LFL: Soil Carbon and Nitrogen

Sampling

Sampling is conducted by one of two methods

Method 1

Soil cores are taken at 5 areas per plot at a depth of 25 cm. Three soil cores (1.9 cm diameter cylinder wet tip hand probe) are taken in a zigzag pattern up between rows 2 & 3 and two soil cores are taken in a zigzag pattern between down rows 4 & 5. The cores are taken on either side of the row. The cores are combined in a pail, hand crumbled, hand mixed and put into a cardboard soil box. Any remaining soil is placed backed into the plot. The boxes are then placed (within 2-3 hrs of sampling) into the soils dryer (low temperature convection oven) at 110-140 ° F until dry (at least 48 hrs). After removal from the dryer, the soils are then ground using a Hammermill Grinder through a 2 mm sieve and placed back into the box. The soils are then taken to the laboratory for analysis. (See Deep Core Nitrates for sampling protocol for sampling of deep cores).

Method 2

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.

Laboratory analysis

Analysis corresponds to choice of method.

Method 1

Sub-samples are placed in a Qorpak jar containing several metal rods, capped, and placed on a rotary grinder overnight. The ground soil is then placed in plastic vials for future analysis/storage.

Method 2

The composite soil samples are mixed and sieved through a 6 mm sieve. Sub-samples are removed and allowed to air dry. These samples are ground with a mortar and pestle and placed in plastic vials for future analysis/storage. If mortar and pestle is insufficient, the soil is placed in a Qorpak jar containing several metal rods, capped, and placed on a rotary grinder overnight. The ground soil is then placed in plastic vials for future analysis/storage.

The dried, ground soils are weighed on a microbalance into tin capsules for analysis on a Carlo Erba CHN analyzer for % Total Carbon and Nitrogen.