Effect of acetylene and ethylene gases released from encapsulated calcium carbide on growth and yield of wheat and cotton

Abstract

Calcium carbide (CaC2) is a rich source of the nitrification inhibitor acetylene (C2H2) and plant hormone ethylene (C2H4). C2H4 formed from biotic reduction of C2H2 released from CaC2 may accumulate in soil at physiologically active concentrations. Laboratory studies were conducted to evaluate the potential of encapsulated CaC2 for gradually releasing C2H2 and its product C2H4 in soil. The GC-FID analysis revealed that encapsulated CaC2 released a copious amount of C2H2 (up to 23700 nmol kg−1 soil), which was gradually reduced to C2H4 over a period of time via a strictly biotic reaction as no C2H4 was detected in CaC2-amended sterilized soil. Ammonium oxidation was suppressed by the encapsulated CaC2 indicating that C2H2 acted as a nitrification inhibitor. Results of pot trials conducted in the net house indicated that encapsulated CaC2 applied at 30 mg kg−1 soil significantly increased the number of tillers (up to 45.5%), root weight (up to 14.9%), straw (up to 32.8%) and grain yield (up to 37.3%) of wheat over the fertilizer application alone. In the case of cotton, the number of bolls, root, shoot and seed weight were also significantly increased in response to the application of encapsulated CaC2. Moreover, application of encapsulated CaC2 resulted in greater N-use efficiency (NUE) (up to 61.1%) by both wheat and cotton crops than that observed at the same rates of N fertilizer alone. These findings imply that CaC2 affects plant growth through hormonal action of C2H4 as well as improved NUE; however, the latter factor might be a relatively more contributing. It is desirable that CaC2 is formulated for gradually slow release of C2H2 and C2H4 in soil air.