Abstract: A field experiment was conducted to promote castor plantation in the irrigated oasis area of northwest China.At each growth stage,the dry matter and nitrogen (N),phosphorus (P),potassium (K) accumulation of stem,leaf and ear were determined and the effective accumulated temperature was recorded.The results indicated that all the dry matter accumulation rates of stem,leaf and ear tended to present a change rule of“slow-fast-slow”,but the peaks of the dry matter accumulation rate of different organs were different,with vegetative organs at flowering stage and ear at fruiting stage.Starting from fruiting stage,the assigning rate of the net dry matter accumulation in ear was larger than that in vegetative organs gradually,and it reached the peak of more than 80% at filling stage.The nitrogen accumulation of castor plants mainly occurred before filling stage,but the phosphorus accumulation of castor was still high at filling stage.And at this stage,plenty of the phosphorus and potassium in leaf and stem was transferred to ear.In addition,from budding to mature,both of main ear and ear at level 1 needed 58 days,but main ear needed effective accumulated temperature of 924 ℃ and level 1 ear needed 888 ℃.It followed that growth and fertilizer regularity of castor showed a consistent trend and both of their peaks were at flowering and fruiting stage,so at this stage the management of fertilizer should be strengthened,besides,at middle and later growth stages phosphate and potash fertilizer topdressing should also be noticed.

Key words: castor, growth stage, effective accumulated temperature, dry matter, net accumulation, assigning rate, arid area