I have had the pleasure to conduct a variety of experiments, watch numerous management talks and take many classes on the scientific method. During these adventures I've noticed that people seem to misunderstand (or not comprehend the full power of) replication.
Replication is the repetition or duplication of an experiment. On the surface this seems pretty straightforward; why would someone want to replicate or duplicate an experiment? They do it to double-check that the results are correct.
If I want to test to see if hummingbirds prefer red or yellow feeders, I can put out two colored feeders and count the number of visits. Great! Right? Not exactly.
The experiment is not replicated. What if one feeder is closer to something the hummingbirds do not like? They would avoid that feeder and prefer the other no matter what the color. Replication solves this problem.
Professionals get it wrong sometimes too. I just visited a colleague who has a growing facility with 3 replicate greenhouses (3 repeated greenhouses in a row). One of the researchers using his facility had all the trials in one greenhouse. It was the south-facing greenhouse. What if the south-facing greenhouse was slightly warmer than the average greenhouse? They will not know if this influenced the result.
How many weed trails have we seen that have been conducted at a site, spray herbicide A here, herbicide B there. Done. Great! Right? Not exactly. It certainly helps to have the initial trial, and its even more helpful to replicate the experiment.
Replications can occur across space or time (this sounds like Star Wars), and on the ground it means experiments can be repeated over a variety of distances, or over different seasons.
Replications Across Space
Conducting an experiment is good; conducting the same experiment (especially when it comes to weed management) in multiple field sites, counties or states is even better. There are more herbicide resistant weeds in the Central Valley than outside that area. Same species, different resistance. How do we know? Replicated experiments across the state.
Replication Across Time
Weed scientists like to conduct herbicide trials, and I do them myself, and how many of them are conducted every year for 5 years at the same site? This type of replication allows one to determine if the result is the same during different years or seasons. Some populations of hairy fleabane (Conyza bonariensis) are resistant to the herbicide glyphosate during the summer, (they will not die when sprayed) but when those same resistant plants are sprayed during the winter they are susceptible (see footnote*). This is fascinating! Spray in summer and it grows like a weed, spray in winter and growth is reduced. The only way this was discovered was by replicating experiments across time; applications were made in spring, summer, fall and winter. On a side note the researchers in charge of this project thought they mixed the resistant with susceptible seeds and repeated (i.e. replicated) the experiment several times until they understood the results!
Replication Across Space and Time
It's the gold standard; the researcher conducts an experiment at multiple sites and repeats it over different durations. It also takes a lot of work. One simple experiment now has multiple sub-experiments. But you know how well it really works.
Just because we see weed trials doesn't mean it has been fully vetted. Simple trials are good, they teach us a lot. Multiple trials are better. Control plot, treated plot, good. Control plot, treated plot, repeat, repeat, repeat here, repeat there, repeat next year, and repeat in the winter, ...even better.
*Note: I am not advocating spraying resistant hairy fleabane with glyphosate, you should consider an IVM (or IPM) program to tackle this problem.
With the drought our perpetual salt problems are exacerbated due to less water and often more saline water. The question keeps coming up if gypsum (calcium sulfate) can help correct the problem. And the answer is maybe, but along the coast, probably not. The problem there is confusion about what is a saline soil and what is a sodic soil. A saline soil is one that is dominated by salts, but has a pH below 8.5 and can have a white crust that will actually taste salty. A sodic soil is one dominated by sodium, has a pH above 8.5 and can be saline, as well. Often though, there is a brownish cast to the surface salt crust. This is caused by dispersion (dissolved) of soil organic matter caused by the high pH. It's like cooking with vinegar when you make ceviche out of fish. Saline soils often have a high calcium content and may have sodium, but at a very low ratio compared to calcium. Most of the sodic soils in California are found in the Central and Imperial Valleys. Along the coast, the soils, if they have a problem, are largely saline.
The way gypsum works, is that the added calcium displaces soil sodium, pushing it lower in the soil column. The process also requires a lot of water to move the sodium through the soil column.
