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Lime Induced Plant Growth Depression in an Alluvial Entisol from Costa Rica¹

ABSTRACT

Poor plant growth in field experiments following clearing of a forested virgin Entisol in eastern Costa Rica and the subsequent detrimental effect of lime on growth of warm-season grasses were studied in greenhouse and laboratory experiments. Greenhouse experiments were carried out with pangolagrass (Digitaria decumbens Stent) by sterilizing a virgin surface soil, limed with 0, 4, and 8 meq/100 g of CaCO₃, with heat and gamma radiation. Incubation experiments in the laboratory were conducted with a differentially limed surface soil that had been in pasture for 8 years and its subsoil. Every 2 weeks, for 10 weeks, samples from the incubating soils were extracted with water. Calcium, Mg, K, Na, NO₃, SO₄, P, and Cl were determined in the water extracts. Electrical conductivity in the soil was measured before and after water extractions. After 10 weeks of incubation, electrical conductivity was measured in saturated soil extracts. Soil organic matter was determined before and after incubation.

The negative effect of lime persisted in the sterilized soils; however, water leaching of unlimed and limed virgin soils markedly improved pangolagrass growth. Laboratory studies showed considerable increases in water-extractable Ca, NO₃, and SO₄ ions with increasing lime rates and incubation time in the pasture surface soil and its subsoil. Electrolytes reached a maximum at 2 weeks of incubation. Conductivity measurements higher than 4 mmhos/cm in saturated soil extracts after 10 weeks of incubation indicated harmful concentrations of electrolytes which were apparently derived from lime and biological decomposition of soil organic matter.

¹ Florida Agr. Exp. Sta. Journal Series no. 5045.

² Graduate Student, Soil Science Dep., Univ. of Florida, Graduate Student, Soil Science Dep., Univ. of Florida (presently graduate student, Agronomy Dep., Iowa State Univ.), and Professor (Biochemist) Soil Science Dep., Univ. of Florida, Gainesville, Florida 32601, respectively.

Received for publication September 20, 1973. Accepted for publication December 19, 1973.