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This study on soil carbon dynamics provides valuable insights for sustainable agricultural practices, optimizing crop productivity and environmental sustainability in maize-based cropping systems. The present study aimed to find out the soil characteristics and carbon dynamics in maize-based cropping systems in the Western zone of Tamil Nadu, India. Soil samples from six cropping systems were analyzed for bulk density, sand, silt, clay content, pH, available nutrients (N, P, K, Zn), total organic carbon (TOC), oxidizable organic carbon fractions, microbial biomass carbon (MBC), and carbon pools. The distribution of oxidizable organic carbon fractions varied among cropping systems and soil depths. The easily decomposable and moderately labile fractions were highest in the maize-black gram system, while the recalcitrant fraction showed variations across cropping systems. The active carbon pool (Cf1 + Cf2) was highest at 2.53 g kg-1 in the maize-blackgram system, while the passive carbon pool (Cf3 + Cf4) was also highest at 3.79 g kg-1 in this system. The study also assessed the carbon stock and microbial biomass carbon. TOC content decreased with depth, with the highest values observed in the topsoil. The maize-black gram system had the highest TOC content at all depths. MBC content followed a similar pattern, with the highest values in the topsoil and the maize-black gram system. These findings provided insights into the soil characteristics and carbon dynamics in maize-based cropping systems in the study area. The long-term integration of maize cultivation with blackgram demonstrated significant enhancements in organic carbon levels, TOC content, microbial biomass carbon (MBC), and both passive and active carbon pools characterized by rapid turnover rates. [ABSTRACT FROM AUTHOR]

Soil organic carbon (SOC) is a potential indicator of soil quality and ecosystem sustainability. The present study aimed to evaluate SOC pools under major cropping systems of Mayiladuthurai district of Tamil Nadu. The composite samples were collected from two depths (0-15 and 15-30 cm) by stratified random sampling and were analysed for pH, EC (Electrical conductivity), C fractions, inorganic carbon and permanganate oxidisable carbon by standard procedures. The SOC content under different land use was in the order of Forestry > Rice – pulses > Rice – cotton > Sugarcane > Uncultivated. The mean SOC content of the study area was 12.58 Mg ha-1, where the majority of the area falls under low to medium rating of SOC. Hence, cultivation practices should incorporate activities that increase SOC to maintain soil quality. SOC was positively correlated with fractions of carbon – CVL (r = 0.37**), CL (r = 0.65**) and CLL (r = 0.58**), indicating changes in land use would affect the carbon dynamics of the ecosystem. The root biomass, aeration status, microbial activity, nutrient reserves and inherent soil characteristics influenced SOC to decrease with depth. The PCA analysis revealed that the variation in carbon dynamics of the study area was influenced by SOC, CLC, CLL and non-labile carbon due to differences in land management practices. Therefore, such soil management practices will be a powerful tool to sequester carbon, which supplements climate change mitigation. [ABSTRACT FROM AUTHOR]

Soil carbon mineralization is vital for carbon sequestration but affected by factors like soil type and residue quality. Understanding the process and factors is still incomplete, including the interplay between soil properties and organic residues and the need for accurate kinetic models. Research faces significant challenges in describing carbon mineralization dynamics. The present study aimed to investigate carbon mineralization in three soils located in Tamil Nadu, India (S1, S2 and S3) that possess distinct textures. The study also focused on the effects of five different plant residues (Rice, maize, sugarcane, cotton and turmeric) on carbon mineralization in these soils. Incubation experiments were conducted for 150 days, and CO2 evolution was measured at different time intervals of 7, 10, 15, 30, 60, 90, 120 and 150 days. The performance of three kinetic models (Zero order model, exponential kinetic model and first order model) was also evaluated in predicting carbon mineralization using experimental data. The results showed that the rate and extent of carbon mineralization varied significantly among the different soils and residues. The highest carbon mineralization was observed in rice (989.02 µg C/g/day) and maize (966.53 µg C/g/day) residue, while the lowest was in sugarcane (752.09 µg C/g/day) residue. Among the kinetic models, the first-order kinetic model provided the best fit for all treatments (R² =0.98). The findings suggest that soil texture and residue quality play crucial roles in carbon mineralization. The first order kinetic model can be useful for predicting carbon mineralization in different soil-residue systems. These results have implications for managing soil carbon sequestration and mitigating climate change. [ABSTRACT FROM AUTHOR]

An experiment was conducted to study the impact of water logging and addition of organic amendments on green house gas (GHG) emissions in a saline soil. The treatments comprised of water levels maintained at three levels viz., complete saturation, 10 cm and 15 cm below the soil surface. Organic amendment at the rate of 7.5 t ha-1 was added. Gas samples were collected at periodic intervals and analysed. The results revealed that CO2, N2O and C2H2 emissions were lowe under a water logged condition and were found to be higher at water levels 10 cm / 15 cm below the soil surface. There was an increase in emissions from 100 to 400 mg kg-1 at 7 days after incubation (DAI). Methane emission was found to be higher in completely saturated soil. Soils at 10 cm water level and amended with the organic material registered a higher value of soil microbial biomass - C of 1320 mg kg-1. Emissions of GHG were enhanced with the addition of organic material. This suggests that lack of C substrate is the dominant limitation for GHG emissions on saline soil. Lower q CO2 values in water logged soils indicate low microbial activity. [ABSTRACT FROM AUTHOR]

