Combined Effects of Elevated Manganese and Zinc Levels on Germination, Chlorophyll Development, Foliar Nitrogen and Carbon Sequestration in Sorghum bicolor seedlings

Abstract

Sorghum is a major staple crop in many parts of semi-arid tropics, but soil nutrient deficiencies and pollution are limiting its performance. The study was carried out to determine the combined effects of elevated levels of manganese and zinc in the soil on the germination and performance of Sorghum bicolor seedlings at the early stage of growth. A 9×3 complete block design (CBD) experiment consisting of 10 mg/kg and 100 mg/kg manganese (Mn) levels each with sub-levels of zinc (Zn) at 0 mg/kg, 10 mg/kg, 20 mg/kg and 40 mg/kg were set-up in three replicates alongside the uncontaminated control. Sorghum bicolor L. Moench were sown in the treatments after two weeks of spiking. The set-up was observed for germination (as from 1 day after sowing - DAS), cchlorophyll index (at 7 DAS and 14 DAS), leaf nitrogen (at 14 DAS), biomass accumulation of seedlings (at 14 DAS). The results showed that germination occurred in all the treatments at 3 DAS and the combined low (10 mg/kg) Mn with low (10 mg/kg) Zn treatment achieved the highest germination rate (100%) while high (100 mg/kg) Mn without Zn had the least (26.67%). High Mn combined with high Zn improved chlorophyll index and leaf N. Contrarily, increasing levels of Mn had no significant impact on biomass accumulation/carbon sequestration. The study concluded that Mn and Zn spiking differently impacted on the performance indices of sorghum. The combined low levels of Mn and Zn improved germination while increasing levels of both metals enhanced chlorophyll and foliar N concentration in sorghum.