Comparative effects of organic and inorganic fertilizers on soil organic carbon under sub-humid southern plain and Aravalli hills of Rajasthan

A field experiment was conducted during rabi 2023–24 and 2024–25 at the Instructional Farm, Rajasthan College of Agriculture, Udaipur, to evaluate the comparative effects of long-term organic and inorganic fertilization on soil organic carbon (SOC) under a maize–wheat cropping sequence. The experiment was laid out in a randomized block design with 12 nutrient management treatments, comprising sole chemical fertilizers, organic manures and their integrated combinations. The results revealed that SOC content was significantly enhanced under organic and integrated nutrient management practices compared to sole chemical fertilization and unfertilized control. Application of FYM @ 20 t ha⁻¹ (T₈) recorded the highest SOC values (0.985–0.987%), showing nearly an 86% increase over control (0.530%), followed by NPK + FYM 10 t ha⁻¹ (T₇: 0.942%) and FYM 10 t + 100% NPK (T₆: 0.921%). Balanced fertilization with micronutrients and biofertilizers resulted in moderate improvements in SOC, whereas imbalanced fertilization treatments such as 100% N and 100% NP showed limited effectiveness. Pooled analysis across years confirmed that continuous application of FYM, either alone or in combination with NPK, was most effective in sustaining and building soil organic carbon. The study highlights the critical role of organic and integrated nutrient management in enhancing soil carbon stocks, thereby improving soil health and sustainability of wheat-based cropping systems in the sub-humid southern plain and Aravalli hills of Rajasthan.