Effects of rainfall intensity on soil nitrogen and phosphorus leaching characteristics in different planting patterns
In order to explore the effects of different planting patterns and rainfall intensities on the rate of N and P leaching as well as soil N and P content in Morella rubra L.forests,an indoor column experiment was performed to simulate the effects of different understory planting patterns(Medicago sativa cv.WL525HQ monocropping,Dactylis glomerata cv.Amba monocropping and mixed cropping).The effects of heavy rainfall on N and P loss through leaching was simulated in soil at 20,40,and 60 cm.The results showed that the differences in planting patterns had a significant effect on the fluxes of N loss from leaching,and considerable N loss occurred under M.sativa monocropping.The concentrations of total nitrogen(TN)and dissolved nitrogen(DN)from leaching at 60 cm increased by 27%and 29%compared with that from pore water at 40 cm.However,the D.glomerata monocropping effectively reduced the concentrations of TN and DN from leaching in pore water between 0-40 cm and 60 cm,and both the concentrations of TN and DN in the leachate were reduced by approximately 60%at 60 cm compared with that at 40 cm.The flux of P losses was significantly affected by planting pattern and rainfall intensity in the M.sativa-D.glomerata mixed cropping and was reduced 70%and 60%compared with the values obtained from the M.sativa monocropping and D.glomerata monocropping,respectively.The correlation analyses showed that TN,DN and TP contents in leachate were correlated with soil available nitrogen,and that the grassing pattern had a greater effect on quick-acting nitrogen as rainfall intensity increased.The results showed that AN content was highest(32.6 mg·kg-1)in the at 0-40 cm soil layer under M.sativa-D.glomerata mixed cropping under heavy rainfall,and there was no obvious difference among the three planting patterns at 60 cm.In conclusion,under heavy rainfall,D.glomerata monocropping had a significant effect on reducing N loss fluxes.In the mixed cropping pattern,the increase in the average diameter and total root volume of D.glomerata under heavy rainfall may be the reason for improved retention of soil AN at 20-40 cm and impeded migration of AN constituents from the topsoil to deeper depths.Based on these results,the M.sativa-D.glomerata mixed cropping pattern was determined to be an effective measure in reducing the N and P loss fluxes in conditions of extreme rainfall intensity.
planting patternrainfall intensityleachingnitrogen and phosphorus loss
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