Crop stage selection is vital to elicit optimal response of maize to seaweed bio-stimulant application

Burgeoning population demands increased agricultural production; however, the climate change impact being currently experienced necessitates sustainable crop intensification. In this context, Kappaphycus alvarezii seaweed extract has potential to increase the crop productivity in an environmentally friendly way. Since K. alvarezii or rather any seaweed extract contains several beneficial constituents, we hypothesized that not all the stages of crop would respond identically upon its application. A literature survey indicated that there was no concrete rationale behind the frequency and application time of seaweed extract as it arbitrarily varied across the studies. Therefore, a field experiment was designed to evaluate the effect of seaweed extract at select crop growth stages of maize. The application time included ten different combinations chosen among V3, V5, V10, V15, and grain filling stages. The results corroborated our hypothesis, and it was demonstrated that application of a Kappaphycus seaweed-based bio-stimulant at the V10 stage was not effective in significantly influencing productivity. However, in contrast, when applied earlier at V5 or later at the V15 stage, a yield improvement of 13.7 and 11.1% was recorded over their respective controls. We also showed that application of the extract at V5 along with V15 elicited the best yield response (32%) and no further significant gains accrued with higher number of applications. In addition, there was a decline in the benefit-to-cost ratio from 1.7 recorded at V5 + V15 to less than or equal to 1 in other treatments. Consecutive application at V5 and V15 stages also showed a net 20% diminution in the climate change impact category compared to control, and this treatment resulted in savings of 35.7 kg CO 2 -equivalents per tonne of maize grain production compared to that where one application was done at the V10 stage only. Thus, the experimental result highlights the pre-eminence of the crop application stage at which seaweed bio-stimulants can influence yield and profitability and also minimize environmental impacts. However, further trials are needed to validate the findings of this study.