A liquid application apparatus for applying liquid to soil during a planting operation, comprising: a seed firmer (2700, 3100) mounted to a planter row unit, the planter row unit having an opening system and a closing system, the opening system comprising two opening disks rollingly mounted to a downwardly-extending shank and configured to open a v-shaped planting trench defined by first and second sidewalls in the soil, the closing system including one or more closing wheels pivotally coupled to the row unit and configured to close the planting trench opened by the opening system, the planter row unit depositing seeds in the open planting trench forward of the closing system and between said first and second sidewalls as the planter row unit traverses the field, the seed firmer (2700, 3100) resiliently engaging a bottom portion of said open planting trench after the seeds are deposited and forward of said closing system, said seed firmer (2700, 3100) having a first wing (2730-1, 3132-1) disposed to open a first transversely-extending side trench in said first sidewall as the planter row unit traverses the field; and a first liquid injection conduit (2734-1, 3152-1) mounted to said seed firmer (2700, 3100) and disposed to inject liquid into said first transversely-extending side trench after the seeds are deposited and forward of the closing system, wherein the seed firmer (2700, 3100) has a firmer body (2710, 3110) including: a tail portion; a flexible portion (2720, 3112) for maintaining a resilient downward force on the tail portion as the seed firmer (2700, 3100) traverses the soil; and a ground-engaging portion mounted to the tail portion and disposed to engage the planting trench and firm the previously deposited seeds at the bottom of the planting trench into the soil forward of the closing system; wherein an outlet of said first liquid injection conduit (2734-1, 3152-1) is laterally spaced from a transverse center of said firmer body (2710, 3110) by a distance to avoid burning the previously deposited seeds at the bottom of the planting trench when the liquid is injected by said first liquid injection conduit (2734-1, 3152-1). a seed firmer (2700, 3100) mounted to a planter row unit, the planter row unit having an opening system and a closing system, the opening system comprising two opening disks rollingly mounted to a downwardly-extending shank and configured to open a v-shaped planting trench defined by first and second sidewalls in the soil, the closing system including one or more closing wheels pivotally coupled to the row unit and configured to close the planting trench opened by the opening system, the planter row unit depositing seeds in the open planting trench forward of the closing system and between said first and second sidewalls as the planter row unit traverses the field, the seed firmer (2700, 3100) resiliently engaging a bottom portion of said open planting trench after the seeds are deposited and forward of said closing system, said seed firmer (2700, 3100) having a first wing (2730-1, 3132-1) disposed to open a first transversely-extending side trench in said first sidewall as the planter row unit traverses the field; and a first liquid injection conduit (2734-1, 3152-1) mounted to said seed firmer (2700, 3100) and disposed to inject liquid into said first transversely-extending side trench after the seeds are deposited and forward of the closing system, wherein the seed firmer (2700, 3100) has a firmer body (2710, 3110) including: a tail portion; a flexible portion (2720, 3112) for maintaining a resilient downward force on the tail portion as the seed firmer (2700, 3100) traverses the soil; and a ground-engaging portion mounted to the tail portion and disposed to engage the planting trench and firm the previously deposited seeds at the bottom of the planting trench into the soil forward of the closing system; a tail portion; a flexible portion (2720, 3112) for maintaining a resilient downward force on the tail portion as the seed firmer (2700, 3100) traverses the soil; and a ground-engaging portion mounted to the tail portion and disposed to engage the planting trench and firm the previously deposited seeds at the bottom of the planting trench into the soil forward of the closing system; wherein an outlet of said first liquid injection conduit (2734-1, 3152-1) is laterally spaced from a transverse center of said firmer body (2710, 3110) by a distance to avoid burning the previously deposited seeds at the bottom of the planting trench when the liquid is injected by said first liquid injection conduit (2734-1, 3152-1).