Abstract: Non-point pollution to the environment originated from agricultural activities has increasingly drawn concern globally. Though numerous studies have been aimed at this subject, those involving effect of cropping patterns on nutrient loss are rare. The influences of rain intensity and cropping patterns on N and P losses were studied using a completed randomized block experiment adopting artificial rains onto the simulated runoff blocks. Results showed that the amounts of both surface and total runoff were coincided with rain intensity, while the underground runoff was negatively correlated with rain intensity. High rain intensity tended to undermine penetration of rain water into soil and thus reduced soil moisture. At same rain intensity, flat cultivation produced maximal surface runoff and soil erosion. Contour cultivation, however, seemed ideal in controlling soil erosion and surface runoff at small to medium rain intensity, but this effect was weakened at heavy rain intensity. Furthermore, it tended to elevate underground runoff that was responsible for main loss of N. It was observed that P was predominantly lost to sediment and highly correlated with rain intensity. At small to medium rain intensity, N was carried away from the plot by runoff, especially by underground runoff. Thus, it is very crucial to make underground runoff under control in order to control N loss to environment. As for P, any methods to effectively stop soil erosion are the solutions. Under the conditions of this experiment, about 1% of fertilizer N (available N) was leached out of the soil and became the non-point pollutant to environment; while for P, its loss to environment was very minor, only accounting for less than 0.3‰ to 1‰ of fertilizer P applied.

Key words: Rain intensity, cultivation method, purple soil, nutrient losing, soil erosion