Asian Research Thesis Index

Abstract

The experiments to improve the drought tolerance in maize (Zea mays L.) hybrids by potassium application were carried out at Postgraduate Agricultural Research Station (PARS), University of Agriculture, Faisalabad, Pakistan. The primary purpose of this study was to know the effect of drought stress continued till harvest and role of potassium to mitigate much adverse effects of drought for growth and yield improvement after optimizing its rate in Faisalabad region. In the first pot experiment screening of eight maize hybrids (FH-810, 32-F- 10, FH-782, 32-B-33, YH-1898, Monsanto-6525, R-2315 and R-3304) against drought was done. Maize hybrids were sown on August 4, 2009 and were uprooted 35 days after sowing. Drought stress (100% FC, 75% FC and 50% FC) was imposed after two weeks of germination till uprooting. The most drought tolerant (32-F-10) and the most sensitive (YH-1898) maize hybrids against drought were evaluated. In the second pot experiment five potassium levels (0, 50, 100, 150 and 200 mg/kg of soil) were optimized under moisture levels 100% and 70% of field capacity maintained after 30% depletion in it while the drought stress treatments were imposed after two weeks of germination. Two hybrids selected from experiment 1 were sown in January 20, 2010 and were uprooted 35 days after sowing and the best fitting potassium level (100 mg/kg of soil) was selected for further study. The third pot experiment was conducted to investigate the influences of potassium on physiological and morphological attributes of maize crop. The two selected maize hybrids from experiment 1 were sown under drought imposed from five critical growth stages (no drought, five leaf stage, ten leaf stage, anthesis and grain formation) till maturity. In this experiment two potassium levels; (0 mg/kg [no potassium] and 100 mg/kg of soil [optimized in experiment no. 2]) were used. Crop was sown for complete life duration on February 28, 2010. Drought was maintained from critical growth stages with moisture of 70% of field capacity after 30% depletion in it. In these three pot experiments CRD (factorial design) with three replications was used. The fourth and fifth experiments were field experiment with; two selected maize hybrids from experiment 1, five critical growth stages to impose drought and two potassium levels. In these experiments moisture application was maintained 70% of field capacity maintained after 30% depletion in it. Two potassium levels; (0 mg/kg) [no potassium] and 100 mg/kg of soil [optimized in experiment no. 2]) were used. RCBD (split-split plot arrangement) replicated thrice, was used. In these experiments the maize hybrids were sown in two years 2010 and 2011 in spring (fourth experiment) and autumn (fifth experiment) seasons. The data regarding morphological, physiological and biochemical parameters were taken by using standard procedures. The data were analysed statistically by using Fisher’s analysis of variance technique and least significant difference test at 5% probability level to compare the treatment means. The analysis of data from first experiment showed that mild and severe drought had deleterious effects on plant height, shoot fresh and dry weight, relative water contents and leaf water potential. However, root fresh and dry weight enhanced under mild drought stress and severed drought decreased the root fresh and dry weight. There was also little effect on photosynthesis under drought stress. On the basis of root dry weight, relative water contentsand leaf water potential, drought stress tolerance and sensitiveness was evaluated. In the second experiment best suited potassium level (100 mg/kg of soil) was optimized where plant root dry weight, leaf water potential and relative water contents was found significantly higher while the further higher levels of potassium were unable to produce significant difference. In the third experiment growth was severely affected by drought when imposed from five leaf stage and drought effect on rest of growth stages has little effect on morphological, physiological and biochemical attributed of maize hybrids. Under the drought stress potassium application enhanced all attributed positively and ultimately enhanced yield. The same study was conducted in field as that of third experiment to investigate the effect of potassium on maize hybrids grown under drought imposed from various growth stages in spring and autumn seasons. Significant effects of potassium were observed on the most of morphological, physiological, biochemical and agronomic parameters. Here in the field severe effect of drought treatment was found when imposed from five leaf stage. However, further research work is required to investigate the potassium efficiency in creating tolerance in maize hybrids under abiotic stresses.

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