| In this thesis, the effects of different poplar-crop agro-forestry systems on surface runoff,soil erosion and nitrogen and phosphorus losses were studied as well as the nitrogen andphosphorus losses mechanisms though a rainfall experiment with a constant rainfall rate of1.43mm/min. The objective of study was important theoretical significance and application value forinvestigating soil nitrogen and phosphorus loss laws from surface runoff, improving fertilizerutilization efficiency, and reducing eutrophication resulting from agricultural non-point sourcepollution. The main results showed:(1) Compared with wheat mono-cropping system, poplar-crop agro-forestry systems cansignificantly reduce surface runoff (49.6%-74.8%) and soil erosion (53.7%-76.1%). The resultsindicated there existed in negative correlation between stand density and surface runoff and soilerosion in poplar-crop agro-forestry systems.(2) Rainfall intensity was determined to be the main factor influencing the amount ofsurface runoff, total runoff, and sediment in poplar-crop agro-forestry systems. A positivecorrelation existed between surface runoff and soil erosion in poplar-crop agro-forestry systems.(3) Compared with mono-cropping wheat system, poplar-crop agro-forestry systems cansignificantly reduce the loss of total nitrogen (19.9%-62.93%) and total phosphorus(85.4%-96.6%) though surface runoff. The loss of total nitrogen from both wheatmono-cropping system and agro-forestry systems is increased as amounts of fertilizer increased.Compared casing fertilization with applicator fertilization, casing fertilization can decline totalnitrogen(15.29%-32.73%), but no effect on Total Phosphorus.(4) The nitrogen fraction loss from the surface runoff in poplar-crop agro-forestry systems ismainly dissolved nitrogen,Among various modalities of dissolved nitrogen of the surface runoffin poplar-crop agro-forestry systems,the amount of nitrate was the most,but the phosphorusfraction loss from the surface runoff in poplar-crop agro-forestry systems is mainly particulatephosphorus. Poplar-crop agro-forestry systems can increase the loss of dissolved nitrogen andnitrate, while reducing ammonium nitrogen.(5) For wheat mono-cropping system and poplar-crop agro-forestry systems, theconcentration of total nitrogen and dissolved nitrogen decline rapidly, then rise; at the beginning of surface runoff, nitrate is stable, then close to be increased; ammonium nitrogen, totalphosphorus and particulate phosphorus present the same regular pattern, and their concentrationis high in the initial time and then decrease. |
