Seasonal variations in C and N fractions under tree-based cropping systems in typic ustochrepts

Abstract

The growing of tree on cultivated land along with agricultural crops is quite common in sub-montane region of northwest India for dual purpose. It enhances the soil fertility and also provides assurance to farmers in case of extreme conditions. A study was conducted to monitor the influence of season on the content of soil organic carbon and nitrogen under four cropping systems. The experiment was carried out in foothills of lower Himalayas. Soil organic carbon (SOC), particulate organic carbon (POC), aggregates associated carbon (AAC), total nitrogen (TN), available nitrogen (AN) and aggregate associated nitrogen (AAN) were determined from 0 to 15 cm and 15–30 cm soil depths under four cropping systems comprising maize–wheat, agro-horticulture, agroforestry 3-year old and 6-year old plantation. The data so obtained was analyzed by using completely randomized design—factorial design at LSD (P < 0.05). The seasonal variations in C and N fractions were significant. The SOC and TN content were higher on an average 7.3 mg g−1 and 0.86 Mg ha−1 in March than those determined in November (4.9 mg g−1 and 0.45 Mg ha−1). This is due to higher leaf litter fall in winter months (December–February). Lower content of C and N fractions were found in autumn season due to highest rainfall received during the monsoon period (May–October) in this region. This caused the aggregate disruption, washing of SOC and nitrogen loss. The C and N fractions also varied significantly with respect to soil depths and cropping systems and were highest under agroforestry system. The agroforestry systems showed greatest seasonal variation than agro-horticulture and mono-cropping system.