Combined applications and Multi-Faceted evaluations of humic acid, seaweed, and vermicompost with chemical and organo-mineral fertilizers on corn, part I: chlorophyll concentration

This study investigated the effects of various fertilizers on the leaf chlorophyll content of the Simpatico (FAO300) silage corn variety under field conditions. Different application combinations were tested, including treatments with and without foliar fertilizers. The foliar fertilizers used were seaweed (SW), humic acid (HA), and vermicompost (VC), combined with granular fertilizers DAP, UREA, OMB, and OMT. Granular fertilizers were applied to the soil, while foliar fertilizers were applied at four different stages: the 4-6 leaf period, 11-13 leaf period, 14-16 leaf period, and at corn tassel. Chlorophyll content in plant leaves was measured using a SPAD-502 device during these periods. The highest SPAD chlorophyll ratios were recorded with OMB-OMT (42.583) and DAP-OMT (42.150) treatments, which did not include foliar fertilizers. Conversely, the lowest SPAD chlorophyll ratio, 28.983, was observed in the DAP-UREA treatment. Treatments with foliar fertilizers resulted in an increase in SPAD chlorophyll by 11.3% to 15.7%, with the greatest improvements observed with vermicompost and humic acid, compared to treatments without foliar fertilizers. Additionally, analysis of periodic effects showed that the highest SPAD chlorophyll ratios were found during the third and second measurement periods, while the lowest ratios were observed in the first measurement period. The use of organo-mineral fertilizers and foliar applications of vermicompost and humic acid were found to enhance the leaf chlorophyll content of corn.