Taking into consideration that potential evapotranspiration normally exceeds the growing season rainfall and that a water shortage can occur unless a reserve of soil water is stored before the crop is planted, it can be concluded that the amount of stored soil water at sowing time is a critical factor in the success of dryland cropping systems. The main aim of this investigation was to know if interaction chi 2 test is a valuable tool, when taking into account stored soil (0-60 cm depth) water at sowing time and maize grain yield, in making decision for sowing or not sowing at a given time. Data on the amount of soil water at sowing time and maize grain yield from four experiments carried out during 2001 and 2002 at the Ejido Francisco Villa, Lerdo, Durango, Mexico were used to run the interaction chi 2 tests. For a minimum maize yield of 1000 kg ha -1, the following level of stored soil water was defined as critical: 8.34 cm for cv. 'Blanco Hualauises' and cv. 'H-412'. The interaction chi 2 test is a good tool to determine soil water critical levels at the sowing time of maize to ensure success in the present dryland cropping system.
