| Nitrogen and phosphorus balance characteristics in typical small watershed in Jianshan River in Chengjiang basin sloping of agro-ecosystem in sloping filed were analyzed by sentinel surveillance methods to micro-plots as the research object. A large number of basic data were collected through the extensive on-site investigation, referring to documents, and interrelated conclusions were received through staying at small watershed for long time, laboratory analysis and software processing. The results showed that:(1) Rainfall was the main reason and propulsion of nitrogen and phosphorus loss entering water. The time characteristics of nitrogen and phosphorus losses were determined by time distribution of rainfall in small water shed. The annual rainfall was 627.4mm during the year 2009 in small watersheds in Jianshan River, Chengjiang, and the rainfall was about 40% lower than the average annual rainfall. The rainfall more than 10 mm accounted for 71.48% of the whole rainfall, and this rainfall was the main type. In different rainfall, runoff and rainfall had the same tendency, and they showed a good linear relationship, the correlation coefficient reached 0.8641 (P <0.05) between rainfall and runoff. While rainfall intensity and runoff had certain linear relationship in the certain rainfall. Soil erosion and rainfall did not show a good correlation, while rainfall intensity had a positive relationship with sediment amounts. Runoff and soil erosion reached extremely remarkable level (P <0.01) under the influence of rainfall characteristics.(2) Nitrogen and phosphorus concentrations of surface runoff decreased as a whole with time. The fertilizer was 0 kg/hm2,292.5 kg/hm2,678.75 kg/hm2,1065 kg/hm2,1451.25 kg/hm2,1837.5 kg/hm2 from 1 to 6 treatment. Under the same amount of rain, nitrogen and phosphorus concentrations increased with fertilizer, and they registered as: 1 <2 <3 <4 <5 <6. Under the different amount of rain, the concentration of TN, NH4+-N, NO3--N reached 5.57mg/L, 4.36mg/L, 1.30mg/L; the concentration of TP, PO43--P reached 0.68 mg / L, 0.48 mg / L. Nitrogen mainly lose with runoff, and accounted for 64.86% of losses amounts. While phosphorus mainly loses with sediment and phosphorus losses was more than nitrogen losses. PO43--P accounted for 30.43%-87.05% of phosphorus runoff.(3) The content of TN in soil with fertilizer and no fertilizer reached remarkable level, the best period to control soil nitrogen loss was about one month after topdressing. In the period of plants harvest, nitrogen of surface soil of 4, 5, 6 treatments was brought down by high-speed, and then steady-going, and was 24.24%-47.83% on July 7th. Phosphate migration in soil was weak; TP in soil had a great relationship with background value in soil. TP in different soil level decreased slightly with time. Available phosphorus in soil migrates easily with water, and available phosphorus had not a great relationship with background value in soil.(4) Dry yield with fertilization and no fertilization reached remarkable level, dry yield with fertilization was 2.71-6.26 times than dry yield with no fertilization. Flue-cured tobacco yield was biggest when nitrogen fertilization was about 127.80 kg/hm2, and phosphorus was about 63.90 kg/hm2 in this trial. Fresh yield was 1.32-6.5 times than others, dry yield was 1.25-6.26 times than others. Flue-cured tobacco N, P absorption had a certain range. The 4th treatment N absorption was 1.83-19.26 times than others; P absorption was 5.33-83.67 times. Within a certain range, N, P agricultural recovery, plants accumulation increased with fertilizer increasing.(5) Different organs nitrogen distribution amount of flue-cured tobacco at maturity stages registered as: leaf>stem>root. Leaf nutrient absorption was lower when fertilization was low. Flue-cured tobacco stem nutrient absorption was 10%-60% higher than leaf and root. NO3--N of different treatments were insignificantly different (P<0.05) except the 3rd and 6th treatments. NO3--N contents were 352.77mg/kg-487.25mg/kg,and they registered as: stem>leaf>root. While phosphorus absorption were different, different treatments registered as: stem> root >leaf.(6) Rainfall and fertilizer mainly caused the difference of nitrogen and phosphorus concentrations, and nitrogen and phosphorus exports reached extremely remarkable level. Nitrogen, phosphorus output and input achieved a balanced relationship under 6 different fertilization conditions. Nitrogen absorption accounted for 81.08% decreased into 15.97%, phosphorus absorption accounted for 7.76% decreased into 0.51% with the increase of fertilizer, when nitrogen fertilizer was higher than 127.80 kg/hm2, phosphorus higher than 63.90 kg/hm2.While losses amounts increased obviously. The losses were significantly affected the ecological balance and environment. The residual amounts in soil increased slightly, long-term fertilization will lead to accumulation of soil fertilizer. The residual amounts would provide a sufficient source with runoff losses. |
PDF Full Text Request