> growth<-c(33.3,47.8,44.4,42.9,40.9,35.5,35.5,35.4,47.6,38.8,29.6,33.4,32.8,38.8,42.8,38.5,42.4,45.5,38.9,38.9,44.5)
> dung<-rep(LETTERS[1:4],c(6,4,5,6))
> dung<-factor(dung)
> agro<-data.frame(dung,growth)
> analyse<-aov(growth~dung, agro)
> analyse
Call:
   aov(formula = growth ~ dung, data = agro)

Terms:
                    dung Residuals
Sum of Squares  113.7990  408.5105
Deg. of Freedom        3        17

Residual standard error: 4.902043 
Estimated effects may be unbalanced
> summary(analyse)
            Df Sum Sq Mean Sq F value Pr(>F)
dung         3 113.80   37.93  1.5786 0.2313
Residuals   17 408.51   24.03               
> summary(agro)
 dung      growth     
 A:6   Min.   :29.60  
 B:4   1st Qu.:35.50  
 C:5   Median :38.90  
 D:6   Mean   :39.44  
       3rd Qu.:42.90  
       Max.   :47.80