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Topics : Soil Fertility for Forage Crops : Pre-Establishment



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Soil pH and Herbicides

Soil pH also has an impact on herbicide residues which can affect the forage seeding. Low soil pH will cause the triazine herbicides to be bound to the soil. This has several important implications. First, when they are bound this way they are not effective in controlling weeds in the corn. Often this results in higher and higher rates of herbicides being used in an attempt to get adequate weed control. These higher rates mean a greater probability of residual herbicide being in the soil when the forage is seeded. Also, these bound herbicides are released when the soil is limed. If liming is postponed until just before seeding, this release of bound herbicide can have serious detrimental effects on the forage seeding. This effect is aggravated by the use of EPTC (Eptam) when the forage is seeded. The best way to avoid these problems is to maintain the soil pH above 6.2 throughout the crop rotation. This will minimize the adsorption of the herbicide to the soil and result in maximum effectiveness at minimum herbicide rates in the corn. This in turn, will reduce the residual herbicide in the soil and avoid large release of bound herbicide just prior to seeding.