An assessment of soil structural changes induced by bent leg ploughs

Abstract

The bent leg plough has long been recognised as an excellent conservation tillage tool. It has been claimed that it creates a more porous soil macrostructure without disturbing the residue cover of the soil. There is a need to quantify this property of the tool, so as to assess its potential in creating a soil matrix which yields the maximum water conserving potential. In a field study conducted at Kumulur, South India, two bent leg tool models with 30° and 45° bend angles were tested in a Typic Ustocrept (loamy sand) soil for their ability to induce the desired soil structural changes. The tilled soil structure was encapsulated in wax and a technique was developed to assess the tool's ability in inducing structural changes to soil. The absolute probability of occurrence of different sized clods and voids was computed and simple algebraic models were developed to convert these probabilities into convenient scores, which in turn were used to assess the influence of tool angles, soil compaction and travel speed on the soil manipulating ability of the tool. The results of the experiment showed that an increase in tool speed from 2.0 to 4.0 km h −1 and compaction level from 1.5 to 2.0 MPa (cone index), and a decrease in bend angle from 45° to 30°, could achieve a soil matrix predominantly consisting of clod–void sizes of 1 to 5 mm, which has been considered as suitable for maximising the water conserving potential.