Improvement of Planosol Solum: Part 4, Field Experiments with Prototype Roll-In and Drop-Down Ploughs

Abstract This paper deals with the design of prototype roll-in and drop-down ploughs and field tests on a planosol solum in China to obtain mixing of the second (Aw) and third (B) horizons to improve the planosol solum, leaving the first (Ap) horizon undisturbed. The field test results showed that the drop-down plough was effective for mixing of the Aw and B horizon of the planosol solum. However, a new problem was encountered, in that the ploughing of the Aw horizon produced large clods, and the Ap horizon crumbled and dropped down among the large clods and reached lower horizons. The roll-in plough was not effective for soil mixing because planosol solum was much harger than the pseudogley soil used in soil-bin tests in Japan. The roll-in plough bodies simply penetrated into the soil such as subsoilers do.