Farmer and engineer Clay Mitchell troubleshoots his crop yields the same way an engineer fine-tunes any process: He identifies yield variations and then fixes the cause.

 “The cause can include uneven nozzle and planter flows, poor implement guidance, ammonia/strip-till shank problems and residue distribution,” says the Buckingham, Iowa, farmer, Harvard biomedical engineer and ag technology whiz. “Eliminate as much yield variation as you can.”

Clay and his father Wade, also an engineer, remedied the easy problems a while ago by standardizing practices using RTK guidance, controlled traffic, strip-till and strip intercropping.

Bar coding 1,200 corn plants identified how each plant’s distance from nutrient bands, neighboring plants and residue affect final yield. The bar coded plants were carefully selected from different parts of the field, with each of the hybrids in the field. Below are examples of how scrutinizing farm operations for quality control, or deviation from the average, improved Mitchell Farm’s yields:

Irregular P application: RTK and controlled traffic enable Mitchell to plot plants’ distance from the path of phosphorus (P) and ammonia application. Reviewing soil test results drawn every 16 ft. across 1,000 rows, Mitchell found corn yields vary with swings in P application; from 171 to 252 bu./acre. Although the average yield was a respectable 223.2 bu./acre, the 81-bu. corn yield range reflects unidentified opportunities to standardize yields even further.

The problem was Mitchell’s underperforming dry fertilizer application meters. They created soil P readings ranging from 7 to 47 ppm. He replaced their old black iron dry fertilizer applicator housing with stainless steel housing and Morris spiral fluted rolls to reduce buildup and ease calibration and repairs, and added fertilizer applicator section control. Now, his soil P reading is 6 ppm,and his yield loss due to uneven fertilizer application is zero.

Distance from nutrient band: RTK and controlled traffic systems allow them to precisely band nutrients in the root zone along a 0.5-mile corn row. By barcoding 1,200 plants, Mitchell correlated individual plant growth, development and yield data to nutrient application. Barcodes enable him to track each plant’s growth, photosynthesis, stalk diameter, time of differentiation from its neighbor and yield. The summary data revealed the importance of plant-to-plant spacing and plant-to-nutrient spacing as populations increase.

It also revealed that early-season spindly plants often catch up during pollination and grain fill; not the conventional wisdom, he says. For example, plant #181 (barcode number) began life much smaller than the others. Yet it yielded 242 bu./acre, according to Mitchell’s data. Purdue University also found this: no-till continuous corn plant-height-variability and nutrient availability at the plant level affected yields more than overall delayed growth and development delays, especially at high populations. (See http://bit.ly/PurdueNoTill)

More even residue distribution is a major focus of Mitchell’s quality control efforts. In his high-residue strip-till/no-till, corn, bean and seed corn operation, uneven crop residue affects soil temperature, seed-to-soil contact, nutrient availability (via carbon/nitrogen ratio and soil temps), disease prevalence and seedling emergence. “Uneven early growth generally evened out later in the season as long as we distributed residue evenly,” Mitchell says. His conservation bias favors residue, so he’s bought new equipment to distribute trash more evenly in 2013.

Inconsistent implement guidance skews seedling emergence and growth. These photos, (dog comparisons) taken the same day just 12 rows apart at the same population, show the difference between rows with planter guidance turned on and off. No planter guidance (on the left) resulted in uneven populations of just 18,000/acre. The same planter with guidance turned on (right) had populations of 36,000/acre that had already reached V7-8, versus stages V1-5 on the left. Tractors and implements each have dedicated guidance systems on Mitchell Farm when not experimenting.

“They were planted on the same day, but the taller plants penetrated the residue more quickly. Implement guidance’s evening out of plant spacing in this case has the same effect as more growing degree days,” Mitchell says. “For corn on corn, it is really about getting between the old rows and proximity to fertilizer. We see how vital N sufficiency is in corn on corn, especially as you get crowded. Following beans, rather than bash residue, distribute it and plant more evenly for high-productivity conservation farming.”

Plant survival rates doubled with dedicated planter RTK, and plant height improved by 5-32% (from 2-12 in. to 40 in.) simply by standardizing coulter, fertilizer and planter tracking. Poor guidance results in seeds planted at varying distances from banded fertilizer, and in various amounts of residue, whichaffects seed to soil contact, temperature and disease, causing seeds to rot and not germinate.

Adding dedicated fertilizer applicator steering increased plant height by 200-700% at V7-V8 growth stage. “Having sufficient nutrients at the plant-by-plant level is key to optimizing yields,” Mitchell says.

Long-term correlations between topsoil depth and yield make conservation farming practices top priority at Mitchell Farm. In some cases, Mitchell physically moved accumulated topsoil to low-organic matter patches (see http://bit.ly/168M9dR).

“You leave a lot of yield on the table by not identifying the invisible details that reduce your yields,” Mitchell says. “Anyone can measure this; mark scrawny seedlings with popsicle sticks and then revisit them through the growing season to see whether they catch up. Are there patterns to your markers?”

Strip intercropping (alternating swaths of 12 rows corn/24 rows of beans) captures the economic benefits of continuous corn without its yield hits. For more details on how and why Mitchell uses strip intercropping to reduce yield variations, see the video at http://bit.ly/controlledTrafficMitch and http://bit.ly/intercropMitchell.

Controlled traffic reduces compaction at Mitchell Farm by limiting traffic to 17% of a field. For a video on this, see http://bit.ly/CTMitchell.