• Nitrogen management in citrus under low volume irrigation, a topic certain to attract more interest because of environmental concerns about nitrates from crop land.

Mary Lu Arpaia, with the UC Kearney Research and Extension Center, talked of a study of leaching losses of nitrogen and the impact on fruit quality in relation to total applied nitrogen.

Foliar application of nitrogen resulted in lower groundwater levels of nitrates than soil application. Maximum yield and lower soil nitrate can be achieved using a combination of foliar and soil applied nitrogen, Arpaia said.

Maximum yield was attained with one to 1.5 pounds of nitrogen per year per tree. Peel thickness increases and peel firmness decreases with increased application of nitrogen.

• Partial root zone drying compared with conventional irrigation in citrus.

Carol Lovatt, professor of plant physiology and plant physiologist at UC Riverside, talked of research on cutbacks in irrigation and impacts on the bottom line – and fruit size – for growers.

She explained that partial root zone drying meant using two irrigation lines on opposite sides of a tree, alternating periods of irrigation so that one side was wet, the other dry.

That approach had been touted Australia years ago, but Lovatt and other researchers found that cutting irrigation in that way – and reducing conventional irrigation – by as little as 20 percent cut yield in citrus and resulted in smaller fruit.

“The real hit was on fruit size,” she said.