Availability and plant uptake of nutrients following the application of paper pulp and lime to tropical acid soils

Availability and plant uptake of nutrients were evaluated in three tropical acid soils (Kandiudult) amended with paper pulp and lime under greenhouse conditions. Amendments were applied to attain target pH values of 5.5, 6.0. and 6.5. A control treatment (no paper pulp or lime added) was also includ ed. Rye grass (Lolium perenne L.) as a test plant was grown for three succe ssive cycles of 40 days each. Extractable nutrients and cumulative nutrient uptake were determined. The application of paper pulp or lime resulted in a significant increase in exchangeable Ca and K and a decrease in exchangea ble Mg and extractable Fe, Mn, and Zn. Amendment of soils with paper pulp o r lime increased plant uptake of Ca and Mg and decreased that of K, Mn, and Zn. Both amendments behaved similarly, but the effect of lime seemed gener ally greater than that of paper pulp. Paper pulp in tropical acid soils beh aved as a liming agent rather than an organic amendment. Similar to lime, a mendment of soils with paper pulp resulted in an increase in availability o f Ca and Mg and in a decrease in availability of K, Mn, and Zn for plants. Soil extractions appeared to be appropriate for assessing the availability of Ca, Mn, and Zn. Soil pH and effective cation exchange capacity positivel y influenced the availability of Ca and negatively the availability of Mn a nd Zn. Thus, the precision of predicting nutrient availability in paper pul p amended tropical acid soils could be improved by including soil pH or eff ective cation exchange capacity in relevant regression equations.