Line Graph with three factors

 # sample 50 values from normal distribution

png(file="plot_nitrogen.png",width=1000,height=650)
p1<-ggplot(mean_subhan1,aes(day,nitrogen,color=Fertilizer.type,shape=Fertilizer.type))
(p1+ geom_line (size=1)+ theme_bw()+
    geom_point(data=mean_subhan1,size=4)+
    s.theme1 + 
    s.theme2+ 
    s.theme3+
    facet +    # third factor
    facect.t + # facet adjustment
  scale_x_continuous(breaks=c(0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27))+
    labs(y=expression(paste("Nitrogen Emission"," ","ug " ," ",cm^-2)),x="Days of Nitrogen Emission Measurment",
         title="",caption=""))
dev.off()