7/2/2013 - By Dr. Travis Shaddox

The topic of my blog article last month was staining from granular fertilizer and it may be viewed here, http://www.harrells.com/blog/fertilizer-stains.  This month I decided to fill in the remaining piece to the staining puzzle by discussing liquid fertilizer.

Generally, staining from liquid fertilizer is less of an issue than from granular fertilizers.  This is largely due to the broad distribution of fertilizer across a wide area.  However, raw materials used to create liquid fertilizer can be the same as granular fertilizer.  Based upon last month’s results, we are interested in liquids containing any form of sulfated metal, particularly iron, manganese, or magnesium.

Study

Sixteen liquid fertilizers were applied to dry cement pavers and treated lumber.  Labels for each fertilizer may be found on http://www.harrells.com.  Each fertilizer was applied twice at a rate of 10X the high labeled rate and the paver or wood was allowed to dry for 48 hours before photographs were taken.  Results for cement pavers and treated lumber can be seen in Figure 1 and Figure 2, respectively.  Of the sixteen products tested, only the 12-0-0 and Long Iron produced any visible stain at 20X the high labeled rate.  Based upon these results, every Harrell’s Max product except 12-0-0 and Long Iron may be safely applied to cement or wood up to 20X the highest labeled rate without concern of staining.

Please keep in mind, application water can have a significant influence on nutrient availability, thus, differing results could occur with different application water.

Figure 1. Cement pavers showing stains from 16 liquid fertilizers.

Figure 2. Treated lumber showing stains from 16 liquid fertilizers.