Investigating the accuracy and comparability of various lime prediction methods for Irish grassland mineral soils

Abstract

Soil pH is a foundational element of agronomy, profoundly influencing biological, chemical and physical soil processes. Adjusting soil pH is a paramount factor for enhancing soil health and productivity with far-reaching environmental benefits. Over time soil naturally tends towards acidity, a process expedited by intensive agriculture practices. To determine the extent of necessary pH corrections, precise soil pH testing is imperative. Various methods including buffer systems, titrations, lime incubations and algorithms considering soil texture are used to assess a soil's lime requirement and each method carries distinct advantages and disadvantages. The Shoemaker–McLean–Pratt (SMP) buffer method is extensively used in Ireland and internationally; however, safety concerns owing to the use of hazardous chemicals required within the method have been highlighted. This study investigates various soil lime requirement tests and compares their performance against a lime incubation study. A proposed alternative to the SMP buffer test for Irish grassland soils is also investigated. Analysis of results obtained indicates that the SMP buffer method demonstrated the highest r² value of .497 when correlated with lime incubation results, while the calcium hydroxide titration method closely aligns with the SMP buffer method with an r² value of .816, followed by the modified Mehlich buffer method with an r² value of .763.