Modeling the Influence of Nitrogen Rate and Plant Density on Seed Yield, Yield Components and Seed Quality of Safflower

Abstract

To study the effect of nitrogen rate and plant density at different levels on yield, yield components and quality traits of safflower (cv. Giza 1) an experiment was conducted as split plot design in randomized complete block design arrangement with three replications, during the successive seasons 2010/11 and 2011/12. The factors consisted of four levels of nitrogen (0, 40, 80 and 120 kg N ha-1) and four different densities (80,000, 100,000, 133,000 and 200,000 plants ha-1). Different statistical analyses such as ANOVA, polynomial regression, correlation, and stepwise multiple linear regression were used. The multiple statistical procedures showed that the main effects of nitrogen rate and plant density levels were significant (P = 0.01) for yield and yield components studied. A rise in nitrogen rate and plant density increased seed and oil yield, whereas plant height, number of branches plant-1, number of heads plant-1, seed yield plant-1 and 1000-seed weight decreased as plant density increased. In general, the highest plant density (200,000 plants ha-1) and the nitrogen level (80 kg ha-1) was the best treatment in this research to attain high safflower seed yield under environmental conditions of Giza Governorate, Egypt. Polynomial models of seed, oil yield and yield components based on the ANOVA were fitted. Polynomial regression analysis indicated that the relationship between the nitrogen amount applied and safflower seed, oil yield and yield components could be defined by using a quadratic function. Also, the results revealed that, yield and yield components were significantly affected by plant density in linear responses. Correlation analysis showed a positive and significant correlation between seed yield ha-1 and each of number of heads plant-1, seed yield plant-1, number of branches plant-1 and 1000-seed weight. Stepwise regression analysis showed that number of heads plant-1 explained 45.57% and along with seed yield plant-1, number of branches plant-1 and 1000-seed weight explained 81.63% of total variations for seed yield (kg ha-1)