Varying Soil Conditions Can Impact Nutrient Levels

November 19, 2002

WOOSTER, Ohio - This growing season's topsy-turvy weather may have impacted more than crop performance and subsequent yields.

Maurice Watson, an Ohio State University Extension soil specialist with the Ohio Agricultural Research and Development Center (OARDC), said that the wet spring followed by a summer drought may have also affected soil nutrient concentrations.

As a result, growers should test their soil for nutrient availability following harvest to determine whether or not fertilizer is required before spring planting.

"Most growers test their fields to determine nutrient concentrations. We recommend testing every three years, so that growers over time get a feel for the natural variation of nutrient levels in the soil," said Watson. "This year is just more of a concern because of the extreme wet and dry conditions we encountered."

Watson said that varying soil conditions affect a plant's ability to uptake nutrients effectively. Under extreme wet conditions, the oxygen supply to the roots is limited, affecting the uptake of nutrients, even though the nutrients are present in sufficient concentrations. Under drought conditions, plants are unable to take up nutrients because of the lack of water flow to the roots and the lack of growth or slow growth of the plant.

"Because of this year's drought, it is possible not as much fertilizer will be needed by next year's crop on a field that was sufficiently fertilized this year. In addition, it is possible that not enough fertilizer was applied this year because of the very wet spring," Watson said. "Despite either condition, a soil test will determine whether or not nutrients are at their optimum levels."

Watson said growers should mainly test for phosphorus and potassium, the two main elements that can impact a plant's performance if they are in deficient levels.

"In a nutrient-deficient situation, the biochemical reactions are not going to be what they should be under normal conditions. You may get a reduction in protein formation, which is the main building blocks of the plant," said Watson. "A plant will tend to take some nutrient elements from the older leaf tissue and put it toward the younger leaves to compensate, particularly in the case of nitrogen or potassium deficiencies. As a result, you don't get the normal development of the plant and yield is then reduced."

Plants may also run into a nutrient imbalance if nutrient levels are too high in the soil.

Nutrient levels are also impacted by soil type (sandy soils have less of a reservoir for nutrients than clay or silt loam soils), as well as the type of crop being planted. For example, corn silage and alfalfa remove more potassium from the soil than grain crops.

Guidelines for choosing a quality soil-testing laboratory can be found online at http://ohioline.osu.edu/hyg-fact/1000/1133.html. More information on fertilizer and lime recommendations for corn, soybeans, wheat and alfalfa is available in the Tri-State Bulletin E-2567, which can be obtained from local county Extension offices or online at http://ohioline.osu.edu/e2567/.

Author(s): 
Candace Pollock
Source(s): 
Maurice Watson