Arduino program for plants care

plant_care.ino

void setup() {
  Serial.begin(57600);
  for(int i = 2; i <= 10; i+=2){
    pinMode(i, OUTPUT);
  }
}

void loop() {

  String s = "";
  for(int i=0; i<5; i++){
    int sensor_value = analogRead(i);
    int led_number = (i*2) + 2;
    if(sensor_value >= 750){
      digitalWrite(led_number, HIGH);
    } else {
      digitalWrite(led_number, LOW);
    }
    s = s + sensor_value + "\t";
  }
  Serial.println(s);

  delay(100);
}