This paper presents a summary of three experiments and discusses suggestions and observations made over the past 6-years of deep placement studies. Deep banding of a low concentration of potassium from 611-1511 deep in the drill approximately 211 wide over several years can correct subsoil nutrient deficiencies.

Results of these studies suggest that subsoiling is needed with deep placement for potassium to significantly increase lint yields in the deep band. Taproot length was also increased with deep banded potassium applications, DES 119 (of the 4 varieties studied) responded best to deep banded potassium. The deep 160 lb K₂O treatment on DES 119 produced significantly higher lint yields than all 3 surface broadcast incorporated (80, 120, and 160 lb K,O/A) treatments. All nine potassium application treatments significantly increased yields of DES 119, DP 50, St 453, and C-130 in a 3-year study. Lint yields were enhanced by a combination of nitrogen and potassium when applied at the higher rates studied.

Subsoil samples (611-1211 or preferably 611-1511 deep) should be taken to assess the problems in the subsoil, before considering deep banding. A subsoil pH of 5.7 or higher is desirable or correction with a prilled lime and potassium blend may be needed. Rows should be hipped prior to and immediately after deep banding to minimize drying out of the seedbed. Non-irrigated cotton requires higher soil test K values than irrigated cotton. Subsoil potassium deficiencies can be corrected more rapidly with deep banding than by surface applications.