soils and yield and quality of groundnut.

The present study was conducted to assess the impact of different land-use systems on major nutrient status viz: Nitrogen, Phosphorus and Potassium in soils of central part of Western ghat, Karnataka. The land use types include both manmade systems (Agriculture: paddy; Horticulture: coffee, are canut, tea and banana); forest plantation (accacia and teak) and natural systems (Evergreen, semi-evergreen and grassland). In each land use systems, samples were collected from two depths (0-15 cm and 15-30 cm) at 20 locations during pre-monsoon and post monsoon period. Soil samples were analyzed for available nitrogen, available phosphorus and available potassium. The results revealed that available nitrogen content in surface soil was significantly higher (394.55 kg ha -1 ) than that of subsurface soil (330.57 kg ha -1 ). Among manmade land use systems, available nitrogen content was significantly higher in coffee (435.82 kg ha -1 ) followed by in soils under banana 404.40 kg ha -1 . Similarly, natural system the available-N content was in the range of 294.97 to 376.55 kg ha -1 with minimum in grassland and maximum in semi-evergreen forest. Available-P varied significantly among different land use systems. The highest available-P content was recorded in soils under coffee (29.31 kg ha -1 ) followed by evergreen forest (28.37 kg ha -1 ), semi-evergreen (27.26 kg ha -1 ) and other systems. The available-P was least in grassland (20.28 kg ha -1 ). The available K 2 O content in soils under paddy was 299.42 kg ha -1 and it was significantly lower than other systems but was at par with those observed in grassland (311.01 kg ha -1 ), acacia (321.01 kg ha -1 ) and teak system (329.86 kg ha -1 ). These results are indicated that well-managed horticultural system in general and coffee in particular had better soil fertility which is comparable to that found in natural forest system.

Background: Slag based gypsum (SBG) is a value-added product of iron and steel industry. Application of gypsum as source of calcium and sulphur for groundnut cultivation is common practice and mainly applied during peg initiation stage of groundnut. However, its effect is mainly influenced by the type of soil and dissolution of gypsum, which facilitates the yield and quality of groundnut. Hence, field experiments were conducted to know the effect of application of different rates of SBG as basal and split application on soil properties, yield, quality, nutrient use and uptake efficiency of groundnut in acidic soil. Methods: This study contains of seven treatments which includes recommended dose of fertilizer (RDF) with three levels of SBG (375, 500 and 625 kg ha-1) was applied as basal and split and 500 kg natural gypsum (NG) ha-1 was applied as basal dose according to package of practice (POP) of University of Agricultural Sciences, Bangalore by using randomly complete block design (RCBD) at Agricultural Research Station, Balajigapade during kharif 2018 and 2019. Result: The pooled data of two field experiments on groundnut revealed that application of RDF + 625 kg SBG ha-1 as 50% at sowing + 50% at peg initiation stage recorded higher pod (28.01 q ha-1), haulm (54.46 q ha-1), kernel (20.59 q ha-1), protein (89.70 q ha-1) and oil (7.06 q ha-1) yield when compared to other treatments. There was an increase in pod, haulm and oil yield of groundnut by 11.62, 20.59 and 17.99%, respectively with the split application of 625 kg SBG ha-1 (50% at sowing + 50% at 30 DAS) over NG applied treatments. Split application of SBG significantly increased the availability of nutrients in post harvest soils than basal application. Significantly higher S and Ca nutrient use efficiency (33.98 and 28.93 kg produce/kg S and Ca utilized, respectively) and uptake efficiency (0.39 and 1.29 kg kg-1, respectively) was recorded with the split application of SBG @ 375 kg ha-1.