A pot culture experiment was carried out with the redgram var. CO(Rg)7 at Tamil Nadu Agricultural University, Coimbatore. The soil used for the experiment was red, calcareous, sandy loam which belongs to the soil series Palladam (TypicUstropept). The experiment soil was medium in available N (285 kg ha-1), high in available P (26.75 kg ha-1) and K (287 kg ha-1). The soil was deficient in DTPA-Fe (4.80 mg kg-1), DTPA-Mn (0.25 mg kg-1), DTPA-Zn (0.15 mg kg-1), DTPA-Cu (0.22 mg kg-1), and sufficient in hot water soluble B (0.75 mg kg-1). The experiment was laid out with eleven treatments in a completely randomised design (CRD) replicated thrice to study the effect of foliar application of multinutrients on the yield, quality, uptake and soil nutrient status of redgram. In the treatments of foliar application with different combinations of complex, micronutrient and chelated micronutrient fertilisers at different stages, application of 0.5% KNO3 + 2% DAP + micronutrient spray along with soil application of 100% recommended dose of NPK (T7) recorded the maximum value of yield attributes. Quality parameters such as seed protein content and seed total free amino acid content were enhanced by the foliar application of 0.5% KNO3 + 2% DAP + micronutrient spray. Application of 100% RD NPK and foliar spraying of 0.5% KNO3 + 2% DAP + micronutrient recorded the highest macro and micro nutrient uptake which was followed by the treatments that received 100% RD NPK and foliar spray of 0.5% MAP + 0.5% KNO3 + micronutrients and 100% RD NPK and foliar spray of 0.5% KNO3 + 2% DAP + chelated micronutrients. Availability of N, P, K, Fe, Mn, Zn, Cu and B contents in soil at different stages was significantly influenced by the various foliar applications. The Chlorophyll 'a', 'b' and total chlorophyll contents were found to be the highest in the treatment that received 100% RD NPK + foliar spray of 0.5% KNO3 + 2% DAP + micronutrients (T7). [ABSTRACT FROM AUTHOR]

Field trials were conducted in agroforestry system involving multipurpose tree species and fodder crops to assess the biomass production in Acacia leucopholea, Ailanthus excelsa, Tectona grandis, Gmelina arborea, Erythrina indica, Pongamia glabra and Thespesia populenea based silvipasture system. The results revealed that A. leucopholea + Cenchrus Ciliaris gave the highest LER of 1.13. Under 15 years old A. excelsa plantations, fodder cow pea recorded the highest fodder yield of 7.08 t ha-1 with LER value of 0.84. Desmanthus virgatus was found to be a compatible fodder crop for teak plantations of 10 years old and guinea grass recorded the highest green fodder yield of 3.91 t ha-1under pungam based silvipasture system. In all the silvipastoral systems, irrespective of the tree component, grass fodder recorded the highest RYT followed by legume fodder. [ABSTRACT FROM AUTHOR]

Field experiments were conducted in two different agro-climatic zones during kharif 2011 at Tamil Nadu Rice Research Institute, Aduthurai and Wetlands, TNAU farm, Coimbatore to study the effect of customized fertilizers on yield and soil properties of lowland rice ecosystem. Two formulations of customized fertilizers viz., N: P: K mixture (CF I) and N: P: K: Zn mixture (CF II) have been developed based on the blanket recommendation (BR) of straight fertilizers being followed in Tamil Nadu. Three levels of CF I and CF II viz., 50%, 75% and 100% of RDF were compared with 100% RDF through straight fertilizers. The results revealed that application of 100% RDF in the form of CF II increased the productive tillers (21 nos.), panicle length (27.70 cm) and number of filled grains per panicle (203 nos.). Application of 100% RDF in the form of CF II recorded the highest grain yield of 6878 kg ha-1 followed by the application of 100 % RDF in the form of CF I + 25 kg Zn SO4 ha-1 ( 6622 kg ha-1). Per cent increase in yield of 22.2 per cent over the application of straight fertilizers was recorded due to the application of 100 % RDF in the form of CF II. [ABSTRACT FROM AUTHOR]

Field experiments were conducted in two different agro-climatic zones during kharif 2011 at Tamil Nadu Rice Research Institute, Aduthurai and Wetlands, TNAU farm, Coimbatore to study the effect of customized fertilizers on yield and soil properties of lowland rice ecosystem. Two formulations of customized fertilizers viz., N: P: K mixture (CF I) and N: P: K: Zn mixture (CF II) have been developed based on the blanket recommendation (BR) of straight fertilizers being followed in Tamil Nadu. Three levels of CF I and CF II viz., 50%, 75% and 100% of RDF were compared with 100% RDF through straight fertilizers. The results revealed that application of 100% RDF in the form of CF II increased the productive tillers (21 nos.), panicle length (27.70 cm) and number of filled grains per panicle (203 nos.). Application of 100% RDF in the form of CF II recorded the highest grain yield of 6878 kg ha-1 followed by the application of 100% RDF in the form of CF I + 25 kg Zn SO4 ha-1 (6622 kg ha-1). Per cent increase in yield of 22.2 per cent over the application of straight fertilizers was recorded due to the application of 100% RDF in the form of CF II. [ABSTRACT FROM AUTHOR]