Over the last month, we’ve been developing a prototype wide bed steam applicator for injecting steam at shallow depths to kill weed seed prior to planting. The device principally comprises a 65 BHP steam generator mounted on a trailer and an elongated bed shaper (Fig. 1). The apparatus applies steam via shank injection and from ports on top of the bed shaper. The goal is to raise soil temperature to >140 °F for > 20 minutes, levels known to kill weed seed (Baker & Roistacher, 1957). Development is still in progress but results of preliminary tests are encouraging as soil surface temperatures were relatively uniform and exceeded 160 °F (Fig. 2). Experiments with baby leaf spinach crops will be conducted in the next couple of weeks. Stay tuned for trial results and reports on weed control efficacy and labor savings. 
References
Baker, K. F., and C. N. Roistacher. 1957. The U.C. system for producing healthy container grown plants. Calif. Agric. Exper. Sta. Ext. Serv. Manual 23.
Acknowledgements
This work funded in part by the Arizona Specialty Crop Block Grant Program. We greatly appreciate their support. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the USDA or the Arizona Department of Agriculture.

Fig. 1. Wide bed steam applicator principally comprising a 65 BHP steam
generator mounted on a trailer and a bed shaper applicator sled.


Fig. 2. Video of wide bed steam applicator. Soil surface temperature is presented
using an infrared thermometer gun.