Effect of temperature on soil organic carbon mineralization in aggregate fractions under different tillage and nutrient management Lenka Sangeeta1,*, Malviya Sunil Kumar2, Lenka Narendra Kumar3,**, Saha Jayanta Kumar1, Yadav Dinesh Kumar1 1Environmental Soil Science, ICAR-Indian Institute of Soil Science, Nabibagh, Bhopal, Madhya Pradesh, India 2Department of Soil Science and Agricultural Chemistry, RAK College of Agriculture, Sehore, Madhya Pradesh, India 3ICAR-Indian Institute of Soil Science, Nabibagh, Bhopal, Madhya Pradesh, India *Corresponding author email id: sangeeta_2@rediffmail.com
**nklenka@rediffmail.com
Abstract Understanding the factors controlling the mineralization of soil organic carbon (SOC) in aggregate fractions is important in the context of changing global climate. Therefore, a laboratory incubation study was undertaken, to study the effect of temperature on SOC mineralization in different aggregate size fractions under different tillage and nutrient management. The soil (0-15 cm) for the present study was collected after eight years of long-term experiment under conservation tillage and nutrient management in the soybean-wheat system of Vertisol. The treatment consisted of two levels of tillage (no tillage, NT and reduced tillage, RT) and nutrients (NPK, T1 and NPK + FYM, T2). The 4 mm sieved soil was dry sieved by passing through nest of 2 mm and 0.250 mm sieve to obtain aggregate size class > 2 mm (large macroaggregate), 2-0.250 mm (small macroaggregate) and < 0.250 mm (microaggregate and silt + clay size). Each aggregate fraction and bulk soil (20 g) were incubated in 300 ml glass jars in replication of three at 25, 35 and 45 °C (±1°C) for 122 days in three incubators. Soil respiration was measured at regular interval and the cumulative soil respiration was calculated from the observed respiration rates at regular interval. The results of the experiment showed the cumulative mineralizable C from aggregate fraction was higher by 30% in RT than NT with the greatest differences occurring in the microaggregate size classes (<0.250 mm) across all temperatures in NPK treatment. However, there was no difference in cumulative mineralizable C between NT and RT treatments in NPK + FYM treatment at 35 and 45°C. The cumulative SOC mineralization increased significantly with increase in incubation temperature. The Q10 values of soil C mineralization were significantly affected by the main effects of land management, aggregate size class and their interactive effect. The Q10 values of soil C mineralization were greater for the low temperature ranges 25-35°C than the high temperature range 35-45°C. In RT treatment Q10 was lower than NT treatments and application of FYM increased the Q10 of soil C mineralization in both RT and NT. Top Keywords Temperature sensitivity (Q10), Tillage, Nutrient, SOC mineralization, Aggregate fractions. Top |