Unable to Send SMS from Arduino using SIM900A GSM module

Sms not sending by Arduino to mobile.
My program is here

#include<LiquidCrystal.h>
#include<dht.h>

#define dht_dpin A1
#define LUX A0
LiquidCrystal lcd(2,3,4,5,6,7);

dht DHT;

#define light 10
#define fan 8
#define spray 11
#define motor 12
#define soil 9

int temperature, humidity, temp,Temp;
int check;
int test,test1,test2,test3;
float volt,lux,value;
int tempflag=0,humflag=0,lightflag=0;
byte degree[8] =
              {
                0b00011,
                0b00011,
                0b00000,
                0b00000,
                0b00000,
                0b00000,
                0b00000,
                0b00000
              };

void setup()
{
  Serial.begin(9600);
  lcd.begin(16,2);
 
  pinMode(soil, INPUT);
  pinMode(light, OUTPUT);
  pinMode(fan, OUTPUT);
  pinMode(spray, OUTPUT);
  pinMode(motor, OUTPUT);
 
  lcd.createChar(1, degree);
  lcd.setCursor(0,0);
  lcd.print("Green House");
  lcd.setCursor(0,1);
  lcd.print("Monitering");
  delay(2000);
  lcd.clear();
  lcd.setCursor(0,0);
  lcd.print("AGRI PROJECT");
  lcd.setCursor(0,1);
  lcd.print("By S K CHHAYA");
  delay(2000);
  lcd.clear();
}

void loop()
{
  /*-----Light Intensity------*/
 
  DHT.read11(dht_dpin);
  lcd.clear();
  lcd.setCursor(0,0);
  lcd.print("Humidity=");
  lcd.setCursor(0,1);
  lcd.print(humidity=DHT.humidity);
  lcd.print(" %");
  delay(2000);
  lcd.clear();
  lcd.setCursor(0,0);
  lcd.print("Light: ");
  lcd.setCursor(0,1);
  lcd.print(lux);
  delay(2000);
  lcd.clear();
  lcd.setCursor(0,0);
  lcd.print("Temperature=");
  lcd.setCursor(0,1);
  lcd.print(temperature=DHT.temperature);
  lcd.write(1);
  lcd.print(" C");
  delay(2000);
  lcd.clear();
  value=analogRead(LUX);
  volt=(value/1023.0)*5;
  lux=((2500/volt)-500)/3.3;
  delay(10);
  
   if(lux<100)
   {
     digitalWrite(light, HIGH);
      if (lightflag==0)
  {
     Serial.println("AT+CMGF=1");\
     Serial.println("AT+CMGS=\"9784398922\"");
     Serial.println("LOW LIGHT");
     Serial.println("TURN ON LIGHT");
     Serial.print("Light Intensity: ");
     Serial.print(lux);
     Serial.println(" LUX");
     Serial.print("Temperature: ");
     Serial.print(temperature);
     Serial.println(" Degree Celsius");
     Serial.print("Humidity: ");
     Serial.print(humidity);
     Serial.println(" %");
     Serial.write(26);
   lightflag=1;
  }
     lcd.clear();
     lcd.setCursor(0,0);
     lcd.print("Low light ");
     lcd.print(lux);
     lcd.print(" LUX");
     lcd.setCursor(0,1);
     lcd.print("Lights turned ON");
     check=1;
     test=1;
     delay(2000);
   }
   else
   {
    if(check==1)
    {
        if (lightflag==1)
  {
     Serial.println("AT+CMGF=1");\
     Serial.println("AT+CMGS=\"9784398922\"");
     Serial.print("LIGHT TURNED OFF");
     Serial.print("Light Intensity: ");
     Serial.print(lux);
     Serial.println(" LUX");
     Serial.print("Temperature: ");
     Serial.print(temperature);
     Serial.println("degree Celsius");
     Serial.print("Humidity: ");
     Serial.print(humidity);
     Serial.println(" %");
     Serial.write(26);
  lightflag=0;
  }
     check=0;
     lcd.clear();
     lcd.setCursor(0,0);
     lcd.print("light int: ");
     lcd.print(lux);
     lcd.print(" LUX");
     lcd.setCursor(0,1);
     lcd.print("Lights turned OFF");
    }
     digitalWrite(light, LOW);
     test=0;
     delay(2000);
   }
  
