Developing a nitrogen fertilizer management model for wheat in calcareous soils using the critical nitrogen dilution curve

Nutr Cycl Agroecosyst https://doi.org/10.1007/s10705-023-10264-2 ORIGINAL ARTICLE Developing a nitrogen fertilizer management model for wheat in calcareous soils using the critical nitrogen dilution curve Ali M. Ali · Ahmed M. Saudi · Ashraf N. El‑Sadek · Bijay‑Singh Received: 5 October 2022 / Accepted: 11 February 2023 © The Author(s) 2023 Abstract The critical nitrogen (N) dilution curve, which expresses whole-plant critical N concentration as a function of shoot biomass, can be used as a N management diagnostic tool for cereals. The objectives of this research were to develop a critical N dilution curve for wheat grown in calcareous soils and to formulate a model for estimating N fertilizer requirement of wheat crop at different growth stages. Six N fertilization rates (0–250 kg N h a−1) were used to induce variability in plant growth throughout six siteyears (three locations at West Delta of Egypt and two seasons [2020/21-2021/22]). Aboveground shoot biomass (W; Mg DM [dry matter] h a−1) and N concentration (Nc; g kg−1 DM) were determined on five sampling dates during the growing season. A critical N dilution curve was developed as: Nc = 50.141W−0.424. The Nc dilution curve was then used to develop a N fertilizer topdressing strategy. The study relied on N nutrition index inferred from the Nc based on N uptake, and instead of relying on a single N recovery A. M. Ali (*) · A. M. Saudi Department of Soil Fertility and Microbiology, Desert Research Center, Cairo 11753, Egypt e-mail: A. N. El‑Sadek Department of Plant Production, Desert Research Center, Cairo 11753, Egypt Bijay‑Singh Department of Soil Science, Punjab Agricultural University, Ludhiana 141004, India efficiency coefficient, a variable N recovery efficiency was developed. This approach increased the hypothetical N requirements at low N application rates while decreased requirements at high N application rates, implying that the Nc dilution curve can be used successfully to estimate the rates of supplemental N application. The developed strategy will provide a solid basis for precisely managing N fertilizer, though challenge ahead at the farm level will be in determining the actual shoot biomass and N concentration. Keywords Wheat · Critical N dilution curve · N nutrition index · N requirements Introduction Nitrogen (N) is crucial to crop production since it is required for photosynthesis-driven energy creation and plant growth. High yield levels of wheat (Triticum aestivum L.) can be achieved only through accumulation of more substantial aboveground dry matter, whereas adequate N absorption is essential for dry matter accumulation (Damisch and Wiberg 1991; Song et al. 2016). Excessive N applications, on the other hand, result in not only reduced yield and quality, but also a significant loss of N fertilizer, resulting in greater production costs and environmental pollution (Raun and Johnson 1999; Fageria and Baligar 2005; Bijay-Singh 2018; Bijay-Singh and Craswell 2021). The global N use efficiency of cereal crops Vol.: (0123456789) 13 Nutr Cycl Agroecosyst has remained alarmingly low at around 42% (Zhang et al. 2015), causing a variety of detrimental effects. Wheat crop used 22.8% of total fertilizer N consumption in Egypt (Heffer et al. 2017), indicating that considerable amounts of N are lost from the soil to the environment. The future of N management is unclear (Lemaire et al. 2019), since historical patterns show considerable differences in N application and N use efficiency among cropping systems (Dobermann and Cassman 2005; Bijay-Singh 2022). Because of variances in N application and crop capacity to consume N, some cropping systems have excess N while others have a deficiency of N (Liu et al. 2010; Bouwman et al. 2013). The critical value approach, diagnosis and recommendation integrated system, and compositional nutrient diagnosis are some diagnostic approaches that have been developed to evaluate the appropriateness of N supply to N demand of a crop (Bates 1971; Walworth and Sumner 1987; Parent and Dafir 1992). However, being focused on estimating N in a specific organ of the plant during a particular growth stage, these approaches are greatly depended upon phenological phases of the crop. Also, these approaches do not account for the dynamics of N in the soil–plant system at various stages of crop growth. Therefore, prediction of N status which can assist farmers in timely altering N fertilizer topdressing strategy is fundamental for improving N management (Cassman et al. 2003; Diacono et al. 2013; Bijay-Singh and Ali 2020; Ali et al. 2020). A crop diagnostic approach based on the allometry between the dynamics of N concentration and biomass accumulation in crops is the critical N (Nc) dilution curve hypothesis. The Nc is the minimum N concentration required for maximum crop growth rate (Ulrich 1952). The concept of the N dilution curve is based on the notion that plant N concentration declines during the course of the growth cycle even when there is an ample supply of N. As illustrated below, Lemaire et al. (1984) described the Nc as a negative power function known as the "dilution curve": Nc = aW −b where Nc is the total N concentration in shoot expressed in g k g−1 DM (dry matter), W is the total shoot biomass expressed in Mg DM ha−1, and a Vol:. (1234567890) 13 and b are the model’s coefficients. For most cereal crops including wheat, rice (Oryza sativa L.), and maize (Zea mays L.), the Nc dilution curves have been developed in different parts of the world (Justes et al. 1994; Colnenne et al. 1998; Plénet and Lemaire 2000; Herrmann and Taube 2004; Li et al. 2012; AtaUl-Karim et al. 2013; Zhao et al. 2017; Zhang et al. 2020). The Nc dilution curve can be utilized to generate its N nutrition index (NNI), a useful function that has been used to successfully assess actual crop yield, quality, and N requirement (NR) (Ziadi et al. 2010; Ata-Ul-Karim et al. 2017; Wang et al. 2020). Greenwood et al. (1990) suggested two broad Nc-shoot biomass relationships: one for C3 species (a = 57.0 and b = – 0.50) and one for C4 species (a = 41.0 and b = – 0.50). Nonetheless, according to Lemaire and Gastal (1997), each species has its own critical N dilution curve. In wheat, the parameters for this allometric function were estimated by Lemaire and Gasal (1997), Ziadi et al. (2010), and Yue et al. (2012) to be a = 48 and b = – 0.34, a = 38.8 and b = – 0.57, and a = 41.5 and b = – 0.38, respectively. Numerous studies have demonstrated that due to variable histological, morphological, and eco-physiological traits, the parameters of the dilution curves vary among different crops. In addition, variations in the Nc curve across species (Justes et al. 1994; Bélanger et al. 2001; Du et al. 2020; Fabini et al. 2020; Wang et al. 2020) and between experimental sites have also been frequently observed (Katsura et al. 2010; Wang et al. 2020). Several recent studies have, in fact, suggested that comparing di (...truncated)