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Managing soil pH in the herbicide strip

herbbandfertapplication

Its leaf sampling time (see here for previous post on leaf sampling procedures) and based on the calls I’ve gotten many growers are wisely taking this opportunity to pull soil samples as well. Many have found that pH in the herbicide strip is lower than that found in the middles. When we were doing the work on fertilizer placement and comparing broadcast band applications of dry N fertilizers with broadcasting over the whole orchard area, herbicide sprayer application of N, and injecting N through the irrigation system, we observed that soil pH is always lower in the herbicide strip regardless of the fertilization method you use (see here for full research article). You do have the potential to drop the pH faster in some situations where you concentrate fertilizer N in the strip, but its always lower in the strip. This is because the vegetation growing in the middles keeps the organic matter levels up, which helps to buffer soil pH, allowing it to remain a little more stable than that observed in areas free of vegetation.

Managing soil chemistry in the herbicide strip is vitally important because that is where the tree’s feeder roots are located around irrigation emitters. After their transformation to nitrate-N,both ammonium and urea fertilizers have an acidifying effect on the soil to which they area applied. In order to manage this, growers should take their soil samples within the herbicide strip (where it is most likely to drop first and to the greatest degree) and lime based on this reading, focusing the lime application toward the herbicide strip. As mentioned earlier the vegetation in the middles helps to buffer the pH so you probably won’t need as much lime in those locations. It would be wise to check pH in the middles every few years and make an additional lime application to the middles when pH drops below 6.0.

 

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About Lenny Wells

I am a Professor of Horticulture and Extension Horticulture Specialist for pecans at the University of Georgia. My research and extension programs focus on practical cultural management strategies that help to enhance the economic and environmental sustainability of pecan production in Georgia.