LFL: Nitrogen Mineralization Lab Incubation
Soil cores are taken at 10 areas per plot at a depth of 10 cm usually after tillage. One step forward is taken in the row and the core is sampled from the resulting footprint. Five soil cores (1.9 cm diameter cylinder wet tip hand probe) are taken in a zigzag pattern up between rows 2 & 3 and five soil cores are taken in a zigzag pattern down between rows 4 & 5 using the footprint method. The cores are taken on either side of the row. The cores are placed directly into a plastic zip lock bag and placed on ice in a cooler.
The soils are immediately taken to the laboratory and placed in a cooler at 4 ° C until analysis can be performed.
The composite soil samples are mixed, sieved through a 6 mm sieve and sub-sampled for moisture determination. For each composite soil four 20 g dry weight equivalent aliquots are weighed into 100 ml plastic specimen cups and brought to 50% water holding capacity.
One cup/soil is immediately extracted (0 day) with 100 ml of 1N KCL and inorganic N (N-NO3- and N-NH4+) concentrations are analyzed using a Lachat automated colorimetric analyzer.
The other three cups are placed in plastic storage containers (containing a thin layer of water on the bottom to maintain humidity), loosely capped and incubated in a darkened controlled temperature room at 25 ° C. At each interval (30, 70,150 day) one cup/soil is removed and extracted with 100 ml of 1N KCL. Inorganic N (N-NO3- and N-NH4+) concentrations are analyzed using a Lachat automated colorimetric analyzer. (See Soil Nitrates for more information on extraction procedure).