Age-old soil testing coupled with modern technology providing best crop results

[April 07, 2011]  Greg Phillips literally grew up "playing" with dirt. As a youngster he spent many of his out-of-school hours helping his stepdad, Steve Sparks, at Sparks Soil Testing Laboratory. 

Phillips said that when he graduated from high school and headed off for college, he thought that he would never return to soil testing, but as the old saying goes, "Never say never." 

Steve Sparks opened his lab in Lincoln in 1974, offering agricultural soil testing for area farmers and fertilizer dealerships. 

By 1996, GPS was beginning to play into soil testing, and the use of computers was becoming more important in the profession.   

Phillips said these were aspects of technology that his stepdad wasn't comfortable with, so Greg came back to help integrate new technology into the lab. Now, all these years later, he's still here, having taken over in 2004 as the owner of the family business. 

Using GPS in soil testing has fine-tuned the way soil samples are taken and how they are documented for the farmers, but beyond that, the testing business is something that really hasn't changed a great deal over the years. 

What was proven decades ago still holds true today: Soil needs proper pH balances, phosphorus and potash in order to grow good crops, along with nitrogen for corn. 

Soil testing helps farmers see what their soils are lacking and helps them determine how much fertilizer or chemicals that modify acidity need to be applied to a given field in order to produce a high-yielding crop. 

It takes 0.43 pound of phosphate and 0.28 pound of potash to produce one bushel of corn. Knowing this, farmers can examine what is already in the soil at the end of the season and then calculate what is needed for the next growing year.   

For soybeans, the nutrient requirement is 0.85 pound of phosphate and 1.3 pound of potash per bushel produced. 

GPS can also play into saving dollars for the producer. Using satellite imagery, Phillips creates a map of the field and then marks where the soil samples were taken. When test results come back, he sees where soil nutrients are richer or weaker and adjusts fertilizer applications accordingly.

According to studies by the University of Illinois Agronomy Department, GPS mapping can save producers as much as $3 to $5 an acre on fertilizer applications. 

Several years ago there was a push in soil testing to include analysis for micronutrients such as boron, chloride, copper, iron, manganese, molybdenum and zinc. Some of the larger, more commercial labs have incorporated those tests into their standard analysis, but Phillips said that on the whole, it really hasn't panned out. 

In most cases micronutrient deficiencies will show up on plant foliage and can be identified visually. Phillips said that from there, the best practice would be to do a plant tissue analysis. 

Oddly, Phillips said, scientists are seeing a depletion of sulfur in soils. This comes from the fact that environmental standards regulate the amount of sulfur emissions from coal-powered plants. Phillips said that certainly isn't a bad thing, as we don't need the sulfur in the air, and it is better for all of us to add sulfur to the soil when needed than to see it coming "naturally" from acid rain. 

Sulfur is needed by plants in about the same quantities as phosphorus and, depending on the crop, removes between 10 and 80 pounds with each harvest.   

In spite of the known crop needs for sulfur in relatively large amounts, scientists have struggled to get a good handle on this nutrient. Soil and plant analysis procedures are not yet refined to the point where standard recommendations can be made with confidence. 

Looking to the future, Phillips said that what the industry needs and is working toward is a reliable method for testing nitrogen in soils. 

"We're just waiting for a breakthrough from the ag universities. They have been working on trying to do tests on nitrogen, but nitrogen moves up and down in the soil, and with our current technology it is an impossible test."

So what lies ahead? 

Phillips said that Logan County farmers can look forward to working with some of the richest soils in the state for generations to come.

"Logan County soils are some of the best in the state," he said. "Based on the last glacial period, they're very young soils. Maybe a thousand years from now, farmers may have to go to a four-crop rotation like the British did to replenish the soil, but these are very rich soils and they are going to continue to be for a long time."

[By NILA SMITH]

Excerpted from the LDN 2011 Farm Outlook magazine