ESTIMATION OF TEMPORAL VARIATION RESILIENCE IN COTTON VARIETIES USING STATISTICAL MODELS
Being the queen of fibers, cotton (Gossypium hirsutum L. enjoys itself a predominant position amongst all other cash crops. It holds a lion's share in the foreign exchange (55% of Pakistan and it production accounts for 1.5% in GDP and 7.1% in agriculture value addition (GOP, 2015) Invention of Bt. (Bacillus thuringiensis) genotypes has caused a hesitation among farmers whether to sow it or not owing to the controversial debates regarding it's sowing windows and some other complications. It is a well known fact that crop growth, and development are weather dependent and it is considered as the most limiting factor in crop production (Hoogenboom, 2000; Yucel and Gormus, 2002) Among environmental factors affect cotton growth, developmental rate and yield, temperature plays a crucial role as it determines the initiation and ending period of phenological stages during crop growing cycle (Luo, 2014) Cotton crop requires specific thermal time for the completion of each phenophase (Bange and Milroy, 2004) but critical phenophases are detrimentally affected by extremely high and cold temperature stresses. Although cotton is a perennial and morphologically indeterminate crop but it is phot period sensitive (Bange et al. 2008) Degree day's accretion above an effective threshold temperature is considered as a good estimate for temperature impact on growth and development. Each phenological stage of varieties requires a specific thermal time for its initiation and completion but it is strongly influenced by sowing time (Sikder, 2009) Sowing time and duration of growth cycle are determined by the Pak. J. Agri. Sci. Vol. 53(4) xxx xxx; 2016 ISSN (Print) 0552 9034, ISSN (Online) 2076 0906 DOI: 10.21162/PAKJAS/16.4549 http:/www.pakjas.com.pk