improvement of clod size in tillage through six sigma methodology

the aim followed in tillage operations is the preparation of a suitable seedbed. the clod mean weight diameter (mwd) is one of the important tillage quality factors. in this study six sigma methodology was employed to improve the mwd index on the experimental farm of the university of tehran. six sigma is considered as one of the new improving process methods that has gained wide applications in almost all sciences. measurements indicated the process capability (cpk) to be 0.69 for wmd in the case study. data also revealed that the process was out of control and needed improvement. fmea revealed that soil moisture content, plowing speed and plowing depth are the most important factors affecting clod size, with 900, 630 and 560 risk priority number respectively. these factors were reformed in the new process and cpk measured again. cpk in the new process was obtained as 1.36 indicating that the process became adequately applicable. utilization of six sigma caused the improvement of tillage quality and the preparation of a suitable seedbed.