FAB N-min Summary and Sampling Notes
Background
We measure nitrogen mineralization to better understand how species diversity and composition will affect nitrogen cycling in the system.
Goal
Briefly summarizes preparation, soil sampling and processing. Please see the following protocols for detailed steps. * Preparation * Coring * Processing Day 1 * Processing Day 2
Schedule
- Day 1: Coring
- Day 2: PVC tubes installment
- Day 3: Processing -> Weighing and shaking
- Day 4: Processing -> Extractions and dry can weighing
Materials Needed
Process preparation
- Urine specimen containers
- Cans
- Sandwich bags
- Printed labels (barcode and non-barcode; contact Dan Bahauddin for barcode labels)
- Scale
- Spatula
- Weigh container
- Deionized water in designated KCl carboy
- Rubber bands
- Autopipetter
Coring
- Metal soil corers
- Labeling tape
- Clean incubation (pvc) tubes
- Red caps
- Labeled sandwich bags
- Plot map with areas designated to take cores
- Coolers
- Ice packs
Processing
Day 1
- Baskets
- Plastic spoons
- Empty tins
- Weighed specimen cups
Day 2
- Plastic pipettes
- Specimen cups with soil and KCl
- Scintillation vials
- Tape
- Disposal containers for liquid and pipettes
- Sharpies
Templates
- Soil weights template for required weights for preparation and processing. Green indicates weights required prior to soil sampling and yellow indicates weights required during processing and blue indicates weights required after processing.
- Soil Labels template]
- Excel Template to send to Dan Bahauddin for Barcode labels
Protocol
3/4 inch PVC tubes 15 cm long with one end cut at an angle are used as the nitrogen mineralization tubes. First soil cores are taken and placed in a plastic sandwich bag, this is the initial sample. Next day, n-min tubes are placed in the ground with red caps on the tops close to where the cores were taken, but not the same exact spot. The soil in these tubes is collected after 30 days, and this is considered the final insitu sample. This is the insitu incubation for N-min. We will also do a controlled incubation. Soil is taken from the initial collection and set aside to incubate at controlled room temperature for 30 days. Please note: Controlled incubation will not always be done during a soil sampling year.
When the soil samples are taken (whether it is the initial sample or the final sample) it is then taken into the lab and two heaping scoopfuls are placed into a pre-prepared, preweighed, barcoded empty specimen cup, one for each plot. These are then weighed and 1M KCl is added to each cup. These are placed on the shaker for 30 minutes. After they are finished shaking, they are placed in the fridge overnight and needs to sit for at least 24 hours. In the morning the contents are pipetted into a plastic scintillation vials. It is important to not get any of the soil into the pipette and into the small plastic vials. These samples were then frozen until they were ready to be analyzed. The soil samples were also measured for soil moisture. They were put into preweighed cans when they were wet, put in an oven overnight to dry and weighed the next day.
Detailed methods
Processing Preparation
To prepare for soil processing all tins are labeled with a barcode and then weighed empty. To make up the 1.0 M KCl solution, add 745.5g of KCl to 10L of deionized water. You will need 50 ml of solution for every sample plus one blank vial for every 25 samples. Add the KCl to the right amount of DI water (accurate to the nearest 10ml) in the appropriate carboy and shake until dissolved. Label specimen cups and fill them with 50 ml of 1.0 M KCl using the autopipetter. Then weigh the filled upsc and place them in the fridge. We use an access database in order to weigh everything. See Dan if there are any questions with the program. Also, label sandwich bags for soil collection with soil labels.
Soil Coring
We took 10 0-15cm cores per plot to use for initial samples. Metal soil corers (approx. 3/4 in. diameter) were used to take the cores. They were marked with labeling tape at 15cm from the tip of the corer. Cores were then taken at different areas in the plot (figure 1) and placed into labeled plastic sandwich bags. Five clean incubation tubes (3/4" dia. PVC, 20 cm long), washed with tap water and a test tube brush, filed to a point on one end and plugged with a red cap on the top end were put in each of the plots (figure 1). These tubes were left in the plots for 30 days; when the soil was collected from these tubes, it is the final insitu sample. The same processing steps are used for the final insitu samples.
Processing
Day 1
The samples were brought in from the field and each plot’s soil sample bag was individually set in a tray along with a plastic spoon, two 50 ml specimen cup, a can, and a ziplock bag. The soil was mixed in the bag and then two slightly heaping spoonfuls were placed in 2 - specimen cups (one barcode label and one non-barcode label for controlled incubation) and 2 large heaping spoonfuls were placed in the can. The specimen cup, can, and soil bag were then grouped together by scanning them into the access program. The controlled specimen cup was weighed and entered into an excel. After being grouped, the cans were weighed and the lids were opened. They were then carefully placed in a drying oven set at approximately 250F. After they dried overnight, the lids were put back on and they were weighed again after cooling. All of the 50 ml specimen cups were also weighed right after being grouped and then placed on a shaker (set at the lowest speed) for 30 minutes. After they were finished shaking, they were placed in the refrigerator overnight.
Day 2
The next morning the 50 ml specimen cups were taken out of the refrigerator very carefully so the soil in the specimen cups would stay settled. Label the scintillation vial with the corresponding plot number. First a small amount of liquid (always be sure you don't get any soil in the pipette) was pipetted (use 1 disposable pipette/sample) into a plastic scintillation vial and the cap was put on. The scintillation vial was shaken and this liquid was thrown out. Then, the scintillation vial was filled 5/6 full with KCl liquid from the 50 ml specimen cup. The plot number was also written with a sharpie on the vial cap. The scintillation vials were organized according to plot number and put into the refrigerator until they were analyzed. The rest of the contents of the 50 ml specimen cup were thrown away.