Enhanced Wheat Yield: Fulvic Acid Application's Impact on Yield Factors under Heat Stress

Abstract

Terminal thermal stress, occurring under various climatic conditions, significantly 
reduces wheat yield by disrupting fertilization and grain filling processes. Biostimulants offer a 
potential solution to mitigate the impact of terminal heat stress on wheat crops. This research aims 
to alleviate the effect of heat stress on wheat through the application of fulvic acid. The wheat crop 
was subjected to elevated temperature stress during the booting and grain initiation stages under 
field conditions, with heat stress at staggered intervals in the main plot. Fulvic acid was applied at 
different concentrations (water spray, 1.25 mg L-1, 2.50 mg L-1, and 3.75 mg L-1) in field and heat 
stress conditions upon booting (H1) and grain initiation (H2) stage. Results revealed that heat stress 
H1 and H2 stages significantly decreased the spike length (22.59% & 21.45%), spikelets per spike 
(14.35% & 6.66%), grains per spike (27.9% & 20.23%), grain weight per spike (40.24% & 
32.54%), test weight (17.84% and 15.69%), biological (41.19% & 32.61%) and straw yield 
(31.20% & 19.16%), and harvest index (9.8% & 8.31%) as compared to control (H0). The impact 
was more pronounced during the booting stage compared to the grain filling stage. Application of 
fulvic acid at concentrations of 3.75 mg L-1 during heat stress at the booting stage and 2.50 mg L-1 
upon heat stress at grain initiating stages substantially enhanced the recorded parameters compared 
to the foliar application of water and 1.25 mg L-1 fulvic acid. These findings revealed that foliar 
application of fulvic acid promotes thermotolerance in wheat, positively influencing yield and 
yield-contributing factors during heat stress.