FIG 4.

Abundances of 16S rRNA genes, enumerated by qPCR, on radish taproot surfaces (n = 3) grown in loamy sand (LS) and silty clay loam (SCL) mixed with amendment from antibiotic-treated beef cattle (BA), antibiotic-free beef cattle (BC), antibiotic-treated dairy cattle (DA), or antibiotic-free dairy cattle (DC) or mixed with chemical fertilizer only as a control. Standard errors are indicated by the error bars. Significant differences (P < 0.050, survival analysis) are indicated as follows: #, for the same amendment, the soil texture that yielded significantly greater gene abundance; ^, for the same soil texture, amendments that yielded gene abundances significantly different from those of the fertilizer control; +, for the same cattle type (beef or dairy), same amendment type, and same soil texture, the antibiotic condition (antibiotic or control) that yielded significantly greater gene abundance. The letters A and B indicate statistical groupings for the effect of amendment type (manure, static compost, and turned compost) for the same cattle and same soil texture.