Vertical distribution analysis of soil organic carbon and total nitrogen in different land use patterns of an agro-organic farm

Abstract

While the quantity of soil organic carbon and nitrogen are used as indices of soil quality assessment and sustainable land use management, soil microbial activity is also a sensitive indicator of soil quality. Though the dynamics of carbon and nitrogen in terrestrial ecosystem can be largely affected by macro factors such as climatic conditions, local micro environmental factors such as land use history, plant functional type and management practices also play an important role in this regard. The present study was aimed at assessing and analyzing different types of land use patterns so as to understand their influence on the depth wise distribution of soil organic carbon (SOC), total nitrogen (TN) and microbial activity under the same management practices. The investigation was carried out in an organic farm located at Anand, Gujarat, India. Three different types of land use patterns viz., (i) fodder grass raising land, (ii) teak woodland, and (iii) wheat-pearl millet cropland were selected. Vertical (0–100 cm depth) variation in soil biophysical properties was recorded. Analysis of variance showed SOC (%) and TN (%) varied significantly (P < 0.001) with land use patterns (LU), depth (D), and LUxD. It was found that at all three land use patterns SOC and TN were highest at upper layer (0–10 cm) then decreased towards deeper layers (up to 40 cm) and then again increased with depth (40–100 cm) in soil profile. Highest values of SOC (%) and TN (%) (1.02% and 0.08% respectively), were reported in wheat-pearl millet cropland at 0–10 cm depth. Use of organic amendment made a great impact on SOC (%) in wheat pearl-millet cropland throughout the soil profile. We found almost same quantity of SOC (%) at 0–10 cm and 80–100 cm in teak woodland and grass raising land. The microbial biomass (carbon and nitrogen) and dehydrogenase activity were also found to be highest at upper layer (0–10 cm) in wheat-pearl millet cropland (418.2 µg/g, 52.9 µg/g and 104.05 TPF µg/g respectively) as compared to other two types of land use patterns. A significant positive correlation was observed between soil organic carbon and total nitrogen with microbial biomass and dehydrogenase activity at all three land use patterns. Our findings suggest that changes in land use pattern and management practices make a significant impact on vertical distribution of SOC and TN. Accurate investigation of SOC and TN storage at regional levels is important for detecting changes in carbon and nitrogen sequestration potentials induced by land use changes over a period of time to enable the rebuilding of SOC and TN in agro-ecosystems.