18th Congress of the European Society for Agronomy

Sensitivity of nitrogen leaching reduction by winter cover crops to management interventions at landscape scale

Aug 27, 2024, 5:40 PM

15m

Les Horizons (2nd floor) (The Couvent des Jacobins)

Oral Synergies of technologies Modeling N & soil

Speaker

Dr Jingjing Zhang (The New Zealand Institute for Plant and Food Research Limited, New Zealand; Auckland University of Technology, New Zealand)

Description

1. Introduction
   Nitrogen (N) leaching losses to groundwater are an environmental risk in intensively managed agricultural systems. Among others, an adaptation strategy to mitigate such pollution risks is to reduce the fallow (bare soil) period duration by sowing cover crops after the winter grazing of forage crops (Carey et al., 2018). Cover crops can take up excess residual N after previous crops, reduce N concentration in drainage water, and reduce drainage volume through transpiration (Thapa et al., 2018). However, the effectiveness of cover crops to mitigate N leaching depends on plant growth, and is largely influenced by local environmental and soil conditions, in addition with farmer’s management decisions (Malcolm et al., 2022). This makes it difficult to quantify the benefits of cover crop adoption across large areas to inform regional environmental planning.

2. Methods
   In this study, we use a variance-based sensitivity analyses to spatially estimate the contribution of different management factors (plant population and sowing time) to the effectiveness of cover crops to mitigate N leaching losses (Crosetto et al., 2000; Teixeira et al., 2017). The Agricultural Production Systems sIMulator next generation (APSIM-NextGen) oats model was first tested against field data for two New Zealand locations with contrasting climates (Southland and Canterbury) to verify prediction accuracy. The model was then set up to calculate the effectiveness of cover crops to reduce N leaching in relation to a fallow (control) treatment at 5 km resolution considering contrasting management options characterised by sowing times from June to October and populations of 150 and 300 plants/m². Two soil types were considered: 1) a deep stony sand soil, and 2) a very deep, heavy silt loam.

3. Results
   Results showed that the sensitivity to management varied spatially, with considerable share of variability explained through factor interactions, particularly for more complex model outputs such as N leaching amounts. Overall, N leaching losses were more sensitive to sowing time than plant population in both soils, with this pattern being more pronounced in the deep stony sand soil. The results also indicate that the cooler region (Southland) was more sensitive to sowing time than warmer one (Canterbury). In both regions, the sensitivity index of N leaching also exhibited spatial patterns in response to changes in temperature profiles with elevation.

4. Discussion
   These results indicate that cover crops effectiveness to reduce N leaching varies within and across large regions. Similarly, spatial variation in the sensitivity to management parameters differed in response to environmental conditions. Therefore, management interventions should be included in detail in spatial analysis models, to allow more accurately estimate variability in cover crop effectiveness across a landscape.

5. References
   Carey, P. L., Cameron, K. C., Di, H. J., & Edwards, G. R. (2018). Does sowing an oats catch crop reduce nitrate leaching from urine deposition following simulated winter forage grazing? - A growth chamber experiment. Plant and Soil, 431(1), 37–52. https://doi.org/10.1007/s11104-018-3742-2
   Crosetto, M., Tarantola, S., & Saltelli, A. (2000). Sensitivity and uncertainty analysis in spatial modelling based on GIS. Agriculture, Ecosystems & Environment, 81(1), 71–79. https://doi.org/10.1016/S0167-8809(00)00169-9
   Malcolm, B. J., Cameron, K. C., Beare, M. H., Carrick, S. T., Payne, J. J., Maley, S. C., Di, H. J., Richards, K. K., Dalley, D. E., & de Ruiter, J. M. (2022). Oat catch crop efficacy on nitrogen leaching varies after forage crop grazing. Nutrient Cycling in Agroecosystems, 122(3), 273–288. https://doi.org/10.1007/s10705-022-10201-9
   Teixeira, E. I., Zhao, G., Ruiter, J. de, Brown, H., Ausseil, A.-G., Meenken, E., & Ewert, F. (2017). The interactions between genotype, management and environment in regional crop modelling. European Journal of Agronomy, 88, 106–115. https://doi.org/10.1016/j.eja.2016.05.005
   Thapa, R., Mirsky, S. B., & Tully, K. L. (2018). Cover Crops Reduce Nitrate Leaching in Agroecosystems:A Global Meta-Analysis. Journal of Environmental Quality, 47(6), 1400–1411. https://doi.org/10.2134/jeq2018.03.0107