Yield is essentially controlled by the genetics of the plant and the environment.
These in turn are further modified by cultural practices. At a more agronomic level, yield may be considered in terms of its major components: Boll number per unit area times the average boll weight.
The growth of the plant and development of bolls depends on the production of dry matter by photosynthesis, and therefore the production of dry matter is the fundamental process of yield. These processes require sunlight, water and adequate plant nutrition. Maximizing these processes through good cultural practices requires careful attention to the factors that we can control, mainly water and plant nutrition. The carbohydrate products of photosynthesis need to be translocated to the developing fruits which in turn need to be protected from pests. Cotton respond to moisture. Water can limit cotton yields. In deserts areas of the world where cotton is produced, irrigation is mandatory. In humid areas, irrigation is critical for maintaining yields during drought.