Abstract: By using bidirectional sampling method with soil drill, the effects of different amounts of drip irrigation (2618, 2947, 3600 and 4265 m3·hm-2) under mulching on the root distribution, aboveground growth, and yield of cotton was studied in field. The results indicated that irrigation amount affected the root and shoot growth significantly. In all irrigation treatments, cotton root was m ainly distributed in mulched area, occupying 6065%〖KG-*2〗-〖KG-*7〗7345% o f total root biomass, while only 3935%〖KG-*2〗-〖KG-*7〗2655% was distribut ed in bare area. Water stress increased rooting depth, root biomass, and the ext ent of lateral rooting. Significant differences were observed in the biological characteristics and the biomass accumulation and allocation of cotton plant amon g different irrigation treatments. Over-irrigation (4265 m3·hm-2) incr eased plant height, width of inverse fourth leaf, and amounts of branch and bud, and thus, accelerated biomass accumulation rate. Over-irrigation also increase d the root/shoot ratio and the proportion of biomass allocated to vegetative org ans, but increased the fruit abscission rate and therefore reduced the economic yield. It was suggested that both excessive soil moisture content and water stre ss could affect the biomass accumulation and allocation in different cotton orga ns and at various life stages. Under the conditions of our experiment, 3600 m3 ·hm-2 was the optimal irrigation amount.

Key words: energy flow, compound agriculture-fruit farming system, output/input ratio.