Alfalfa needs phosphorous and potassium to thrive and growers should establish benchmarks in fields to determine if there are deficiencies in those nutrients, according to Michelle Leinfelder-Miles, UCCE Delta crops advisor based in San Joaquin County.

She recommends taking 15 to 20 core samples from the top 6 to 8 inches of soil. Sampling at field establishment is usually sufficient to evaluate nutrient needs, she says.

Collect 40 to 60 stems from at least 30 plants for a tissue benchmark. Best time to sample stems is at one-tenth bloom before first cutting.

For alfalfa fertility guidelines, go to http://alfalfa.ucdavis.edu/.

Leinfelder-Miles recommended using granulator 0-45-0, 11-52-0) or liquid (10-34-0) to correct P deficiency. Use muriate of potash (0-0-52) to correct K deficiency, she adds.

Alfalfa weevils

Alfalfa weevils are now producing four generations per season in the San Joaquin Valley and are impacting several cuttings, according to UC IPM specialist Pete Goodell.

There are three different weevil species in California that at one time only impacted early cuttings.

It is mostly the Egyptian Alfalfa Weevil (EAW) that impacts the state’s largest acreage.

Goodell said little weevil research has been conducted of late, and it is needed since the EAW has been more prevalent in heavy populations in several areas of the valley, including Firebaugh and Dos Palos.

Goodell believes the increasing populations are the result of limited biological control and resistance to older pesticides.

Even if control is 80 percent, that means 20 percent remain in the fields. With the higher prices of hay, that represents a significant loss of income, says Goodell, who promised to renew research on the weevil.