Effect of hormone enriched polymer coated phosphatic fertilizer on growth, yield and phosphorus use efficiency of wheat (Triticum aestivum L.) under normal and stress conditions

Abstract

The efficiency of applied P fertilizers is very low in alkaline soils. There is a need to adopt certain economical approaches to enhance uptake of P from applied P fertilizer. Coating of diammonium phosphate (DAP) granules with polymer can improve P availability. This technique can further be improved by the addition of certain hormones with the objective of strengthening plant defense against stresses. Plant hormones are considered necessary endogenous molecules which are involved in regulating plant development. A series of experiments were conducted to investigate the efficacy of hormones enriched polymer-coated diammonium phosphate on yield, growth and phosphorus use efficiency of wheat (Triticum aestivum L.) under normal and saline soils. In laboratory experiments the organic copolymer amended with calcium acrylamide (CCA) with different concentrations (0, 1, 1.5, 2%) was coated on DAP to check the release pattern of P in saline and non-saline soils over different intervals. Selected best concentration of CCA (1%) was mixed with growth regulators, L tryptophan at 10 and 20 mg L-1 , L-methionine at 1 and 5 mg L-1 and salicylic acid at 5 and 10 mg L-1 and coated on DAP fertilizer to investigate P and hormones release in both soils. The best selected polymer (1% concentration) and hormones L-methionine (5 mg L-1 ), L tryptophan (20 mg L- 1 ), and salicylic acid (10 mg L-1 )} was mixed separately and coated on DAP fertilizer granules for P release at different moisture levels (50, 75 and 100% of FC) and temperatures (10, 25 and 40°C) up to two months, keeping alone polymer-coated or uncoated DAP as control. Hormones enriched polymer-coated DAP (HPCDAP), polymer coated DAP (PCDAP) and uncoated DAP were applied @ of 1 g in 100 g-1 soil in plastic cups containing 200 g soil. Selected best concentrations of hormones {L-tryptophan (20 mg kg-1 ), salicylic acid (10 mg kg-1 ) and L-methionine (5 mg kg-1 )} from the previous experiments were mixed in combination with polymer to prepare a solution in distilled water and coat on DAP granules. This hormones enriched polymer solution was coated on DAP, and fertilizer was applied at different rates i.e. 100, 75, 50 and 25% (of recommended rate) of P with alone polymer-coated and uncoated DAP fertilizer as control. Application of HPCDAP at 100% rate of P increased plant height (17%), biological yield (38%), grain yield (45%), agronomic efficiency (60%) and recovery efficiency (66%) of wheat crop in comparison to uncoated DAP on normal soil, while in saline soil these increases were as plant height (23%), biological yield (54%), grain yield (63%), agronomic efficiency (76%) and recovery efficiency (76%) in pot experiment, while this treatment under field conditions increased plant height (20%), grains yield (19%), number of tillers m-2 (20%), straw yield (17%), biological yield (16%), total N uptake (26%), total P uptake (32%) and total K uptake (22%) in normal soil whereas plant height (27%), grains yield (26%), straw yield (22%), number of tillers m-2 (27%), biological yield (23%), total N uptake (26%), total P uptake (47%) and total K uptake (25%) in saline soil. The treatment where 75% rate of HPCDAP was applied showed non-significant results when compared with 100% rate of HPCDAP in saline soil. A highly positive relationship between polymer enriched with hormones coated DAP and crop response revealed promising results on growth, yield, and P use efficiency of wheat in both saline stressed and non-stressed soil. These results recommend this a novel approach to get optimum cereal yield under salt stress conditions.