Differential Response of Cotton Growth, Yield and Fiber Quality to Foliar Application of Spirulina platensis and Urea Fertilizer

Aims: Evaluation if foliar spray of destructed cells of Spirulina platensis along with urea fertilizer can contribute to cotton (Gossypium barbadense L. cultivar Giza-94) plant growth, contents of photosynthetic pigments, seed cotton yield, seed index, earliness, lint percent, fineness (Micronair) and strength (Pressely). Study Design: Application of ascending rates of N fertilizer in 3 mainplot treatments and foliar spray with destructed cells of Spirulina platensis in 4 subplot treatments (Contained a non-treated control), with 3 replications. Place and Duration of Study: The Departments of Microbiology and Cotton Research, Sakha Agricultural Research Station, Kafr Elsheikh, Egypt (31º18′30″N & 30º48′14″E) during the two cotton cultivation seasons of years 2016 and 2017. Methodology: Urea (46% N) at 96, 144 or 192 kg N/ha was applied in two equal doses as main-plot treatments. Spirulina platensis was grown and total proteins, contents of 16 amino acids and Fe, K, Mn and P of dried destructed cells were determined and used for foliar application in the rates of 6, 12 or 18 g cells/ha, used as sub-plot treatments. Area of each replicated sub-plot was 12.5 m2. Calcium super phosphate (15% P2O5), potassium sulphate (48% K2O) and Insecticides (when necessary) were supplemented as common treatments. Results: Application of destructed Spirulina increased the plant leaf area, chlorophyll a, b, carotenoids and gibberellin contents, plant height, fruiting branches, open bolls/plant, seed cotton yield and seed index after ginning, fiber length, fineness (Micronair) and strength (Pressely) comparing to the corresponding non-sprayed plants. Urea at 192 kg N/ha along with destructed Spirulina exhibited superiority as enhancers of plant growth, yield and fiber qualities. Conclusion: The dual N/Spirulina combination expressed enhanced cotton growth, yield and qualities of fibers. The tested fertilization strategy is promising for enhanced cotton production economy.