Simulating soil nitrogen dynamics at fields and landscape scales: Experiences from China and Canadian Farmland

Nitrogen use efficiency in field crop research can be assessed in different approaches. This presentation introduced soil nitrogen (N) balance and N leaching simulation study in both field and farmland scales. Field scale soil N dynamics was carried out using the Decision Support System for Agrotechnology Transfer (DSSAT) v4.6 model with CENTURY-based soil model. Soil N leaching estimations at landscape were carried out using a self-developed Canadian Agriculture Nitrogen Budget (CANB) v4.0 model. Three long-term field experiments were selected to illustrate soil N leaching studies. (1) A long-term continuous maize experiment from 1990-2007 in Gongzhuling, Northeast China with N application rates of (i) zero N (N0), (ii) 165 kg N ha-1 form chemical fertilizer (N165) and (iii) 110 kg N ha-1 from chemical fertilizer plus 55 kg N ha-1 from farmyard manure (N165M). (2) A 50- year long-term continuous maize experiment at Southwestern Ontario, Canada with two treatments; (i) continuous corn with fertilization (CC-F) and (ii) continuous corn without fertilization (CC-NF) from 1959-2007. (3) A spring wheat long-term experiment with continuous wheat with N and P fertilizers and Wheat-Fallow rotation experiment with N and P fertilizers treatments at South Saskatchewan, Canada from 1967-2005. Nitrogen leaching study at Canadian landscape scale was carried out from 1981-2011 at Soil Landscape of Canada 1:1M scale. Residual Soil Nitrogen (RSN) at harvest was calculated based on differences of total N input minus N outputs based on an annual RSN budget model. Various agricultural production (i.e., soil, crops, areas, yields and livestock management) and fertilizer management database were used as input to calculate the RSN. Daily weather data was used to calculate the non-growing season (NGS) and growing season (GS) drainages at each location. Then, N leaching loss was estimated in both NGS and GS seasons. The results were scaled up to various eco-regional, province and Canada scales. The main results of RSN and N leaching at temporal and special scales were illustrated.