Though their numbers may be dwindling, a handful of San Joaquin Valley cotton growers still committed to the crop learned the latest strategies for continuing to produce the fiber crop profitably at a recent University of California Cooperative Extension field day at the West Side Research and Extension Center, Five Points, Calif.

“You really are dealing with a situation here that is unlike anywhere else in the country,” said Ed Barnes, director of agricultural research for Cotton Incorporated. “I know you guys who have survived up to this point are the cream of the crop.”

Field day topics addressed the challenging realities of growing cotton in California today, with information on precision agriculture, variety selection, crop rotations, irrigation and pest management, and overall strategies for reducing input costs and cotton more efficiently and more profitably in the Central Valley.

UC IPM Farm Advisor Pete Goodell detailed how changing crop patterns are impacting traditional integrated pest management in Valley cotton.

“One of the things we are now really looking at is whether the IPM system we have developed in cotton is dependent on or independent of the changing landscape in the San Joaquin Valley,” Goodell said.

Lygus in particular were challenging for West Side cotton growers this summer as increased safflower acreage in neighboring fields dramatically increased lygus pest pressures in cotton.

Growers in recent years have been able to manage their cotton crop with two to three insecticide applications a year, thanks in large part to the IPM program developed when cotton dominated the Valley. But with new crops providing additional hosts for lygus and other pests, that is changing.

Today cotton is almost a footnote to other field, row and permanent crops and growers as a result need to manage pests — specifically lygus — from “outside the field,” Goodell said.

“The community has to manage the IPM landscape. This is a community problem and it’s going to require a community solution.”

The UC is currently participating in a four-year, multi-state project looking at the movement of lygus in the ecosystem in the Western U.S.

Goodell said researchers hope to learn the impact of host crops such as seed alfalfa and safflower on the migration and population density of lygus in secondary crops including cotton. The role of other neighboring crops, such as almonds, that might act as a shelter for lygus as they migrate into cotton from nearby host crops, is also being looked at.

UC Extension Specialist Jeff Mitchell shared recent work on using conservation tillage with and without planted cover crops of triticale, vetch and rye to reduce tillage in cotton and tomato crop rotations.

In his most recent trial, canning tomatoes are transplanted into non-tilled cotton fields that have been shredded but otherwise not cultivated. Mitchell said growers are learning better how to establish cotton crops in no-till environments and plant back into existing tomato beds.

The key to success, he said, is to plant into adequate moisture and use starter fertilizer to help establish the crop.

Researchers at the station are also conducting trials on various irrigation strategies to assess and establish guidelines for irrigating Pima and Acala cotton under new water realities, said Fresno County UC Cooperative Extension Farm Advisor Dan Munk. Now in its third year, the irrigation study is looking at the difference in yield and water use between drip irrigation, deficit irrigation and full irrigation on a number of determinant and indeterminant varieties.

Similarly, UC Statewide Cotton Specialist Bob Hutmacher said the UC is re-examining nitrogen recommendations for cotton given rising fertilizer costs and diminishing returns for cotton.

Based on new scenarios for growing cotton, Hutmacher said growers might be able to reduce nitrogen applications from previously recommended levels. Previous studies on nitrogen management focused exclusively on Acala varieties in the San Joaquin Valley and also did not account for newer rotational crop patterns.

“Under quite a few different rotations, such as lettuce or others, there may be opportunities to back down on N applications without impacting cotton yields,” Hutmacher said.

He recommended growers base their N applications on preplant soil nitrate nitrogen (NO3-N) levels. If the top 2 feet of the soil profile has less than 55 pounds residual nitrate-nitrogen, Hutmacher suggested growers apply 150 to 175 pounds preplant N. For levels between 55 and 100 pounds residual nitrate N, apply 100 to 125 pounds per acre, and for residual levels above 100 pounds, limit preplant nitrate-N applications to less than 75 pounds per acre.

In any case, Hutmacher said, UC trials do not show favorable yield responses with higher N applications above 200 pounds per acre and in some cases high nitrogen applications can actually hurt yields.

Hutmacher noted it is important growers consider yield potential, variety and other variables to determine whether they should fertilizer at the high or low end of the range, and also implement split applications or other methods to minimize N losses through leaching or runoff.