Mobilization of Agricultural Machines Based on Crop Calender for Rice Cultivation in Grobogan District, Central Java. Agricultural machines for rice production in Central Java especially Grobogan District are already intensively developed, but their utilization is still low. Optimalization use of those agricultural machines is needed to improve their performances. This research aimed: (i) To arrange mobilization concept of agriculturalmachines in order to optimize their use for rice cultivation in Grobogan District, and (ii) To analyze the deficit and working capacity of those agricultural machines after optimalization use through their mobilization. This research was focused on hand tractors and power threshers only, and was conducted in Grobogan District, in 2013. Data on lowland area and population of hand tractor and power thresher were collected from agricultural office of Grobogan District and its Sub-districts, meanwhile data dealing with agricultural machine's performances were collected through interview with agricultural machines owner and UPJA using well structured questioners. The collected data were arranged in the form of table and map, and then analyzed using requirement and mobilization analyses. The results showed that through mobilization scenario of 20% available agricultural machines among sub-district with four different planting times in Grobogan District could improve the machine's performance and could reduce their deficit. By mobilizing those agricultural machines for rice cultivation in Grobogan District, their deficit could be reduced up to >50%, meanwhile, working capacity of those machines could be increased from < 30 ha/year/unit before mobilization become 35,5 ha/year/unit after mobilization.