db-RDA in vegan package do not evaluate all explanatory variables

Question

These days I am trying to develop a db-RDA analysis on the vegan package. I have 24 explanatory variables and 46 samples. The problem is that when developing the db-RDA I only get results for the first 7 environmental variables regardless of the order in which they are arranged. What can be the reason? I explain the problem with the code

#1 I charge the package vegan

library(vegan)

#2 I upload the OTU data frame and I adapted in the correct format

featuretable16 <-read.table(file = '16Sfeaturetable.txt', sep = '\t', header = TRUE)
featuretable162 <- featuretable16[,2:57]
row.names(featuretable162) <- featuretable16$Rep
ft16stransponed <- t (featuretable162)

#3 I upload the environmental conditions and I adapted in the correct format (explanatory variables)

ambiental16 <-read.table(file = 'environmental16.txt', sep = '\t', header = TRUE)
rownames (ambiental16) = ambiental16$SampleID
ambiental162 <- ambiental16[,2:24]

#4 Perform the dbrda analysis and plotting and only appeared the first 7 explanatory variables

dbrda <- dbrda(ft16stransponed ~ ., ambiental162, dist="bray")
plot(dbrda)

db-RDA plot

#5 I performed the significance with ANOVA. Although the analysis evaluated all the environmental factors only show the results of the first seven explanatory variables.

anova(dbrda, by="terms", permu=999) 
Permutation test for dbrda under reduced model
Terms added sequentially (first to last)
Permutation: free
Number of permutations: 999

Model: dbrda(formula = ft16stransponed ~ time + Location + pH + DO + Conductivity + Temperature + Water.Flow + Water.depth + Nitrogen + Nitrate + Ammonium + Phosphorus + TOC + Amoxicillin + Azithromycin + Ciprofloxacin + Clarithromycin + Erythromycin + Lincomicina + Metronidazol + Sulfametoxazol + Ofloxacino + Trimetoprima, data = ambiental162, distance = "bray")
             Df SumOfSqs       F Pr(>F)    
time          1   0.6731  3.5504  0.004 ** 
Location      1   4.7222 24.9074  0.001 ***
pH            1   0.9193  4.8488  0.002 ** 
DO            1   0.6811  3.5926  0.004 ** 
Conductivity  1   0.5441  2.8700  0.004 ** 
Temperature   1   0.6336  3.3418  0.004 ** 
Water.Flow    1   0.9761  5.1486  0.001 ***
Residual     48   9.1003                   
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1
> 

I made a R notebook too, but I don´t how I can submit here but could be more clear.