International Soil Tillage Research Organization

Results shown in Table 3 indicate that the mean values of cone indexaveraged for each plowing depth and for each ~nedium depth of plowingdo not differ much. Based on these results the specific draught wascalculated, using the equation (2). For every measured value fourpredicted values were derived by adopting different values of thedraught coefficents K , K2 (from the ESCA and from NIAE field test data)(Oskoui et a1 . , 19831, A comparison between measured and predictedspecific plow draught is given in Fig. 2. It has been found that therewas general over-prediction. The level of over-prediction, shown bymeans of straight approxinlation lines, depends strongly on the type ofplow body used.The largest over-predictions, about 55%, occurred for the KP moldboardbottom. It was found, that prediction was improved when thedraught coefficients of NIAE and cone indices at median depth of plowingwere used, but still there was a considerable discrepancy betweenmeasured and predicted values. Thus, it means, that a need to find amore comprehensive equation, which takes into account different geometricalshapes of moldboard bottoms still remains.In Fig. 3 the experimental relationship between measured specificdraught and cone indices for the KP bottom is shown. Such graphs seem tobe very useful to predict plowing draught, for certain type of plowbody, from cone indices, as long as methods to predict specific plowdraught more accurately, remain elusive.CONCLUSIONS1. In this study, a better agreement between predicted and measuredspecific plow draught occured when NIAE draught coefficients wereadopted.2. The test results presented here confirm that the steepness of themoldboard surface has a noticeable effect on plow draught, especiallyon light soils.3. The proposed method for estimation of plow draught from specific plowdrauqht-cone index ara~hs seems to be useful at Dresent when moreaccuFate methods are not' available.REFERENCESBernacki, H., Haman, J. and Kanafojski Cz., 1967. Teoria i konstrukcjamaszyn rolniczych. t. 1. PWRiL, Warszawa.Bernacki, H., 1975. Nowe techniki uprawy roli. PWRiL, Warszawa.Hencel, A., 1986. Metody wyznaczania oporu pluga na uciag oraz badaniezaleznosci miedzy oporem penetrometrycznynl gleby a oporemjednostkowym pluga. Praca magisterska, AR Szczecin.Oskoui, E.K. and Witney, B.D., 1982. The determination of plough draughtpart 1. Prediction from the soil and meteorological data with coneindex as the soil strength parameter. Journal of Terramechanics,Vol. 19, no. 2, pp. 97-106.Oskoui, E.K., Rackham, D.H. and Witney, B.D., 1982. The determination ofplough draught - part 2. The measurement and prediction of ploughdraught for two mouldboard shapes in the three soil series. Journalof Terramechanics, Vol. 19, no. 3, pp. 153-164.