IMPROVING PHOSPHORUS NUTRITION OF COTTON

Crop recovery of applied Phosphorus (P) fertilizer can be low, especially during season of low soil temperature, which decreases plant root growth and nutrient uptake. The H₂PO₄^- or HPO₄^-2 anions readily react with soil cations such as Calcium (Ca), Magnesium (Mg), iron (Fe) and Aluminum (Al) to produce various phosphate compounds of very limited water solubility. Specialty Fertilizer Products (SFP), Leawood, KS, USA has developed and patented a product registered as AVAIL® that is reported to attract and sequester antagonistic cations out of the soil solution leaving more of applied P in available form for plant uptake. To evaluate effectiveness of AVAIL product for cotton production, experiments were conducted in two locations in West Tennessee, Grand Junction (GJ) in Hardeman County and Ames Plantation (AP) located in Fayette County. Treatments consisted of applying Mono-Ammonium Phosphate (MAP, 11-52-0) alone or coated with AVAIL at rates of 34 or 68 kg ha^-1 P₂O₅. A no P check was also included. An additional treatment consisting of AVAIL treated P in combination with Nutrisphere-N®, a Nitrogen (N) stabilizer product offered by SFP, was also included. At GJ site, when averaged over P rates and years, AVAIL treated MAP improved tissue P concentration and increased cotton lint yield by 157 kg ha^-1 over untreated MAP. At AP site, when averaged over years and P rates, application of AVAIL treated MAP increased cotton lint yield by 85 kg ha^-1 over untreated MAP. In both experiments, 34 kg ha^-1 AVAIL treated MAP produced higher tissue P concentrations and greater yields than 68 kg ha^-1 without AVAIL. Influencing reactions in the micro-environment around the fertilizer granule has proven to have a significant benefit on the yield and P uptake of cotton. More research is needed to determine P content in the soil and further improve fertility recommendations.