First of all you should realize whether the soft keyboard is active or not - Use the following command from your code to check "mInputShown" parameter - If "true" - Active Soft Keyboard.
adb shell dumpsys input_method | grep mInputShown
Use this code for hiding the native keyboard in Java-appium running older versions of appium.
driver.navigate().back()
P.S - The adb command is useless for emulators as the flag whose value is being checked is always set to true, whether your keyboard is active or not.