Effect Of Nitrogen Application On Coupling Leaching Of Nitrate Nitrogen And Base Cations In Variable Charge Soil

Nitrogen,as an essential plant nutrient,is listed before P and K and as one of the most important input of agricultural production,it plays an enormous role in the increasing of both production and income.However,since1970s,the amount of fertilizer consumption in our country is increasing gradually by year and the amount of nitrogen fertilizer takes up about60%of fertilizer consumption in our country and the nitrogen fertilizer consumption in our country takes up more than35%of the whole world.The excessive application of nitrogen fertilizer can not only affect crop yield, reduce quality of agricultural products, aggravate pests and do harm to the environment but also can cause permanent damage to the soil such as soil compaction and soil acidification. As a result, it is of great value to study the coupling leaching characteristics of nitrate ion and base cations in latosol and yellow soil, to prove the influence on leaching characteristics of ammonium ion, nitrate ion and base cations caused by the sorts and amount of nitrogen fertilizer and to predict the characteristics of nitrate ion and base cations. In this paper,yellow soil and latosol were taken as subjects which were collected in Xiannv Mountain of Wulong in Chongqing and Guanlan Lake of Haikou in Hainan province respectively. In the method of siol column indoor and intermittent leaching experiment, the leaching characteristics of soil anion and base cations were observed and analysed under different sorts and amount of nitrogen fertilizer-urea N0, N1, N2, N3, N4; ammonium nitrate N0, N1, N2, N3, N4;ammonia sulfate N0, N1, N2, N3, N4-to discover the the coupling leaching characteristics of soil anion and base cations and reveal the intrinsic mechanism of soil acidification resulted from the application of nitrogen fertilizer from a new aspect, and then to improve the nitrogen use efficiency and control the process of soil acidification. The main conclusions of this paper are as follows:1.The influence of different sorts and amount of nitrogen application on N leaching characteristicsNo matter in latosol or yellow soil,the leaching of nitrate nitrogen is much higher than that of ammonium nitrogen and the leaching of yellow soil is higher than that of latosol. The leaching characteristics of nitrate nitrogen in yellow soil and latosol are respectively in an order of ammonia sulfate> ammonium nitrate> urea> N0, ammonium nitrate> urea> ammonia sulfate> N0; while the order of ammonium nitrogen is ammonia sulfate> ammonium nitrate> urea> N0, ammonia sulfate> urea> ammonium nitrate> N0, respectively. The relationship between the accumulated leaching of NO3--N in latosol (y) and the application of urea, ammonium nitrate and ammonia sulfate(x) can be depicted by the following linear equation respectively:y=1.1064x+3190.8(R2=0.9395), y=1.2324x+3673(R2=0.9209), y=0.4972x+5092(R2=0.9977). The average leachings of NH4+in urea, ammonium nitrate and ammonia sulfate treatment in latosol all show the trend that N4>N3>N2>N1>N0. The NH4+-N leaching rate of urea and ammonium nitrate is0.42%and0.30%respectively,while that of ammonia sulfate shows the tendency that with the increasing amount of fertilizer, the amplification of NH4+is decreasing gradually and when the amount is over N3, the amplification becoming negative.The relationship between the accumulated leaching of NO3--N in yellow soil (y) and the application of urea, ammonium nitrate and ammonia sulfate(x) can be depicted by the following linear equation respectively:y=2.4756x+5560.9(R2=0.9887), y=2.1125x+6470.3(R2=0.9909), y=0.7207x+5320.1(R2=0.9854). In yellow soil, the average leaching of NH4+of urea treatment, shows the trend that N3> N4> N2> N1> NO0for the ammonium nitrate treatment, the average leaching concentration of NH4+of N1, N2, N3, N4is respectively1.11,1.41,2.74and3.51times of NO; and the ammonia sulfate treatment shows that there is no significant differences among N3, N4and N2, but the three are all obviously higher than N1and N0, and with the increasing of ammonia sulfate, the concentration of NH4+is gradually increasing and when it over