Creating a variable in R to fill in data by factor/level from another data frame

Here's my main dataset:

plot_no <-c(1,1,1,2,2,2,3,3,3,3,3)
basal_area <-c(3.5,4.1,6.0,0.9,4.4,4.8,0.7,3.2,3.6,5.5,1.8)
indiv_tree <-c(1,2,3,1,2,3,1,2,3,4,5)

df1<-data.frame(plot_no, basal_area, indiv_tree)

which looks like this:

 plot_no basal_area indiv_tree
1        1        3.5          1
2        1        4.1          2
3        1        6.0          3
4        2        0.9          1
5        2        4.4          2
6        2        4.8          3
7        3        0.7          1
8        3        3.2          2
9        3        3.6          3
10       3        5.5          4
11       3        1.8          5

In another data frame I have summed the total basal_area for each plot_no, and these data are now in a data frame that looks like this:

  plot_no total_basal
1       1        13.6
2       2        10.1
3       3        14.8

What I want to do is code a new variable in df1 where the total_basal value would match up with the plot_no value, producing this:

   plot_no basal_area indiv_tree total_basal
1        1        3.5          1        13.6
2        1        4.1          2        13.6
3        1        6.0          3        13.6
4        2        0.9          1        10.1
5        2        4.4          2        10.1
6        2        4.8          3        10.1
7        3        0.7          1        14.8
8        3        3.2          2        14.8
9        3        3.6          3        14.8
10       3        5.5          4        14.8
11       3        1.8          5        14.8

I took a look at this question Create new variable in R data frame by conditional lookup but I suspect there's a simpler, more basic solution.