Lysimetry study on the leaching loss of nitrogen from double-rice-cropped ricefield

The effect of N fertilizer application in ricefield on the environmental quality of ground-water was evaluated using large undisturbedmonolith lysimeters.Soil in lysimeters wassilty-clay-loamy paddy soil(Haplaquept)with apH of 6.5,15.4g/kg organic C,1.55g/kg to-tal N,88 mg/kg available N,399 mg/kg A1-abbas-P,67.5 mg/kg exchangeable K,and14.1 cmol/kg CEC.The lysimetry experiment was laid out atHangzhou during the early-rice season(ER,May-Jul)and late-rice season(LR,Jul-Oct)in 1991-1994.Three plot treatments were es-tablished,i.e.,urea plot(UN,applied urea150 kgN/ha per cropping season),ammoniumbicarbonate plot(CN,applied ammonium bi-carbonate 150 kgN/ha per cropping season),and control plot(CK,no N application).Allof the plots also received single superphosphateat 45 kg P/ha and KC1 at 75 kg K/ha.The

Output Characteristics of Non-point Nitrogen and Phosphorus from a Typical Small Watershed in Yimeng Mountainous Area during a Rainstorm

[ Objective] The study aimed to reveal the output characteristics of non-point nitrogen and phosphorus from a typical small watershed in Yimeng mountainous area during a rainstorm. [Method] The dynamic changes of pollutant concentration, precipitation and flow during the rainstorm on August 12, 2010 were monitored at the outlet of Menglianggu watershed. [ Result] During the rainstorm, the generation of runoff was sudden and ephemeral, and the peak of the runoff lagged behind that of rainfall intensity; the concentration of AN and TN increased firstly and then tended to be stable, while NN concentration had no significance change at the beginning of the rainfall, then improved gradually and tended to be stable fi- nally; DOP concentration had no obvious change during the rainstorm, but the concentration of DIP, DP, PP and TP rose firstly and then tended to be stable, and the peak values appeared before the peak of the flow. In addition, the output concentration of TN and TP was far higher than the standard concentration of water eutrophication. [ Conclusion] The study can provide scientific references for the reasonable control of non-point source pollution pollution in Yimeng mountainous area.

Temperature Sensitivity of Nitrogen Dynamics of Agricultural Soils of the United States

Soil temperature controls gaseous nitrogen losses through nitrous oxide (N2O) and ammonia (NH3) fluxes. Eight surface soils from agricultural fields across the United States were incubated at 10°C, 20°C, and 30°C, and N2O and NH3 flux were measured twice a week for 91 and 47 d, respectively. Changes in cumulative N2O and NH3 flux and net N mineralization at three temperatures were fitted to calculate Q10 using the Arrhenius equation. For the majority of soils, Q10 values for the N2O loss ranged between 0.23 and 2.14, except for Blackville, North Carolina (11.4) and Jackson, Tennessee (10.1). For NH3 flux, Q10 values ranged from 0.63 (Frenchville, Maine) to 1.24 (North Bend, Nebraska). Net soil N mineralization-Q10 ranged from 0.96 to 1.00. Distribution of soil organic carbon and total soil N can explain the variability of Q10 for N2O loss. Understanding the Q10 variability of soil N dynamics will help us to predict the N loss.

A DYNAMIC MIXED MODEL WITH NITROGEN LEACHING LOSSES FROM THE PONDED PADDY RICE FIELD UNDER SITUATION OF BURIED PIPE DRAINAGE

In order to study the law of nitrogen leaching losses from the paddy field under the condition of drainage, based on the theories of potential energy and solute transport, a water nitrogen dynamic mixed model by combining the flow net with dynamic method was established. In the computation of buried pipe drainage, the superposition principle was used to simplify the complex solving of the two dimensional problem about water nitrogen transportation in Soil Plant Air Continuous (SPAC) system into several one dimensional problems. The presented method is simple and practical. Some field experiments were carried out to demonstrate the validity of the model.