Study Of The Loss Characteristics Of Nitrogen And Phosphorus From The Fields In The Riverhead Protection Region Of Huangpu Upriver

In this paper the loss pattern of nitrogen and phosphorus from the fields in the riverhead protect region of Huangpu upriver are studied based on the planting patterns, high-density water distributing and other related local status by collecting and analyzing the content of NO₃-N, NH₄-N, total nitrogen and soluble total phosphorus of the water samples. Effecting factors such as raining process, fertilization, crop types are all considered. Determining and evaluating methods of the loss pattem of nitrogen and phosphorus from field are also discussed in the paper.It is showed that multi-points group samples in regional area can be used to reveal the effect of crop types and its growing seasons on the nitrogen and phosphorus loss. The loss potential of nitrogen and phosphorus can be quantified by this method when it's studied combining with runoff and infiltration experiments.The loss rates of total nitrogen and total soluble phosphorus from the vegetable fields are respectively 7.32 and 0.27. They are 15 and 2 times of that from the rice-wheat rotation fields which are 0.442 and 0.12 respectively. And the concentrations of total nitrogen and total soluble phosphorus in the top-water of the vegetable fields are also higher than that of crop fields. The infiltration experiment shows that the infiltrating loss rates of nitrogen and the soluble phosphorus are less than 2% and 0.3% respectively.The study also shows that the losses of nitrogen and the soluble phosphorus are related to the growing seasons. In high-rainfall seasons the concentrations of nitrogen and the soluble phosphorus are much higher in both the top-water of the fields and river water compared with low-rainfall seasons, which is 2-5 times and 2 times respectively for the soluble phosphorus. Same conclusion on the losses of nitrogen and phosphorus can be gained with the runoff experiment while it is maybe affected by fertilization.The research gets the runoff and infiltrating loss rate from fields of riverhead protect region of Huangpu upriver. And nitrate is the main loss form of nitrogen. The study also shows that the rtmoff loss rate of single crop is 10.15-49.39%, which is 15.1%, 30.6% and 22.4% in the Xicen, Zhujiajiao and Maqiao respectively. And the runoff loss rate of wheat is higher than that of rice. The infiltration rates of Chinese flat cabbage, cabbage and barley are 55.1%, 54.6% and 56.6% respectively which there are not great difference among them. This indicates that about half of rainfall loss from infiltrating to groundwater. And the nitrogen and phosphorus in this part of water are one of the leading causes to groundwater pollution. The loss rates of nitrate in the runoff and infiltration experiments are 24～53% and 23～70.5% respectively, which is all higher than the loss of NH₄-N.