So the answer is, along the coast, gypsum is unlikely to improve soil conditions. However, there are other instances where it might help. In the San Luis Obispo area there are lots of serpentine derived soils that have a high magnesium content relative to calcium. And they commonly aren't saline, just an imbalance between the two cations. This can lead to infiltration problems and calcium deficiency in plants. Apples are especially sensitive to this high Mg:Ca ratio and develop a condition called “bitter pit”, a surface, brown pitting in the skin. There are other crops, like celery that are especially sensitive, but even avocado can be mildly affected. In the case of magnesium imbalance, gypsum can help.
Thank you to all of you (participants numbered in the hundreds) who completed the survey, online or at extension meetings, done over the past few months concerning what resources you refer to for production information.
Nice to see that UCCE and UC are still valued a lot by growers and agricultural professionals. We'll try and keep it that way!
Thanks to Margaret Lloyd and McNeil Roberts of UCD for putting this together and sharing the information. Really appreciate working with you both.
UCCE and UC researchers are the number 1 resource for production knowledge.
"I'm a very proud 4-H member, from 4th grade to early college, in beef, rocketry and sugar beet (projects)," Jacobsen said. "When we think of 4-H, it's just so much more than those projects. There are so many leadership opportunities for these kids."
Jacobsen interviewed John Borba, the 4-H youth development advisor for UCCE in Kern county.
"4-H has an emphasis on citizenship, leadership and learning life skills," Borba said. "We encourage youth to take on leadership responsibilities, where the older youth mentor the younger youth."
Borba said 4-H program in California, which has 120,000 youth participants and 14,000 adult volunteers, isn't just for rural kids.
"In the San Joaquin Valley, 4-H is offered in the traditional mode, 4-H clubs, where volunteer leaders assist the youth in different programs. But we also have programs on military bases, active duty and national guard, and we have after-school programs where we teach the staff ... to provide 4-H programs after school."
Jacobsen interviewed Shanon Mueller, the director of UCCE in Fresno County, at the Garden of the Sun, a one-acre demonstration garden created and maintained by the UCCE Master Gardener program.
She explained the role of UCCE's farm advisors and nutrition educators.
"Farm advisors bring the research-based information to the county," Mueller said. "A lot of times we can't directly import that. We will adapt that research so it's locally relevant. We do research trials, demonstration trials. We have field days, workshops, meetings."
Mueller continued, "Our goal is to bring the most up-to-date information to growers on varieties, production practices, irrigation, pest management. Any component that relates to agriculture to make sure we keep our ag economy strong."
Mueller said Fresno County UCCE maintains one of the premiere nutrition programs in the state. Much of the nutrition education takes place in Fresno County schools.
"They talk about good nutrition, physical activity and health issues in classrooms," Mueller said. "One of the fun activities they do is monthly tasting time. They will bring some product for the kids to taste in a comfortable environment. All the kids are tasting jicama, apricots or something they haven't tried before in hopes that they'll try it and like it and that their parents will buy it at the grocery store."
Valley's Gold is produced by the Fresno County Farm Bureau and appears on the local PBS affiliate, KVPT.
The ag education episode can also be viewed below. Borba's interview begins at 12:25 and Mueller's at 15:08.
Brian Marsh, the director of UC Cooperative Extension in Kern County, talked about the upcoming UCCE centennial celebration with host Scott Cox on First Look, a web video and radio program that provides Kern County resident with an overview of the day's news. The program is broadcast on the Bakersfield Californian webpage and on KERN radio.
At a dinner Aug. 21 marking the 100th anniversary of UC Cooperative Extension, the organization will honor 14 Kern County families with a farming legacy that stretches back 100 years or more. Cox was impressed.
"For a family farm to be in business for 100 years, it's a tough way to make a living," Cox said. "There's a lot of temptation for kids to go off to school and learn how to do something else and sell the farm off. These are people who have stuck it out."
Marsh said the farming underway today is different than 100 years ago.
"The children are coming back to the farm with advanced degrees," Marsh said. "Farming isn't the simple life. .. There is a lot of technology, there's a lot of regulations to deal with. A lot of our products are exported, so you're dealing with international trade and residue concentrations in other countries."
Cox agreed. "From agribusiness, to science, there's a lot going on out there."
Marsh emphasized the importance of the California farming industry. "I like to eat everyday," he said.