The estimated input and output of nitrogen illustrated that Ncycling was not balance in cotton field ecosystem.The output of nitrogen was more than the input.The balance values of incomeloss of nitrogen (Bk) were -98,-106,-135 and -162,in the low yield powder field(LYPF),in the middle(MYPF),in the high(HYPF)and in the euper high(SHYPF),respectively.The apparent balance of input/output(B1)were 09113、09435、09429 and 09458 in LYPF,MYPF,HYPF and SHYPF,respectively.The Nexported cotton products ...