   if(temperature > 40)
  {
    digitalWrite(fan, HIGH);
    if (tempflag==0)
    {
     Serial.println("AT+CMGF=1");\
     Serial.println("AT+CMGS=\"9784398922\"");
     Serial.println("TEMPERATURE INCREASES FROM CRITICAL LEVEL");
     Serial.println("FAN TURNED ON");
     Serial.print("Light Intensity: ");
     Serial.print(lux);
     Serial.println(" LUX");
     Serial.print("Temperature: ");
     Serial.print(temperature);
     Serial.println("degree Celsius");
     Serial.print("Humidity: ");
     Serial.print(humidity);
     Serial.println(" %");
     Serial.write(26);
     tempflag=1;
    }
     lcd.clear();
     lcd.setCursor(0,0);
     lcd.print("Temp increases");
     lcd.setCursor(0,1);
     lcd.print("Fan Turned ON");
     delay(2000);
     lcd.clear();
     lcd.setCursor(0,0);
     lcd.print("Temperature");
     lcd.setCursor(0,1);
     lcd.print(temperature);
     lcd.write(1);
     lcd.print("C");
     check=2;
     test2=1;
     delay(2000);
   }
   else
   {
    if(check==2)
     {
        if (tempflag==1)
    {
     Serial.println("AT+CMGF=1");\
     Serial.println("AT+CMGS=\"9784398922\"");
     Serial.println("FAN TURNED OFF");
     Serial.print("Light Intensity: ");
     Serial.print(lux);
     Serial.println(" LUX");
     Serial.print("Temperature: ");
     Serial.print(temperature);
     Serial.println("degree Celsius");
     Serial.print("Humidity: ");
     Serial.print(humidity);
     Serial.println(" %");
     Serial.write(26);
     tempflag=0;
    }
     check=0;
     test1=0;
    }
   digitalWrite(fan, LOW);
   delay(1000);
   }
 
  if(humidity < 30)
  {
     digitalWrite(spray, HIGH);
     if (humflag==0)
     {
     digitalWrite(13, HIGH);
     Serial.println("AT+CMGF=1");\
     Serial.println("AT+CMGS=\"9784398922\"");
     Serial.println("HUNIDITY INCREASES FROM DEFINED LEVEL ");
     Serial.println("SPRAY TURNED ON");
     Serial.print("Light Intensity: ");
     Serial.print(lux);
     Serial.println(" LUX");
     Serial.print("Temperature: ");
     Serial.print(temperature);
     Serial.println("degree Celsius");
     Serial.print("Humidity :");
     Serial.print(humidity);
     Serial.println(" %");  
     Serial.write(26);
     humflag=1;
     }
     lcd.clear();
     lcd.setCursor(0,0);
     lcd.print("Humidity increas");
     lcd.setCursor(0,1);
     lcd.print("Spray Turned ON");
     delay(2000);
     lcd.clear();
     lcd.setCursor(0,0);
     lcd.print("Humidity");
     lcd.setCursor(0,1);
     lcd.print(humidity);
     lcd.print(" %");
     check=3;
     test2=1;
     delay(2000);
   }
   else
   {
    if(check==3)
    {
    if (humflag==1)
    {
     Serial.println("AT+CMGF=1");\
     Serial.println("AT+CMGS=\"9784398922\"");
     Serial.println("SPRAY TURNED OFF");
     Serial.print("Light Intensity: ");
     Serial.print(lux);
     Serial.println(" LUX");
     Serial.print("Temperature: ");
     Serial.print(temperature);
     Serial.println("degree Celsius");
     Serial.print("Humidity: ");
     Serial.print(humidity);
     Serial.println(" %");
     Serial.write(26);
     humflag=0;
    }
     check=0;
    }
     digitalWrite(13, LOW);
     digitalWrite(spray, LOW);
     test2=0;
     delay(2000);
  }
  
   if(digitalRead(soil)==1)
   {
    digitalWrite(motor, HIGH);
    Serial.println("AT+CMGF=1");\
     Serial.println("AT+CMGS=\"9784398922\"");
     Serial.println("WATER REQUIRED ");
     Serial.println("MOTOR TURNED ON ");
     Serial.print("Light Intensity: ");
     Serial.print(lux);
     Serial.println(" LUX");
     Serial.print("Temperature: ");
     Serial.print(temperature);
     Serial.println("degree Celsius");
     Serial.print("Humidity: ");
     Serial.print(humidity);
     Serial.println(" %");
     Serial.write(26);
     check=4;
     test3=1;
     lcd.clear();
     lcd.setCursor(0,0);
     lcd.print("Water Required");
     lcd.setCursor(0,1);
     lcd.print("Motor turned ON");
     delay(2000);
   }
    
  else
  {
    if(check==4)
    {
     Serial.println("AT+CMGF=1");\
     Serial.println("AT+CMGS=\"9784398922\"");
     Serial.println("WATER REQUIRED ");
     Serial.println("MOTOR TURNED OFF ");
     Serial.print("Light Intensity: ");
     Serial.print(lux);
     Serial.println(" LUX");
     Serial.print("Temperature: ");
     Serial.print(temperature);
     Serial.println("degree Celsius");
     Serial.print("Humidity: ");
     Serial.print(humidity);
     Serial.println(" %");
     Serial.write(26);
     check=0;
    }
     digitalWrite(motor, LOW);
     test3=0;
  }
     delay(100);
}

There should be a delay after AT+CMGS==xxx command.
You should wait for the > prompt given by module after AT+CMGS command is executed.
You are just sending one statement after another without waiting for the prompt.