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Physio-morphological and agronomic responses of cotton (Gossypium hirsutum L.) to fertilizer management and water stress at different reproductive growth stages
Dissertation Abstract:
The study conducted two experiments (pot experiment at the Crop Science Cluster, UPLB from January to May 2010 and field experiment at the Central Experiment Station (CES), UPLB from October 2010 to February 2011) to investigate the morphological, physiological, and agronomic responses of cotton to water stress and to evaluate the effects of water stress on cotton at reproductive growth stages with different fertilizer management. The cultivar used was CRDI 1 for both experiments. The pot experiment was laid out using a split-split plot in randomized complete block design with three replications, while the field experiment was designed with split plot in randomized complete block design with three replications.
In pot experiment, water stressed plants had significantly reduced plant height, total dry matter (TDM), relative growth rate (RGR), functional leaf area, leaf water potential (LWP), and relative water content (RWC) as compared with control after 20 days. Fertilizer application did not show significant effect on yield and yield components. Among reproductive stages, the flowering stage was very sensitive to water stress and resulted in reduction of TDM, harvest index (HI), RWC, and functional leaf area. The plants where water stress was imposed at flowering stage for 20 days had lower yield. This was associated with lower number of sympodial branch and number of boll per plant resulting from low TDM, functional leaf area, RGR, and HI as compared with control (no stressed) plants. Path coefficient analysis showed that yield components such as number of sympodial branch and number of boll per plant, boll weight, and 1,000 seed weight had positive and significant contribution to yield in both control and water stressed plants (10 days stressed and 20 days stressed).
In the field experiment, water stress at flowering stage reduced TDM, crop growth rate (CGR), leaf area index (LAI), root length (RL), HI, and root shoot ratio as compared with well watered plants (control). Among fertilizer management, FYM + NPK application gave the highest in CGR, net assimilation rate (NAR), and root volume (RV). The lowest value was obtained by FYM alone. No significant difference between FYM + NPK and NPK was recorded in plant height and TDM. Seed cotton yield was lowest in FYM fertilized plants which were subjected to water stress at flowering stage. On the other hand, the highest yield was obtained from well watered plants applied with FYM + NPK. Path coefficient analysis revealed no significant correlation between yield and yield components in control plants. However, in stressed plants, number of boll per plant and number of sympodial branch per plant were positively and highly correlated with seed cotton yield.
