Abstract. It is still a severe challenge to optimize the field management
practices for a multi-crop system when simultaneously aiming at yield
sustainability and minimum negative impacts on climate as well as
atmosphere and water quality. This site-scale case study was devoted to developing a
biogeochemical process model-based approach as a solution to this challenge.
The best management practices (BMPs) of a three-crop system growing cotton
and winter wheat–summer maize (W–M) in rotation, which is widely adopted in
northern China, were identified. The BMPs referred to the management
alternatives with the lowest negative impact potentials (NIPs) among the
scenarios satisfying all given constraints. The independent variables used to
determine the NIPs and those utilized as constrained criteria were simulated by the
DeNitrification-DeComposition model, which was modified in this study. Due to the
unsatisfactory performance of the model in daily simulations of nitric oxide
(NO) emission and net ecosystem exchange of carbon dioxide (NEE), the model
was modified to (i) newly parameterize the soil moisture effects
on NO production during nitrification, and (ii) replace the original NEE
calculation approach with an algorithm based on gross primary production.
Validation of the modified model showed statistically meaningful agreements
between the simulations and observations in the cotton and W–M fields. Three
BMP alternatives with overlapping uncertainties of simulated NIPs were
screened from 6000 management scenarios randomly generated by Latin
hypercube sampling. All of these BMP alternatives adopted the baseline
(currently applied) practices of crop rotation (3 consecutive years of
cotton rotating with 3 years of W–M in each 6-year cycle), the fraction of crop
residue incorporation (100 %), and deep tillage (30 cm) for cotton. At the
same time, these BMP alternatives would use 18 % less fertilizer nitrogen
and sprinkle or flood-irrigate ∼23 % less water than the
baseline while adopting reduced tillage (5 cm) for W–M. Compared with the
baseline practices, these BMP alternatives could simultaneously sustain crop
yields, annually enlarge the soil organic carbon stock by 4 ‰
or more, mitigate the aggregate emission of greenhouse gases, NO release,
ammonia volatilization, and nitrate leaching by ∼7 %,
∼25 %, ∼2 %, and ∼43 %,
respectively, despite a ∼5 % increase in N2O emission.
However, further study is still necessary for field confirmation of these
BMP alternatives. Nevertheless, this case study proposed a practical
approach to optimize multi-crop system management to simultaneously
achieve multiple United Nations Sustainable Development Goals.
Using a modified DNDC biogeochemical model to optimize field management of a multi-crop (cotton, wheat, and maize) system: a site-scale case study in northern China
