Earlier events :: 2014 :: STUDENT Talks

Seasonal variations in nitrogen transformations: Comparing organic and conventional agricultural practices

Presented by
Manjunatha H C
Indian Institute Of Science
Manjunatha H C, Mahesh Sankaran

Introduction: What conservation problem or question does your study address?

Intensive farming practices to increase the productivity is a havoc to the ecosystem. Sustainability in agriculture is of major concern in order to reduce the impact of conventional agriculture on ecosystem services. N transformations in soil is an essential ecosystem service and it determines the plant growth & productivity. However, the effect of intensive agriculture on N transformations & the role of sustainability in agriculture to reduce its impact is unclear.

Methods: What were the main research methods you used?

This study was conducted in coffee agro-forests of Kodagu. We compared the effect of two different farming practices viz organic and conventional on the rate of N transformations in soil. For this, we incubated the soil in both kinds of farms using buried bag method for a period of 30 days. At the beginning of incubation and post incubation, inorganic N was extracted from soil using calcium chloride solution. Extracts were analysed for ammonium and nitrate using continuous flow auto analyser. The N transformation rate in soil was determined as differences in inorganic nitrogen between incubated and control soil. The experiment was repeated from January to December in 2012 to understand the effect of seasonal variations on N transformations in soil in two different farming systems. Analysis was done using linear mixed effect models to test the effect of two different farming practices and temporal pattern on N transformations in soil.

Results: What are your most important results?

Conventional farms showed low rate of N transformations compared to organic farms. These two different types of farming practices showed a clear seasonal trend in N transformations. N transformations did not vary between organic and conventional farms during dry season, but organic farms showed significantly high rate of N transformations during wet season. High rates of annual N mineralization have been found in organic farms as compared to the conventional ones.

Discussion: What are your important discussion points and what is the relevance of your results to conservation (if any)?

Results demonstrate that intensive farming practices reduce the efficiency of an essential ecosystem service - N transformations in soil. Due to input of high amount of fertilizer N, conventional farms showed high amount of inorganic N in the soil compared to organic farms. The high amount of N and less organic matter in the soil could potentially lead to increase in soil acidity, erosion, reduced biodiversity and increase in downstream eutrophication and pollution.