C:N ratio - Colorado State University€¦ · C: N ratio • Total N includes organic N, ammonium N...
Transcript of C:N ratio - Colorado State University€¦ · C: N ratio • Total N includes organic N, ammonium N...
C:N ratio
Common C:N ratios
%C %NBlood meal 43 13Legume Hay (dry) 40 2-2.5Fresh cow manure 12-20 0.6-1.0Oat straw 48 0.5Wood chips 25-50 0.1
C: N ratio
• Total N includes organic N, ammonium NAnd nitrate N.
C:N ratio can be estimated by multiplyingthe percent carbon of each ingredient by the number of parts by weight of that ingredient and then adding the carbon totals for ingredients.
Measuring C:N
• Nitrogen is measured byKjeldahl method (TKN)Combustion method
Measuring C:N
• The TKN method will analyze for organic N and ammonium N, but not nitrate N
• Nitrate can be recovered by modifying the TKN method
Measuring C:N
• Combustion method uses a combustion furnace such as the Leco 1000 CHN analyzer
C:N parameters
• The dividing line between immobilization and release of N is about 20:1
• >30:1 results in immobilization during the initial composting process
• 20-30:1, neither immobilization or release of mineral N
• <20:1, release of mineral N early in the decomposition process
Composting effects on C:N ratio
• Composting causes organisms to form new cell material using their stored N
• In the process carbon is burned• Organisms get rid of excess N as ammonia
C:N
• Since microbes use about 30 parts C for each part N an initial C:N ratio of 30 promotes rapid composting and would provide some N in an immediately available form in the finished compost
• Where C:N >30, there is loss of N through immobilization
Research
• UC studies show that C:N ratios of 30-35 were optimum
• Composting time increased with higher C:N ratios• If unavailable C is small, the C:N ratio can be
reduced by bacteria to 10• Composting material with a higher C:N ratio
would not be harmful to the soil,because the remaining carbon is so slowly available, N immobilization would be minimal