mpl2 <- update(mpl1, . ~ . - rack) # model without rack
mpl3 <- update(mpl1, . ~ . - status) # model without status
mpl4 <- update(mpl1, . ~ . - amd:nutrient) # without amd:nutrient interaction
ICtab(mpl1,mpl2,mpl3,mpl4, type = c("AICc"))
#     dAICc df
# mpl1  0.0  10
# mpl4  1.4  9 
# mpl3  1.5  8 
# mpl2 55.0  9