IMPROVEMENT OF PLANOSOL SOLUM .4. FIELD EXPERIMENTS WITH PROTOTYPE ROLL-IN AND DROP-DOWN PLOWS

This paper deals with the design of prototype roll-in and drop-down pl oughs 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 sh owed that the drop-down plough was effective for mixing of the Aw and B horizon of the planosol solum. However, a new problem was encountere d, in that the ploughing of the Aw horizon produced large clods, and t he Ap horizon crumbled and dropped down among the large clods and reac hed lower horizons. The roll-in plough was not effective for soil mixi ng because planosol solum was much harger than the pseudogley soil use d in soil-bin tests in Japan. The roll-in plough bodies simply penetra ted into the soil such as subsoilers do. (C) 1996 Silsoe Research Inst itute