Introduction

Drought and water deficit stress always threaten agriculture in hot and dry regions. Considering the progress of science and the existence of advanced devices such as a chlorophyll meter, and investigating the possibility of using the Fv/Fm ratio as a criterion to determine the irrigation time and the effect of drought and nitrogen stress on chlorophyll fluorescence between different varieties of corn, it can be studied and implemented. Conducting such tests in the Baluchistan region, as seen in Bahuklat, has achieved significant results that, to some extent, address the problems caused by water scarcity and drought tensions.

Materials and Methods

This research was conducted to evaluate the effect of water stress and different amounts of nitrogen fertilizer on the chlorophyll fluorescence index of corn cultivars in the 2020-2021 crop year using a factorial split-plot experiment in a randomized complete block design with four replications at Bahuklat research farm. Irrigation treatments at four levels including common irrigation based on region, interruption of irrigation at the flowering stage, the seed filling stage and the flowering and filling stage seed in the main plots and different amounts of nitrogen fertilizer at four levels including treatments of without nitrogen fertilizer, the use of 100, 200 and 300 kg ha-1 of nitrogen; and three corn varieties including of Koosha 201, Fajr 260 and Dehghan 400 were considered in the sub-plots.

Results and Discussion

The research findings indicated that the highest grain yield was achieved with the irrigation control treatment, utilizing 200 kg ha⁻¹ of nitrogen fertilizer, resulting in a yield of 8530.6 kg ha⁻¹. Among the varieties studied, the Dehghan 400 cultivar had the highest grain yield of 6640.11 kg ha⁻¹ and was statistically grouped with the Fajr 260 cultivar. Furthermore, the maximum biological yield was associated with the irrigation control treatment under the nitrogen fertilizer rate of 200 kg ha⁻¹, yielding 20599 kg ha⁻¹. The highest harvest index, recorded at 47.3%, was obtained from the treatment that interruption of irrigation at the flowering stage, and it was also statistically similar to the treatment that interruption of irrigation at the grain filling stage, both using 200 kg ha⁻¹ of nitrogen fertilizer. In terms of chlorophyll fluorescence parameters, the highest Fv/Fm ratio of 0.443 was noted in the treatment that interruption of irrigation at both the flowering and grain filling stages. The treatment using 100 kg ha⁻¹ of nitrogen fertilizer also showed a significant Fv/Fm ratio of 0.415.

It can be said that in the irrigation control treatment, water supply continued according to local practices until the end of the vegetative, flowering, and grain filling stages. As a result, maximum vegetative growth and dry matter yield were observed in this treatment. Additionally, applying nitrogen fertilizer at a rate of 200 kg ha-1 led to increased dry matter production and higher biological yields during the flowering and grain filling stages. The application of 200 kg ha-1 of nitrogen fertilizer enhanced vegetative growth, which in turn boosted photosynthesis, resulting in greater dry matter production and increased biological yield. It is likely that the higher dry weight of the vegetative organs in the Dehghan 400 cultivar is related to its efficient use of environmental factors and its ability to produce dry matter. This cultivar has successfully stored more carbohydrates and reserve substances.

Conclusion

To achieve optimal results in corn cultivation in the Bahuklat region, it is recommended to stop irrigation during the grain filling stage. This advice is based on findings that suggest using 200 kg ha-1 of nitrogen fertilizer and cultivating the Dehghan 400 cultivar will yield the best outcomes.