Cotton Response to Phosphorus Applications with and without AVAIL® Phosphorus Fertilizer Enhancer.

A multi-year field study (2010-2012) was established at the Tribbett Satellite Farm of the Delta Research and Extension Center to evaluate cotton lint yield response to fertilizer phosphorus (P) applications in a rain-fed environment.  The soil type is a Forestdale-Dundee complex (Typic Endoaqualfs).  Fertilizer P was applied annually at rates of 0, 22.4, 50.1, and 67.1 kg P/ha (0, 20, 40, and 60 lb P/acre) as concentrated superphosphate (0-46-0) alone or amended with AVAIL^® Phosphorus Fertilizer Enhancer (Specialty Fertilizer Products, LLC) at a rate of 2.08 liter/mt (0.5 gal/ton).  The experimental design was a randomized complete block with six replications.  Plots consisted of four 102-cm rows, 22.86 m in length.  In the first year, the P treatments were spring-applied and incorporated.  After the first year, the P was fall applied prior to any field operation.  The nitrogen rate (167 kg N/ha) and all other cultural practices were maintained uniformly across the field.  Grab seedcotton samples were collected at harvest from each plot and then ginned (10-saw micro-gin) to determine lint percentage and then lint yield.  Soil samples from each plot were taken after harvest to monitor changes in soil test P.  There was no significant response to P rate or AVAIL in either 2010 or 2011.  Main effects in 2010 did show a slight trend toward a yield response with AVAIL when averaged across all P rates but the trend was not evident in 2011.  Since this study relies on rainfall, the 2011 yields (646 kg/ha) were about 45% of the 2010 yields (1429 kg/ha).  The 2012 yields were more in line with 2010 but again no significant response to added P or AVAIL.  Soil test P levels are increasing slightly with the fertilizer P additions.  The study is continuing to evaluate P buildup and potential long-term effects.