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Methods Soil moisture sensors and a Hansen meter were put into an alfalfa hay field at two different locations. Six water sensors were planted at three different depths; 1 foot, 2 feet and 3 feet. Soil moisture was monitored for water use. Extension Educator Cindy Kinder and Irrigation Specialist Howard Neibling and landowner Matt McLam periodically met and discussed the soil moisture trends at the three levels.
Chart 1 shows soil moisture at one, two, and three foot levels for site “A”. Site “A” was first irrigated eight days after site “B”. At the first foot level data show typical soil response to irrigation. Soils dried to 100 centibars in some cases and were then replenished. At the two and three foot levels soil moisture did not show individual irrigation response, indicating that added water did not reach these levels before it was used. The two foot level started in May, at 100 centibars and by August, was approximately 20 centibars. The two and three foot sensors indicted crop stress for most of the growing season (approximately July 23rd ).
Chart 2 indicates the soil moisture at one, two, and three foot levels for site “B”. Site “B” was first irrigated eight days prior to site “A”. At the first foot level soil moisture sensors shows typical response to irrigation. The two feet level also showed response to irrigation and the amount of moisture present was always adequate for the whole growing season. This shows that water was being used and replenished at this level. The three feet level also held moisture above 62 centibars for the growing season.
Data logger for up to 6 watermark sensors Reads & records every 8 hours Reads in centibars soil moisture tension (work required to extract water at that moisture content) Cost for meter & 6 sensors is about $550 Hansen Data Logger
Objectives 1. Monitor soil moisture at one foot, two feet, and three feet levels in alfalfa. 2. Understand the relationship between the first foot and the second and third feet during alfalfa crop use. 3. Be able to use the information gathered to determine when to turn the irrigation system on and off at the beginning of the growing season and between cuttings. 4. Determine yield differences between the two irrigation start dates.
Conclusion • Site “B” had good top and subsoil moisture throughout the growing season. • The crop at site “A” was always under some level of water stress. • By irrigating 7 days earlier, site “B” subsurface soil moisture was always adequate to avoid plant stress. • At site “A” the two and three foot soil moisture was always inadequate to supply crop water needs. • At site “A” the water applied could never keep up with the demand.
Situation A major challenge of growing crops in Camas County, Idaho is the high elevation (5100 ft), which shortens the growing season to 60-80 days. Farmers harvest 1-2 cuttings of hay per year, averaging 1-2 ton/acre for dryland hay and 2-3 ton/acre for irrigated hay.
Problem With an increase in electrical prices, farmers with irrigation systems have recognized the need to become more efficient in the management of their systems.
Impact The transfer of new technology and information benefits all producers. This project allowed a Camas County Producer to get hands-on experience in understanding several factors in irrigation water management. These include relationships between irrigation system operation, resulting soil moisture at one, two and three foot levels, crop water use, and availability of moisture throughout the growing season.
Technology Transfer; Monitoring Soil Moisture in Alfalfa, Fairfield, Idaho. Authors: Cindy Kinder, University of Idaho, Camas County Extension Educator Howard Neibling, University of Idaho, Irrigation Specialist, Twin Falls, Idaho.
