Variable rate management backed

A myriad of variable rate management practices and use of a yield monitor have proven to help farming efficacy on Ted Sheely's farm in Stratford, Calif. — site of a recently held Precision Agriculture Field Day.

Sheely, along with a part-time independent farm consultant, Brock Taylor, told interested farmers how the ability to identify various inconsistent characteristics of a crop, such as water stress and insufficient fertilizer, can boost yields and optimize resources that help produce them.

Citing one example, Sheely said when his farm was mapped at the beginning of the current growing season, supervisors deviated from applying the conventional rate of 150 pounds of blanket fertilizer and instead, used a higher amount, though applying it in particular plots.

“By using the variable rate technology, we actually used slightly more fertilizer than we would have used had we gone standard rate,” Sheely said. “But the reason is because of these high yielding areas. It's exciting because it's not just reducing the inputs where you don't need them but now we know from our yield rate monitor data where the four- or five-bale areas are.

“So we are now fertilizing for four or five bales and getting it.”

The goal of a variable-rate input strategy is the creation of accurate application maps that can control a variable-rate applicator. The amount and location of inputs applied to a field are derived from soil test results, yield maps and other management strategies.

Higher yields

Sheely also referred to similar efforts, with the aid of technology, to better address irrigation inconsistency on planted cotton.

“If irrigation is a limiting factor what can we do? We knew there was high water (in some areas) and we had spots on the field that wouldn't grow anything. So we came in and divided a 150-acre field into 50-acre blocks. We sprinkled this with irrigation on some parts accordingly.”

The difference “shocked” him.

“Over the previous three times we picked this with a yield monitor there was this difference, but this year is different,” he acknowledged. “We had a wet year and cool spring, and it was hard getting a stand. That will influence this practice some.

“But if we were to increase the yield in one poor area, to bring it in within a half bale closer to the higher yielding area, we would make a 100 percent return on our investment. I think we are going to easily achieve that.”

Problem solver

Sheely said the farmer should “use the technology you have when you come up on an adversarial condition.”

He said use of a cultivator guidance system at the beginning of the current growing season proved to be especially valuable after rainy weather occurred.

“The rain storm we had was a real frog strangler. You weren't going to get any cotton out of it,” he said. “But since we planted the cotton with a guidance system we knew where the seed was. We hauled a cultivator and set it up 2 inches on each side of the seed. It just fractured the soil and we got perfect stands.”

He said there was an air of confidence when - because of use of the system - after the rain supervisors dug down to make certain the seed was OK.

“We cultivated that whole field without a plant being out of the ground and three days later we had a stand. Had I rotary hoed it, two weeks later I would have been asking, ‘Is it going to make it out?’” he said.

Taylor said relying on data extrapolated from smart sampling (or direct sampling), which involves using spatial information to pick areas within fields where to sample site-specifically, has been beneficial too.

“We did our plant mapping and our tissue sampling in our smart areas or direct areas. That way we are building our database to answer the question, ‘Are we accomplishing what we think we want to accomplish?’ So with direct sampling, the sky is unlimited,” he said, and particularly with regards to permanent crops.

Pistachio sampling

Direct sampling at Sheely Farms' has also been applied toward pistachio crops.

Sheely said he doesn't have a yield monitor for harvesting nuts, but, he was able to use a thermal imagery camera to identify varying irrigation needs.

“… We saw some almonds on a serious slope - one area short of water, one area more than enough,” he said. “So you can pick up issues you otherwise wouldn't know and with almonds at $3 a pound, you can make a small investment and get a very big return.”

Also, all of the farm's pistachio acreage was ranked through smart sampling and with data analyzed from weighing the crops.

“Thus, because we know what the raw weight is coming out of the field, it is giving us a clue of what we can quantify if we are going to invest into something: What is the potential of return?” he said.

Sheely said the outstanding limiting factor in south central California pertains to irrigation. One test project getting started at his farm aims at addressing the issue thanks to a cooperative study with Fresno State University that involves a thermal camera.

Also, in another university cooperative study, with University of California-Davis, research is being conducted on variable rate defoliation.

“It's a Cotton Incorporated state supported project, and a program where we bring some dollars back to the states,” Sheely said. “We know how much defoliation it takes to kill the crop. We do a good job of that. But now we want to know how little can we put on in certain areas and still get defoliation.

“Those are two future areas with potential.”

e-mail: [email protected]

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