Studying Maize Growth Indices in Different water Stress Conditions and the use of Humic Acid
Parisa sharifi

Department of Agronomy, Faculty of Agriculture, Urmia University, Iran.

Abstract: An experiment was conducted in split plots in a completely randomized block design with three replications to evaluate the impact of drought stress on physiological indices of maize growth and the effect of humic acid fertilizer on alleviating drought stress. The main factor included three irrigation levels of 100%, 75%, and 50% and sub-factor was the use and non-use of humic acid. The results showed that in all different levels of irrigation and humic acid treatments, the index of leaf area index (LAI), crop growth rate (CGR) and dry matter accumulation are sigmoid. The highest LAI was (4.5) and biological yield was (15.5 ha) in full irrigation treatment with humic acid, and minimum LAI was (3) with biological yield (8.8 tons per hectare) in 50% irrigation treatment and non-use of humic acid. The results showed that LAI and receiving light were the most important factor affecting the growth indices. Moreover, the highest and lowest CGR CGR, relative growth rate (RGR) RGR and net absorption rate (NAR) were related to full irrigation + consumption of humic acid and 50% irrigation and non-use of humic acid respectively. Overall, the results showed that in without stress treatment (irrigation 100%), the use of humic acid compared to non-use increased RGR, CGR, NAR and LAI at 1.3%, 21%, 8% and 12.5% respectively. This is while in water stress (irrigation 50%), humic acid consumption increased these indices 7%, 25%, 14% and 30% respectively representing a reduction drought stress by humic acid. In general, it could be argued that the use of humic acid, due to adjusting the drought, could have a positive role in water stress to reduce the use of chemical fertilizers, reducing environmental pollution, and to mitigate drought stress, and as is suggested a stable source of supplying nutrients in drought conditions for maize.

Keywords: The effect of humic acid fertilizer; maize growth; irrigation level

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