Evaluation of field condition by using smart rice transplanter

Lodging of rice has become a big problem for large scale farmer during harvesting season. Investigating topsoil depth (TD) and apparent electrical conductivity (ECa) of paddy field will be the key to solve this problem. In this study, we developed smart rice transplanter, which could measure TD and ECa. The TD was measured by ultrasonic distance sensor (USS). The ECa was measured by soil electrical conductivity sensor (ECS). We defined that the ECa measured by ECS was soil fertility value (SFV). Each sensor could obtain data every one second. As a result of field test in 2016, total 740,000 of datasets were collected from 50ha paddy. The average of the TD was 19.8 cm while the maximum, minimum, and standard deviation (SD) of TD were 68.47, 7.45 and 6.62 cm respectively. The average of the SFV was 1.04 mS/cm while the maximum, minimum, and SD of SFV were 9.57, 0.07 and 0.68 mS/cm respectively. The result also revealed that high TD was observed in heading area due to machine turning inside the field. In this study, TD and SFV were also applied for variable rate fertilizer application. We designed variable rate ratio with 4 levels. Level 1 where high TD zone reduced by 30%. Level 2 where high SFV zone reduced by 20%. Level 3 where a little high SFV zone reduced by 10%. Level 4 where the other zone fertilized conventional amount. As a result, the smart rice transplanter saved 20% of fertilizer than conventional application