Tomas Persson
Research Professor
(+47) 466 30 485
tomas.persson@nibio.no
Place
Særheim
Visiting address
Postvegen 213, NO-4353 Klepp stasjon
Abstract
Purpose Advanced remote sensing and imagery technology help to estimate variability in grass ley plant coverage (PC). Adjusted manure and fertiliser application rates can be derived according to this variability, by means of machine learning and advanced image processing. This study aimed to determine the effects of variable nitrogen (N) rate from manure and synthetic fertiliser application on a grass ley field experiment in southwestern Norway, thereby generating N rate recommendations. The effects on dry matter yield, N use efficiency, and forage nutritive value were determined. Methods A field experiment was conducted in 2022-2023 and repeated in 2023-2024, estimating PC using digital processing of autumn and spring aerial images to determine fertiliser rates. Three fixed and two variable manure and mineral N rates were applied in early spring and after the first and second cuts. Forage dry matter yield (FDMY) and agronomic N use efficiecy (AgNUE) were evaluated over two seasons. Results A low or variable N rate based on spring coverage led to FDMY and AgNUE comparable to high N rates. Spring and autumn coverage during the second season improved slurry application decisions, offering a valuable tool for grassland management. The N rate-response model effectively represented the nonlinear behaviour of FDMY, revealing a strong concave response to N rates, significant seasonal variations, and a notable flattening of the response in 2024. Predicted curves indicated that the most beneficial N application occurs in earlier cuts, as late-season applications showed diminished yield leverage under 2024 conditions. Conclusion Image analysis can effectively support variable-rate fertiliser recommendations for perennial grasslands, although such approaches only improved N usage in one of two years. Whilst variable-rate application (VRA) is resilient during constrained regrowth years, interannual weather variability and seasonal conditions significantly influenced N responsiveness, indicating the necessity for calibrating cover-based models to enhance nutrient management efficiency under varying climate conditions.
Authors
Mohammad Tirgariseraji A. Pouyan Nejadhashemi Mahmood Sabouhi Sabouni Yaghoob Jafari Tomas Persson Alisher Mirzabaev Alireza Nikouei Kieron Moller Naser Shahnoushi ForoushaniAbstract
Food production is the primary source of nitrogen pollution, which has significantly impacted the nitrogen cycle and exceeded the nitrogen-safe operation space of the planet. The objective of this study is to assess the effectiveness of the Nitrogen Regulatory Policy (NRP) in reducing nitrogen fertilizer use under population pressure for meat, dairy, wheat, and potatoes in the Zayandeh-Rud River basin, Iran. The methodology of this study involves two main components. First, an elasticity criterion was formulated to assess the trade-off between nitrogen fertilizer use and food production capacity. This criterion integrates optimized cropland, the Block of Distributed Calories (BDC), and nitrogen fertilizer use, with food production capacity quantified in terms of the BDC at its optimal level. Second, the simulated distribution of the elasticity criterion was analyzed using Simulation and Econometrics to Analyze Risk (Simetar), defining elastic and inelastic zones to capture the variability in the trade-off under different conditions. The results of this study identified key factors influencing the elastic and inelastic ranges of the elasticity criterion, including technological change, the weight of diet components in dietary preferences, and the diminishing returns of the NRP. The NRP solution aims to reduce nitrogen fertilizer use by targeting a lower application range. It addresses the challenges of fertilizer management under population pressure, specifically for farming systems in the Zayandeh-Rud River basin operating at the ‘diminishing marginal production’ stage. The trade-off between livestock and non-livestock diet components enhances nitrogen fertilizer efficiency under population pressure as long as livestock components remain within the elastic zone and non-livestock components stay within the inelastic zone. The novelty of this study lies in the introduction of the elasticity criterion for nitrogen fertilizer use under population pressure. This innovative metric highlights the risk of ineffective trade-offs between food production capacity and nitrogen fertilizer adjustments, offering a crucial tool to guide sustainable agricultural practices within the defined criterion ranges.
Abstract
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