THE EFFECTS OF CALCIUM-CARBONATE AND CALCIUM HYDROXIDE ON PLANT-GROWTH DURING OVERLIMING

Contradictory results concerning the effects of heavy liming have been reported in South Africa for greenhouse studies on a variety of crops using different liming materials. The current study addresses this co ntroversy by investigating the consequences of overliming in maize and wheat growth using calcium carbonate and calcium hydroxide as liming materials, Growth media used include quartz sand and two acid oxisols (high and medium buffered) to which phosphorus was applied before and after the lime soil equilibration. The phase equilibria of soil phosph orus were also investigated. Growth media, crop, liming material, and manner of phosphorus fertilization all have a significant influence on plant production during overliming studies and may account for the di verse observations reported in the Literature. Soil chemistry and plan t symptoms indicate that plant physiological effects induced by a more reactive Lime source such as calcium hydroxide may play as prominent a role in the outcome of overliming as nutrient deficiencies.