Effects of lime rate on corn root characteristics under enhanced ammonium supply
1991
Ogango, K.O. | Teyker, R.H.
Plant growth under enhanced ammonium supply (EAS) can benefit from control of root-media acidification. Corn (B37XB79) was grown in a greenhouse in 18.9-L pots containing Bloomfield fine sand (coarse-loamy, mixed, mesic, Psammentic Hapludalf) with an initial pH of 5.4. Soil pH was adjusted using either CaCO3 or Ca(OH)2 to provide pH increments up to pH 7.4. Nitrogen (100 mg/kg) was added as (NH4)2SO4. A nitrification inhibitor was added to minimize oxidation of the NH4. Dry weights and Kjeldahl N were determined on leaves, stalks, tillers, and roots of 38 d plants. Acidity was measured from rhizosphere (pHr) and bulk (pHb) soil samples. Roots were sub-sampled for length and tissue NH4 determinations. Corn growth at 38 d was not significantly affected by lime amendments. Liming with either form promoted a longer, finer root system. Root tissue NH4 concentration decreased as rhizosphere pH increased for both lime forms up to a rhizosphere pH of 6.9. Rhizosphere acidification, the difference between pHr and pHb, decreased with lime rate, especially for the CaCO3 form. Effects on root parameters were generally associated with pH differences and not with lime form.
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