Field Notes

2013-06-05 11:30:00-->
Other sites visited today: Twitchell Rice | West Pond | Sherman Island | Mayberry | DWR Corn

Twitchell Alfalfa: 2013-05-24 09:30:00 (DOY 144)
Author: Cove Sturtevant
Others: Joe, Dennis, Laurie

Summary: Initial setup of tower, CO2 flux, camera, ground sensors, separate radiation stand in field.

Twitchell Alfalfa
2013-05-24

We arrived about 9:30 PDT. Joe, Dennis, Laurie and I set up the new tower at the alfalfa site. The site is pretty homogeneous. The alfalfa was about 20 cm high and beginning to flower. I think the field was recently mowed and baled shortly after May 2nd. It was warm and breezy.

We placed the tower scaffold (just railings directly on adjustable feet) on the west side of ditch bisecting the field. The Sonic and IRGA went on the northwest corner of the scaffolding. A Canon auto camera was mounted on a 4x4 treated post in the southwest corner of the scaffolding. Two Theta probes (at 5-10cm and 20-25cm), three Hukseflux SHF plates and three soil temperature profiles (type T thermocouples at -2, -4, -8, -16 and -32cm) were installed in the field. The cables for all ground sensors are buried a few centimeters underground to avoid damage when the field is mown. A single 140W Kyocera solar panel was bolted to the southeast corner of the scaffolding with security bolts. A heavy chain was also attached to the center spar of the panel and a stake buried in the ground with security bolts. The buried stake needs to be replaced with screw-in anchor.

Tower height: 2.8 m from field level to middle of sonic path
Sonic N mark aligned with true north
The IRGA is 30cm east of the sonic.

The radiation measurements (Hukseflux NR01, two K&Z PAR (in/out) and an LED sensor) are logged on a separate data logger (CR10x with AM16/32) about 20 m into the field interior. The radiation stand has its own solar panel, charge controller, and battery. The bottom of the lower shield on the NR01 is 158cm above the ground.

The tower was collecting data when we left, all readings good. We had to borrow an Ethernet cable from West Pond to connect to the 7550. We need to bring another Ethernet cable next time. We also forgot to bring a 7500 mount so MacGyver (Joe) made one from scratch (Fig. 1). Its probably as good as an original but we may consider bringing a bona-fide replacement next time.