N2, the amplification slows down and even turns into negative.2.The influence of different sorts and amount of nitrogen application on coupling leaching between nitrate ion and base cationsIn latosol, the total leaching of base cations:ammonia sulfate> ammonium nitrate> urea> NO, and the leaching of base cations of all the three fertilizers show that: Ca2+>Mg2+>K+>Na+. In this experiment, the migration rate of base cations increases with the minishing of pH and shows the tendency:ammonia sulfate (26.28%)> ammonium nitrate (13.37%)> urea (11.78%). The migration of Ca2+is in the ascendant location and in the ammonia sulfate treatment, it is26.32%,14.86%higher than that of urea treatment which is only11.46%and12.63%higher than that of ammonium nitrate treatment which is13.69%. In this experiment, the base cations migration rate in N1, N2, N3, N4treatment is respectively19.80%(R2=0.9293),14.32%(R2=0.8696),14.63%(R2=0.8652),17.72%(R2=0.9018). The variation trend of the fitting degree between leaching amount of nitrate nitrogen (x) and base cations Ca2+, Mg2+, K+, Na+in latosol is: N1> N4> N2> N3, N4> N2> N1> N3, N1> N2> N3> N4, N1> N4> N2> N3.Compared with in latosol, the total leaching of base cations in yellow soil takes a larger ratio and has the law that ammonia sulfate> ammonium nitrate> urea> N0. The leaching amount of base cations in urea and ammonium nitrate treatments is in an descending order of Ca2+> Mg2+> K+> Na+, while in ammonia sulfate treatment the order is Ca2+>K+>Mg2+>Na+. In yellow soil, the the fitting degree between leaching amount of nitrate nitrogen and base cations in urea treatment is in an order of Mg2+(R2=0.9548)> Ca2+(R2=0.9195)> K+(R2=0.6897) and the fitting effect of Na+is poor; the fitting degree between leaching amount of nitrate nitrogen and base cations in ammonium nitrate and ammonia sulfate treatment is in an order of Ca2+>K+>Mg2+>Na+. The migration amount of base cations increases with the increasing of nitrate nitrogen leaching amount and in the urea treatment the migration rate of base cations is21.49%,9.71%higher than in latosol urea treatment, which is11.78%; while in ammonium nitrate treatment, the migration amount of base cations is21.56%,0.07%higher than21.49%. The coupling migration degree of Ca2+and nitrate nitrogen is high and the migration rate of Ca2+in urea treatment is20.49%, in ammonium nitrate is20.25%,0.24%lower than that in urea treatment. The migration rate of total base cations in yellow soil of N1, N2, N3, N4is respectively22.67%(R2=0.9145),24.52%(R2=0.9163),20.56%(R2=0.9094),22.90%(R2=0.8680). In treatment of N1, N2, N4, the imitative effect between accumulated leaching of nitrate nitrogen (x) and migration of base cations (y) is in an order of Ca2+> Mg2+> K+> Na+, while in N3, the order is Ca2+> Mg2+> Na+> K+.3.The influence of different sorts and amount of nitrogen application on soil acidificationThe total amount of base cationsof latosol and yellow soil is in an order of urea> ammonia sulfate> ammonium nitrate. For the latosol, base saturation, surface charge density, Surface electric field strength and specific surface area is respectively in an order of urea> ammonia sulfate> ammonium nitrate, ammonia sulfate> ammonium nitrate>urea, urea> ammonia sulfate> ammonium nitrate, ammonium nitrate> ammonia sulfate>urea. For the yellow soil, base saturation, surface charge density, surface electric field strength and specific surface area is respectively in an order of urea> ammonium nitrate> ammonia sulfate, urea> ammonium nitrate> ammonia sulfate, ammonia sulfate>ammonium nitrate> urea, urea> ammonium nitrate> ammonia sulfate. The theory total surface charge of latosol has the tendency of urea> ammonium nitrate> ammonia sulfate and the SCNt is between93.91and112.23mmol/Kg; while in yellow soil, the tendency is ammonia sulfate>ammonium nitrate> urea and the lowest theory total surface charge of NO is30.49mmol/Kg and the SCNt is between30.49-80.35mmol/Kg. For latosol, the surface charge density in urea, ammonia sulfate and ammonium nitrate treatment is respectively in an order of N1> N2> N3> N4, N1> N4> N2> N3, N4>N2>N1=N3;while for yellow soil, the order is respectively N3> N4> N2> N1, N4> N1> N3> N2, N1>N2>N4>N3.