Jeff Mitchell, cropping system specialist with the University of California at Davis, did a lot of looking over his shoulder at a cotton-tomato no-till field day in Five Points.

But while talking about global competition in precision agriculture and the need to be competitive, he also had one eye on the future and the need to tweak conservation tillage systems he has researched for more than a decade at the University of California Westside Research and Extension Center in Five Points and elsewhere.

“This is about improving the resource base and remaining competitive,” Mitchell said, citing efforts in Brazil, where 65 percent of processing tomatoes are grown with no-till systems, and Turkey, where silage wheat is followed by the no-till planting of transplant tomatoes.

Mitchell concedes it’s been a challenge to show California cotton can benefit from the systems, but he is encouraged by news in a recent Western Farm Press story on cover crops for Arizona cotton production. And he believes systems can be improved as tweaking in California continues with moves to subsurface drip and overhead linear irrigation that could use less water and be more efficient than furrow irrigation.

“Are you likely to be doing the same thing you’re doing today in 20 years?” Mitchell asked growers at the field day.

At the Five Points center, cover crops – including triticale, which is also used in the Arizona systems – are used as mulch. Mitchell said benefits include increasing carbon and organic matter in the top foot of the soil. Advantages of conservation tillage include reducing trips across the field, cutting labor and fuel costs and reducing air pollution.

However, challenges remain, and speakers at the field day enumerated some of them, starting with weed management.

With no-till systems, weed banks in the top 2 inches of soil can increase significantly and the types of weeds can change to more challenging ones, said Anil Shrestha, professor of plant sciences at California State University, Fresno.

With tillage, weed seeds are likely to be buried at greater depths, Shrestha explained.

With no-till, 90 percent of weed seeds are in the top 2 inches of soil. With conventional tillage, 10 percent to 12 percent are in the top 2 inches.

“But by the fifth year, things start to stabilize,” Shrestha said. “Still, there should be zero weed tolerance for no-till systems.”

He said there is likely going to be a species shift for no-till, with nutsedge and bindweed, for example, becoming more common. Over time, there may be more weed densities in standard than no-till systems, he said, but no-till systems with no cover crops had the lowest weed densities, suggesting it’s best to try to get a weed-free cover crop.

Shrestha said that he and other researchers sampled the seed banks in fields at the Five Points station shortly after a heavy rain and found that water infiltration was better in no-till systems “and it was very difficult to sample in no-till without hitting an earthworm. There were none in the conventional plots.”

Costs for weed control in conventional and conservation systems “pencil out about the same – 20 to 30 percent of production costs,” said Kurt Hembree, UCCE weed management farm in Fresno County.