Field Notes

Twitchell Alfalfa: 2014-10-30 12:50:00 (DOY 303)
Author: Joe Verfaillie
Others: Patty

Summary: Standard data collection, field has been mowed and baled, install three FR CO2 probes, trouble with power relay.

Alfalfa
2014-10-30

I arrived about 12:50 with Patty. It was mild with a high thin overcast and a light breeze but looks like weather coming from the west. The field has been cut and baled, probably shortly after our last visit. The road and ditch were dry.

Patty cut the alfalfa around the radiation and soil sensors.

The 7500 read: 287ppm CO2 and 781mmol/m3 H2O, 53SS, 24.48C, 101.1kPa
There were a bunch of spider webs hanging off the eddy sensors. After cleaning the 7500 read: 410ppm CO2, 549mmol/m3 H2O, 81.4SS

Patty did spectral measurements and soil respiration:
1 = 3.0, 2 = 3.7, 3 = 4.8, 4 = 5.5, 5 = 5.7, 6 = 5.5

I added three Forerunner probes to the soil respiration system. A problem with the power relay put the CR10x into a reboot cycle. I think the transistor died, although there might have been a power loop. I cut the transistor out of the circuit and drove the relay directly from the switched 12V port on the 10X. The Forrunner probes have a 0-5V output and need voltage dividers to be used with the 10X. I didnâ€™t appreciate this until too late and made a forest of resistors to connect the probes to the AM416. I need to replace the mess next time. Also I was not sure of the wire colors for the new GP probes â€“ I used gray CO2 and blue Temp.

Probe 1, sn GP2013ex02, 3%, -16cm
Probe 2, sn GP2013ex03, 3%, -8cm
Probe 3, sn GP20140009, 2%, -2cm

Patty buried the probes near between the radiation post and the soil co2 box.

2 photos found

TA_autocam_20141030_1215.jpg ( 2014-10-30 12:15:02 ) Full size: 1920x1440
Patty and Joe install Forerunner probes