Abstract: Field experiments were carried out on upland rice mulched with semi decomposed rice straws,horsebean stems,plastic film,paper film or raw rice straws to study their respective effect on N absorption of the crop.In the experiment comparison was also made between paddy rice and upland rice in yield,yield components and utilization efficiency of irrigation water.It was found that the upland rice was higher than the paddy rice in N content in almost every organ.In the upland rice N absorption and accumulation occurred mainly after the jointing stage,whereas in paddy rice the absorption of large amount of N started right after transplantation and then little N was absorbed after the filling stage.The highest yield of upland rice was found in the treatment with semi decomposed rice straws as mulching,reaching 8 415 kg/hm ²,but its water consumption was only 7 14% of that of the paddy rice,about 12 times as high in water use efficiency.

Key words: biological effect, mulch, nitrogen, rice, upland paddy