California State University, Fresno’s Center for Irrigation Technology (CIT) is researching alternatives to help cotton farmers on the San Joaquin Valley’s West Side find other higher-value crops to revitalize returns.

Alternative crops such as tomatoes or melons are not nearly as comfortable as cotton in West Side soils due to the buildup of salt, selenium, boron and other chemicals that has made the soil nearly inhospitable to salt-sensitive field and row crops.

To help reclaim some of the acreage for vegetable crops, a CIT research team is exploring new methods for changing the chemical properties of the soil through subsurface drip irrigation.

“Transitioning from cotton to vegetable production and from flood to drip irrigation presents some new challenges,” said CIT soil scientist Dr. Florence Cassel Sharmasakar, who is leading the research effort with Dr. David Gooraho, an assistant plant science professor.

“Vegetable crops are more sensitive to salinity and more susceptible to disease and deficiency when grown under saline-sodic soil conditions.”

Processing tomatoes are affected by soil salinity and calcium deficiency, she noted.

According to Cassel Sharma, reclamation of saline-sodic soils has traditionally involved application of soil amendments high in calcium to increase available calcium to plants, or applying greater amounts of water in order to leach the salts down below the root zone. This has been done through surface systems such as flood and furrow irrigation. With increasing restrictions on water use on the West Side, however, growers are being forced to try new methods which have the potential for greater water-use efficiency.

“The challenge is how to address the reclamation of saline-sodic soils in the root zone by utilizing subsurface drip tape as the avenue for application,” Goorahoo said.

Little research has been conducted on soil amendments through subsurface drip systems, the researchers noted, but potential benefits are significant, even more so with added potential of water savings.

The research team is examining two specific reclamation alternatives that could create an improved environment around the drip tape:

  • One is the application of calcium fertilizer through the drip tubing (fertigation).
  • The second is adjusting the pH of the water with acid (acidification).

Both treatments attempt to alter soil chemical properties to make the proper nutrients more available to the crops.

This research will provide important information on the effects — positive or negative — of each reclamation method on tomato yield, blossom-end rot, soil calcium availability, plant calcium uptake, and infiltration rate. The researchers hope to increase processing tomato yields significantly with effective soil amendment, Cassel Sharma said.

The project is in its first season this summer, with results are expected next year. For details, contact Cassel Sharma at fcasselss@csufresno.edu or Goorahoo at dgooraho@csufresno.edu.

(Copy by Steve Olson, publications editor of the California Agricultural Technology Institute at Fresno State.)