A three-year study by Texas AgriLife Research found producers should test soil nitrate levels to a depth of at least 18 inches or more rather than a previously recommended 6 inches.

The new recommendation comes after research re-vealed high levels of nitrogen found in deeper soil depths. Researchers also found cotton is able to utilize these nutrients throughout the growing season. The findings could lead to more than $50 million in savings for Texas farmers and reduce the threat of leaching to groundwater.

"That doesn't include other costs such as extra spraying for insects, defoliation, harvesting and other expenditures associated with rank or excessive growth," said Frank Hons, an AgriLife Re-search scientist who led a study team.

The research, funded by Cotton Inc., took place at the Texas AgriLife Research Farm in the Brazos Bottom region of Burleson County. The fertilizer was applied at various depths down to 42 inches using a hydraulic soil probe in micro plots measuring 4 feet long by about 7 feet wide.

"We would take a core sample every 8 inches of the two rows of the micro plot," Hons said. "We would take a core sample down to the appropriate depth, then take N-15 (nitrogen used frequently in agricultural research) solution liquid and inject at that depth and refill the hole. The N-15 allowed us to distinguish fertilizer uptake as compared to nitrogen al-ready present in the soil."

"We found cotton plants were able to use available nitrogen down to at least 42 inches," Hons said.