published in

The Peace River Farmer and Rancher

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Yellowing of bahiagrass pasture usually observed in the spring and early summer is a common occurrence in Florida. We know that the yellowing is caused by iron deficiency in the bahiagrass leaf due to inadequate iron uptake in the spring. Several years ago we applied iron sulfate in a liquid fertilizer mixture as a foliar application (broadcast spray) to large areas of bahiagrass pasture. The yellowing condition disappeared within a week

Dr. Jack Rechcigl found that bahiagrass yellowing could be eliminated by applying iron chelate to the soil, but the chelate was cost prohibitive. Application of iron sulfate to the soil was ineffective.

Dr. Martin Adjei conducted experiments that evaluated different fertilizer and lime treatments on bahiagrass plots. One very obvious outcome was that bahiagrass forage responded to nitrogen application where lime was applied to increase pH above 5.0. Where lime was not applied and pH was 4.0 to 4.5, the application of nitrogen fertilizer had a negative effect on bahiagrass yield and the yellowing condition was observed. It was best not to apply nitrogen to bahiagrass plots if lime was not applied to increase pH to 5.0 or higher because bahiagrass stand loss occurred.

We experienced a lot of bahiagrass yellowing at the Ona Research Center in the spring and summer over many years. Pastures had not been limed in more than 10 years and soil pH was around 4.5. In January, 2001 we applied 2 tons of dolomite per acre to 300 acres.

In the spring and early summer of 2001 we still observed extensive yellowing of bahiagrass where dolomite was applied. However, in the spring and summer of 2002 no yellowing of bahiagrass was evident. This shows that time is required for the lime source to be dissolved and washed into the bahiagrass root zone, so a quick response should not be expected. In the spring of 2003 we have not seen yellowing in bahiagrass pastures that received dolomite in January, 2001.

It appears that most of the yellowing observed in bahiagrass pastures is a result of low pH which probably prevents bahiagrass roots from absorbing enough iron. This can be corrected with a good liming program. University of Florida/IFAS recommends that the soil pH in bahiagrass pasture should be 5.0 or better. If you are seeing considerable yellowing in bahiagrass pasture, first test the soil pH. If the pH is below 5.0 apply dolomitic of calcitic lime according to University of Florida/IFAS recommendations . This should cure the yellowing problem over time.

For questions or comments regarding this publication contact Findlay Pate

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