USE OF NEW CONE UPLAND PENITROMETER FOR SOIL STRENGTH MEASUREMENTS OF RED YELLOW PODZOLIC SOIL UNDER FOREST COVER

Soil resistance to penetration or penetrability, which is measured by thepenitrometer, has found numerous engineering and agronomic applications.The instrumentation and procedure are fairly simple and rapid, relatively nondestructivedeterminations are possible both in the field and the laboratory.The force or the work required to drive one of standard metal heads to agiven depth has been found empirically to be correlated with soil depth, bulkdensity and moisture content. The information obtained is interpreted tomake diagnoses or predictions regarding soil bearing strength andtrafficability, degree of compaction, workability by agricultural implementsand the consequences of tillage in terms of soil condition and crop yield.Different types of penitrometers with spring loaded or provingOring types arein common use. But these instruments are not suitable for local soilconditions due to inappropriate spring mechanism. It also requires high costfor calibration process.A hammer type low cost appropriate mechanical 'PLAG Uplandpenitrometer' was designed and constructed. (Patent no: 13360). It consistsof a carriage probe unit, one force applied unit and adjustable mainframe. Itwas used forr soil strength measurements of Red yellow Podzolic soil underforest cover in six different layers with ten replications.The results show that the average soil strength values of the 2.5cm, 7.5 cm,12.5cm, 17.5cm, 22.5cm and 27.5cm depth layers were 0.7M pa, 1.2M pa,1.3M pa, 1.3M pa, 1.7 M pa and 1.6M pa respectively. The overall averagesoil strength of Red yellow Podzolic soil under forest cover was 1.3M pa andthe cost of production of the design 'PLAG Upland penitrorneter' was 10,000rupees