Organic matter transformations in soils

Summary

The kinetics of carbon and nitrogen mineralization in soils amended with different organic materials was investigated at different periods of incubation lasting for 30 weeks. The data indicated that the decomposition of organic matter in soils is controlled by two simultaneously occurring superimposed first-order kinetic reactions. Based on cumulative C or N mineralization-t^1/2 relationships, the carbon or nitrogen mineralization potentials of the soils amended with different organic materials were derived on the premise that the rate of C or N mineralization is proportional to the amount of potentially mineralizable substrate as defined by the equation: % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamizaiaado% eacaGGVaGaamizaiaadshacqGH9aqpcqGHsislcaWGlbGaam4qaiaa% bccacaqGVbGaaeOCaiaabccacaqGSbGaae4BaiaabEgacaqGGaGaai% ikaiaaboeacaqGVbGaeyOeI0IaaeiiaiaaboeacaqG0bGaaeykaiaa% bccacaqG9aGaaeiiaiaabYgacaqGVbGaae4zaiaabccacaqGdbGaae% 4BaiaabccacqGHsislcaqGGaGaae4saiaab+cacaqGYaGaaeOlaiaa% bodacaqGWaGaae4maiaabccacaqGOaGaamiDaiaacMcaaaa!5C0E!\[dC/dt = - KC{\text{ or log }}({\text{Co}} - {\text{ Ct) = log Co }} - {\text{ K/2}}{\text{.303 (}}t)\]where Co is the C mineralization potential, Ct is the cumulative amount of CO₂ evolved at time t, and K is the mineralization rate constant. The estimates of C or N mineralization potential, mineralization rate constants and half-time for C or N mineralization are reported for the organic matter amended soils. The relative enrichment of conventional humus fractions after a 30 week period of incubation indicated that the soils could be ranked in the following order of encouraging humification of the organic materials: Haplustults>Haplaquents>Calciorthents.re]19751007