Factors affecting plant density and cotton yields in Turkmenistan

Cotton has been grown in central Asia for over 2,000 years, and is a major crop in Turkmenistan, where medium staple G. hirsutum is the dominant species, cultivated on 80%of the cotton growing area. Many of the cultivars used in Turkmenistan until the time of independence from Russia were from Uzbekistan. Since independence, the original suite of long staple G. barbadense and medium staple Uzbek cultivars has been considerably changed in Turkmenistan by selection for early maturity and productivity. Cotton yields in Turkmenistan have been declining since independence and were below 2t/ha in 2001 when the TACIS ‘Support to the Cotton Sector Project’ commenced, of which research reported in this thesis was a part. The main factors determining seed cotton yields in this country are quantity of irrigation water applied, nitrogen fertilization, deep ploughing, and plant population. Of these four important factors, plant density is the only one that individual farmers can control, as the others are either state controlled or require equipment held collectively. The aim of the research described in this thesis was to improve cotton production in Turkmenistan through optimising plant population. The use of optimum plant populations in the cotton fields of Turkmenistan has a substantial potential for economic benefit to the farmers of that country. Changing plant populations would require none of the structural changes involved in changing the other important yield factors. Quantity of irrigation water applied is controlled by the state; nitrogen fertilizer is a state controlled input in Turkmenistan and deep ploughing depends on equipment communally held and sometimes unavailable