Starter fertilizer (ammonium polyphosphate) was evaluated in combinations with Donlar DXL-500 beta protein biopolymer for their effects on crop nutrient management and cotton production. Six treatments combinations involving 1 to 3 qt/acre of DXL500 with and without 10 gal/acre of ammonium polyphosphate (10-34-0, 12.4 lb N/acre, 18.4 lb P/acre) starter fertilizer were studied at two locations in the Mississippi Delta. The first study (8 replications) was located on the Delta Research and Extension Center (DREC) at Stoneville, MS on a Bosket very fine sandy loam (Mollic Hapludalfs) grown with irrigation. The second study (10 replications) was located on the Tribbett Satellite Farm (TSF) at Tribbett, MS on a Forestdale/Dundee silty clay loam (Typic Ochraqualfs/Aeric Ochraqualfs) and grown without irrigation. For each study, nitrogen (N) was applied at a total rate of 120 lb N/acre as urea-ammonium nitrate solution (32% N, 3.54 lb N/gal) with one-half of the total N applied prior to planting and the remainder as a sidedress application at beginning bloom. Cultural practices such as weed and insect control, cultivation, and defoliation were maintained uniformly across all treatments but were specific for each location. Seedcotton was harvested from the center two rows of each 4-row plot. Random grab samples were taken from each plot and ginned to determine the lint yield. At TSF, total seedcotton yields ranged from 2970 to 3066 lb/acre and lint yields from 1092 to 1112 lb/acre. There was no significant difference between any of the treatments and no response to either starter fertilizer or the DXL-500. With respect to the DREC study, total seedcotton yields ranged from 3978 to 4074 lb/acre and lint yields ranged from 1541 to 1602 lb/acre. The irrigated cotton on the sandy loam at DREC had yields which were 41 to 44 % higher than the non-irrigated yields at TSF on the silty clay loam. There was no significant differences among the DXL-500 treatments or the starter fertilizer plus DXL-500 treatments. Under the conditions evaluated, which were quite diverse, the was no benefit from either ammonium poly-phosphate starter fertilizer or Donlar DXL-500.