Effect of green manure Sesbania sesban and nitrification inhibitor encapsulated calcium carbide (ECC) on soil mineral-N, enzyme activity and ... from: European Journal of Soil Biology]

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Description:
Green manure Sesbania sesban (S. sesban) and the nitrification inhibitor encapsulated calcium carbide (ECC) have been used to improve N supply and management in rice-wheat production systems in India. However, the ecological impact of combined use of these materials is largely unknown. We conducted a net-house pot culture experiment for 2 years, to investigate the effects of S. sesban and ECC on mineral N availability (NH"4^+ and NO"3^-), soil enzyme activities (dehydrogenase and nitrate reductase) and populations (MPN) of nitrifying organisms under a rice-wheat cropping system. Green manure S. sesban and ECC (+ECC or -ECC) were applied along with urea in various combinations to hybrid rice under flooded conditions. For wheat, it was urea alone or urea+ECC. Soil samples were studied at 10 days after top dressing, i.e. 40 days after rice transplanting and 35 days after wheat sowing, for above characteristics. The mineral-N in soil revealed the significant effect of combined use of S. sesban and ECC to enhance NH"4^+ and total mineral-N (NH"4^++NO"3^-) contents. Dehydrogenase and nitrate reductase activities and population (MPN) of ammonia oxidizing bacteria (AOB) revealed a significant reduction in soils, whereas nitrite oxidizing bacteria (NOB) remained almost unaffected (P>0.05) in response to application of ECC with S. sesban and urea. Our results suggest that slow release of acetylene (C"2H"2) from ECC has reduced ammonia mono-oxygenase with reducing population of AOB, and has the potential to retard the enzyme activities in favor of C and N conservations in a semi-arid agro-ecosystem.