Across the Midwest and Midsouth, limestone may be the “Rodney Dangerfield” of plant nutrients: It doesn't get adequate respect.
Most farmers agree that liming low-pH soils will pay. But landlords and renters sometimes disagree about who should pay for it.
“Liming low-pH soils can repay costs the first year,” says Gene Stevens, crops production specialist at the University of Missouri (UMC) Delta Research Center. “And the benefits of liming last for at least three years.”
For the past two seasons, Stevens and David Dunn, UMC soil test lab manager, tested the short-term effects of applying lime to cotton ground.
Cotton is a nitrogen-hungry crop. It takes about 3 lbs of limestone to neutralize the acidity generated by applying 1 lb of nitrogen as ammonium or urea. Stevens and Dunn applied two different lime sources (calcite or “white” lime and dolomite or “red” lime) and compared the resulting yields with untreated checks.
“Initially, the soil was fairly acid, testing 4.6 pH,” Stevens points out. “We applied 2 tons/acre of each different form of limestone.”
Here are the results, in pounds of cotton lint yield per acre:
| Treatment | Average Yield |
|---|---|
| Untreated | 649 lbs/acre |
| Calcite | 735 lbs/acre |
| Dolomite | 769 lbs/acre |
“The average yield increase from liming ranged from 86 to 120 lbs/acre,” says Stevens. “Using the cotton market loan price of 52¢/lb, the gross increase per acre was $45-62 in the first year.”
The cost of buying, hauling and spreading the limestone averaged $20/acre. The researchers applied 2 tons/acre for a total liming cost of $40/acre. At that cost, the first-year value of liming ranged from $5-22/acre over the income from untreated check plots.
“During the economic crunch of the 1980s, many producers cut back on liming rates,” recalls Stevens. “Unfortunately, lime applications on all farms have not returned to amounts used before the farm crisis. But without adequate lime, growers can be wasting a lot of fertilizer dollars.”
He adds, “We studied the first-year value of liming on low pH cotton ground, but I think the benefits would hold for most crops. And you don't have to wait to recover your costs.”