Need help mqtt autodiscovery

When trying to autodetect my MQTT sensor, I get the following messages:

{'identifiers': '246f28b2107c'}, 'unit_of_measurement': 'C', 'icon': 'mdi:alpha-v-circle-outline', 'value_template': "{{value_json['plant']['temp']}}", 'platform': 'mqtt'},)
Traceback (most recent call last):
  File "/usr/src/homeassistant/homeassistant/components/mqtt/sensor.py", line 79, in async_discover_sensor
    config = PLATFORM_SCHEMA(discovery_payload)
  File "/usr/local/lib/python3.8/site-packages/voluptuous/schema_builder.py", line 272, in __call__
    return self._compiled([], data)
  File "/usr/local/lib/python3.8/site-packages/voluptuous/schema_builder.py", line 594, in validate_dict
    return base_validate(path, iteritems(data), out)
  File "/usr/local/lib/python3.8/site-packages/voluptuous/schema_builder.py", line 432, in validate_mapping
    raise er.MultipleInvalid(errors)
voluptuous.error.MultipleInvalid: extra keys not allowed @ data['state_t']

I did take the code from TASMOTA, so?

My mqtt discovery json looks like this:

{
  "name": "TTGO-HIGrow-18-11",
  "state_t": "Tgrow_HIGrow/246f28b2107c",
  "unique_id": "246f28b2107c_temp",
  "dev": {
    "ids": "246f28b2107c"
  },
  "unit_of_measurement": "C",
  "icon": "mdi:alpha-v-circle-outline",
  "value_template": "{{value_json['plant']['temp']}}"
}

and the sensor output looks like this:

{"plant":{"Tgrow_HIGrow":"246f28b2107c","sensorname":"unknown","date":"09-09","time":"21:32","sleep5Count":0,"bootCount":0,"lux":91.66666,"temp":25.1,"humid":51,"soil":2,"salt":0,"bat":139,"batcharge":true,"wifissid":"Enterprise-pro","rel":"2.0.2"}}

what am I doing wrong?