Effect of Organically Grown Cropping Systems on Soil Properties and their Correlation with Carbon Pools

Abstract

Organic agriculture is gaining significance for its benefits in crop diversity, sustainability, and soil organic carbon enhancement. Considering these advantages, a study was conducted during Kharif 2021-22 at the Research Farm, Centre for Organic Agriculture Research and Training, Department of Agronomy, Dr. Panjabrao Deshmukh Krishi Vidyapeeth, Akola, to evaluate the effect of organically grown cropping systems on soil organic carbon dynamics and soil properties in vertisols. The experiment, laid out in a Randomized Block Design (RBD), included seven treatments: T1 (sole Cotton), T2 (Cotton + Sunhemp, 2:1), T3 (Cotton + Blackgram, 2:1), T4 (Soybean + Pigeonpea, 3:1), T5 (Blackgram - Chickpea), T6 (Greengram + Sorghum, 2:1), and T7 (sole Sunhemp), replicated three times. Nutrients were supplied through FYM and vermicompost (50% N each), with phosphorus supplemented by Phosphate Rich Organic Manure (PROM). Results indicated that the T2: Cotton + Sunhemp system recorded the lowest bulk density (1.42 Mg m-3), highest hydraulic conductivity (0.76 cm hr-1), and mean weight diameter (0.73 mm), reflecting improved soil structure. Also, soil pH (8.04-8.11) and electrical conductivity (0.13-0.15 dS m-1) decreased compared to initial values (8.12 and 0.16 dS m-1). The T2: Cotton + Sunhemp system also showed significant improvement in soil organic carbon (6.09 g kg-¹) and reduction in calcium carbonate 3.69% to 3.48%. Nutrient availability was significantly highest in the T4: Soybean + Pigeonpea system, with available nitrogen (209.27 kg ha-1), phosphorus (22.28 kg ha-1), and potassium (354.26 kg ha-1). CO2 evolution (35.4 mg 100 g-1 soil) and Dehydrogenase activity (47.66 μg TPF g-1 24 hr-1) was significantly highest in T2: Cotton + Sunhemp system. The T2: Cotton + Sunhemp system also showed the highest organic carbon (6.09 g kg-1), with very labile C (4.04 g kg-1), labile C (1.29 g kg-1), and less labile C (0.93 g kg-1) being highest in surface soil (0-20 cm). Non-labile C (5.13 g kg-1) was highest in T1: sole Cotton. Correlation analysis highlighted the importance of organic carbon, showing positive relationships with hydraulic conductivity, mean weight diameter, CO2 evolution, and dehydrogenase activity, while negatively correlating with bulk density and calcium carbonate. The study concludes that organically grown cropping systems, particularly T2: Cotton + Sunhemp system, significantly enhance soil health, carbon sequestration, and nutrient availability, supporting sustainable agriculture.