| The relationship of amount and distribution of cotton bolls with N rates during growth period was studied through field experiments. The main results were as follows: number of available cotton bolls were strongly correlated with N rates, and shedding rates of buds and bolls were negatively correlated with N rates; abundant nitrogen nutrition were the necessary condition to increase available bolls and decrease shedding rate; applying nitrogen fertilizer prolonged the duration of cotton bolling increase and delayed the increasing trend of shedding rates; applying nitrogen fertilizer increased number of available bolls on different fruit branches, especially enhancing the proportion of cotton bolls on the middle and lower branches, and reducing shedding rates of bolls on the middle and lower branches. |