A multi model evaluation of long-term effects of crop management and cropping systems on nitrogen dynamics in the Canadian semi-arid prairie

Citation

Dutta, B., Grant, B.B., Campbell, C.A., Lemke, R.L., Desjardins, R.L., Smith, W.N. (2017). A multi model evaluation of long-term effects of crop management and cropping systems on nitrogen dynamics in the Canadian semi-arid prairie, 151 136-147. http://dx.doi.org/10.1016/j.agsy.2016.12.003

Plain language summary

It is important that agricultural models can estimate the complete nitrogen balance for the entire crop and soil system. This is needed for assessing the long-term effects of management practices on soil and environmental quality. Using published data collected from a long term study in the Canadian semi-arid prairie, the Canadian DNDC and DayCent models were evaluated for their ability to simulate the long term nitrogen dynamics and budgets as well as nitrogen use efficiencies in a loam/silt loam soil for three distinct spring wheat cropping systems. Both models performed well in predicting the spring wheat grain yields, above-ground plant biomass and nitrogen uptake. The nitrogen balances were also simulated well in the two models; however, the Canada DNDC model results were closer to observations than were those from DayCent for both nitrogen balance and crop nitrogen use efficiency. For both models and the observed data, the nitrogen outputs such as grain nitrogen uptake and nitrogen losses (nitrogen leaching, nitrogen gas emissions) were greater than nitrogen inputs except in the continuous wheat system. Since Canada DNDC performed particularly well across all three cropping systems, the model is a promising tool for analysing nitrogen dynamics and subsequent environmental impacts and benefits.

Abstract

Process-based biogeochemical models such as the DeNitrification-DeComposition (DNDC) and DayCent models can provide reliable estimations of components of the nitrogen (N) cycle but have rarely been evaluated for a more complete N balance. This is important in order to assess the long-term effects of management practices on soil and environmental quality. Using published data collected from a long term study in the Canadian semi-arid prairie, the Canadian DNDC version (DNDC v.CAN) and DayCent models were evaluated for their ability to simulate the long term nitrogen dynamics and budgets as well as nitrogen use efficiencies (NUEs) in a loam/silt loam soil for three distinct spring wheat (Triticum aestivum L.) cropping systems. Both DNDC v.CAN and DayCent models predicted the spring wheat grain yields, above-ground plant biomass and nitrogen uptake well. The predicted NUEs in DNDC v.CAN, calculated using two approaches with respect to grain yield and grain N concentration, indicated good correlations to the observed values with r ≥ 0.70 and low biases and average relative errors. The N balances were also simulated well in the two models, however DayCent showed a higher estimate of the deficit between N inputs and outputs, termed ‘Unaccounted N’, in all three systems compared to DNDC v.CAN. For both model simulations and the observed data, N outputs in the form of grain N uptake and N losses (nitrogen leaching, N gas emissions) were greater than N inputs except in the ContW (NP) system. In general, a multiple linear regression for estimations of NUEs with respect to N balance and N inputs across all three cropping systems showed that, DNDC v.CAN correlated better with the observed data compared to DayCent. Thus, based on model performance in this study, DNDC v.CAN as a process-based model offers promise as a tool for analyzing different cropping systems with varying N rates in terms of N dynamics and subsequent environmental impacts and benefits.

Publication date

2017-02-01