Study On N & P Pollution Flux From Agricultural Non-point Sources Of The Main Paddy Soils In Tai-Lake Region

The objective of this paper was to study the soil properties, to study the nitrogen (N) &phosphorus (P) transferred rules and nutrient losses brought by the surface water; to studythe effect of optimum fertilization and buffer-strip; and to study the nutrient leakage ofpaddy fields in three main kinds of paddy soils (Bai soil, Huangni soil and Wushan soil) inTai Lake region. The results should provide basic parameters and scientific guides toenvironmental protection and macroscopical decision-making of agriculture.The results were as follows:1. Through the Lysimeter experiment, the rules of N&P transferred in soil leachate ofHuangni soil type paddy fields were found. The concentrations of N&P of leachate withthe quantity of fertilizer applied were presented the just linear related, which wassignificantly difference among different levels fertilized at the bringing of fertilization. Theconcentration of NO₃^--N in the soil profile displayed a increasing trend with the depth,which maximum was at the bottom. N was leached away mainly in the form of NO₃^--N inrice-growing season, which was accounted for 1.04%～1.93 % of total fertilizer applied;The NH₄⁺-N centralized in the surface layer of paddy field soil was easily adsorbed by thesoil colloid, and the quantity of NH₄⁺-N leached was rarely, which influence to theenvironment was small. P was fixed easily after fertilization with the very small movingability, prolonged the release time and the transference if applied together with pig manure.2. The changing rule of the nutrient concentration in the surface water was found,through the Lysimeter field experiment and inside analysis. The concentration of NH₄⁺-N,NO₃^--N of surface water with the quantity of fertilizer applied were presented the just linearrelated; The emergence time of NO₃^--N maximum was behind the NH₄⁺-N, so the rate ofNH₄⁺-N (NO₃^--N) /T-N of the surface water could reflect the relative level betweentransform and the ability of nutrient loss; The maximum of The rate of NH₄⁺-N/T-Ndescended with the time in the late which maximum was 97.79% in the after fertilizationtwo days, and the trend of NO₃^--N /T-N's was contrary, which expressed that NH4+-Nshould be was the basilica monitor object in the initial stages of fertilization and NO₃^--Nwas the basilica monitor object in the later of fertilization.3. The loss of N&P in paddy-field stream was studied in the stream field of ChangshuAgro-Ecological Experiment Station. The study indicated that besides the quantity andperiod of fertilization, the main factor effecting loss of N&P in paddy-field stream wasquantity and frequency of rainfall. In Changshu experimental field in rice-growing season,stream loss flux of NH₄⁺-N was 0.223 kg hm^-2, and NO₃^--N's was 0.145 kg hm^-2, whichindicated that stream loss flux of NH₄⁺-N was larger than the one of NO₃^--N, and theNH₄⁺-N was the main form of N stream loss, so monitoring of NH₄⁺-N loss should be emphasized. Employment of phosphor manure increased the potential of phosphor loss.Stream loss flux of DTP in Changshu experimental field was 0.030 kg hm^-2, which waspotential to cause Eutrophication of water body. DTP was an important item of streamnutrient loss monitoring.4. The contrast of influence of different fertilization on rice yield and waterenvironment manifested several facts as follows: 1, rice yield under optimized fertilizationhad little difference with the one under normal fertilization, but N dosage reduced by 22ï¼…,N stream loss reduced by 30％～40ï¼…, and N leakage reduced by 32.3ï¼…; 2, N concentrationof surface water in normal fertilized paddy fields was higher than the one in optimizedfertilized field, N concentration under the two treatment in leachate showed the similar rule,but both were largely less than the one in surface water; 3, P concentration in paddy surfacewater during the rice-growing season exceed the critical value of causing watereutrophication, even up to 15.7 mg.L^-1 after fertilized, which had a risk of pollutingsurround water. So it was a good measure to reduce rate fertilized appropriately and managefertilizers and water well for controlling the agricultural non-point sources.5. Study on controlling the non-point source pollution of paddy-field by buffer strips(BS) indicated facts as follows: 1, Treatment BS differed slightly from TreatmentFertilization in rice yield, the BS would not cause reduction of rice output; 2, N & Pconcentrations in the profile display a declining trend with the depth, suggesting that paddyfield can filter out N and P from irrigation water, to reduce loss of them effectively; 3, BScould significantly reduce N & P loss by intercepting runoff, The total net N interceptedranged between 20.6 and 51.8 kg hm², and the total net P intercepted did between 4.7 and5.1 kg hm^-2. Its role in intercepting N and P in leachate in soil profile was also apparent. BSwas an efficacious measure to reduce the agricultural non-point sources.6. Study on the leakage of three main kinds of paddy fields in Tai lake region usingpaddy-field leakage instrument indicated facts as follows:1, The leachate of paddy-fieldwater declined with time, and performed a distinct negative linear relativity, the maximumof Bai soil paddy field leachate was 3 067 m³ hm^-2, which was higher than the one ofWushan soil's 1 564 m³ hm^-2, while the Huangni soil paddy-field nearly had no leachate; 2,In the same paddy-field of the same kind, the leachate in the middle of a field was muchlarger than those of water-inputting side area and water-outputting side area; 3, Nutrientleakage flux of Bai soil paddy-field was NO₃^--N 8.73 kg hm^-2, NH₄⁺-N 1.57 kg hm^-2, theleakage of NO₃^--N is larger than NH₄⁺-N's, which was the main form of paddy field's Nloss, and leakage flux of DTP was 0.90 kg hm^-2; 4, Nutrient leakage flux of Wushan soilpaddy-field was lower than the one of Bai soil, the NO₃^--N leakage flux of Bai soil was3.32 times of Wushan soil, NH₄⁺-N was 1.38 times and DTP 1.70 times.