CORRECTION OF CONE INDEX FOR SOIL-WATER CONTENT DIFFERENCES IN A COASTAL-PLAIN SOIL

Soil penetration resistance (cone index) varies with water content. Th e field variation of water content could mask treatment differences. T he correction of cone index data to a single water content would help prevent this. We used equations from TableCurveTM software and from th e literature to correct cone indices for differences in soil water con tents. Data were taken from two field experiments where cotton (Gossyp ium hirsutum L.) was grown using conventional and conservation tillage without irrigation, and beans (Phaseolus vulgaris L.) were grown usin g conventional tillage with microirrigation. Boundary conditions based on hard, dry and soft, wet soils were imposed on the equations. Equat ions fit the data with coefficients of determination ranging from 0.55 to 0.92 and error mean squares from 1.37 to 6.35. After correction, c one index dependence on water content was reduced. A single-equation c orrection did not always fit the data across all treatments. Separate corrections, based on treatment, might be required. When corrections r equired multiple equations, differences may be real or may be a manife station of the correction differences. In this case, the correction ma y not be feasible (unless some future work can coordinate different eq uations and assure a uniform correction). (C) 1997 Elsevier Science B. V.