Integrated physiological and agronomic modelling of N capture and use within the plant

Abstract

Today farmers have several constraints to take into account in managing their crops: (i) competitiveness: productivity must be maintained or increased whereas inputs must be decreased, (ii) the environmental consequences of cultural practices: pesticide and fertilizer use must be decreased, and (iii) product quality must be improved and nitrogen nutrition is an important factor in harvest quality. These new constraints sometimes conflict: maximum yield is often obtained with large amounts of N, increasing the risks of N leaching. The determination of rates and dates for nitrogen application must become more precise in this context. Tools are required for the forecasting of crop requirements, the diagnosis of N deficiencies during the crop cycle and breeding of new adapted varieties. Models and diagnosis indicators have been developed to meet these needs, but those relating to nitrogen are often based on empirical relationships. Moreover, the available models and indicators often fail to account for cultivar-specific responses. The improvement of agronomic tools and the breeding of new varieties adapted to new cropping systems should be based on a thorough understanding of the key metabolic processes involved, and the relative contributions of these processes to yield determination in conditions of fluctuating N supply. For both purposes, more information is required about plant and crop N economy. In this paper, the way in which N absorption and use within the plant and crop, plant responses to deficiencies and excesses of nitrogen are taken into account in major agronomic models is described first. The level of sophistication of the modules comprising these models depends on operational objectives. Secondly, the ways in which the most recent molecular plant physiology findings can, and indeed should, be integrated into models at the crop and crop cycle levels are described. The potential value of this approach for improving current agronomic models and diagnostic tools, and for breeding more efficient varieties is also discussed.

Comparative Nitrogen Uptake and Distribution in Corn and Velvetleaf (Abutilon theophrasti)

“…Several models have been used to describe and predict N uptake by two general approaches (e.g., Baldwin et al 1973;ten Berge et al 1994ten Berge et al , 1997Graf et al 1990;Hasegawa and Horie 1996;Jeuffroy et al 2002;Kropff 1993;Lindquist 2001a;Nye and Tinker 1977;Sinclair and Muchow 1995). The first approach comes from solute transport theory, in which nutrient uptake is determined primarily by the predicted solute concentration at the root surface (Baldwin et al 1973;Nye and Tinker 1977).…”

Modeling Nitrogen Uptake in Oilseed Rape cv Capitol during a Growth Cycle Using Influx Kinetics of Root Nitrate Transport Systems and Field Experimental Data

“…However, use of the dilution curve leads to an underestimation of N uptake when soil N concentration is high, suggesting that N uptake at the root level is subject to more complex regulation. This limitation highlights the need to adopt a mechanistic approach to predicting the N uptake by roots from the soil solution and, in a more general sense, to develop a better understanding of the regulation of N uptake as proposed in the review of Jeuffroy et al (2002). Based on kinetic equations, four main classes of transporter systems might exist in plant roots (constitutive high-affinity transport systems [CHATS], inducible high-affinity transport systems [IHATS], constitutive low-affinity transport systems [CLATS], and inducible low-affinity transport systems [ILATS]) and are now clearly described (Okamoto et al, 2003).…”

Suprimento de Nitrogênio para Culturas de Verão pela Aplicação Antecipada em Azevém Pastejado por Ovinos

“…Sendo os fertilizantes nitrogenados responsáveis por grande custo de implantação da cultura do milho, é importante manter a fertilidade do solo e, consequentemente, a viabilidade do sistema de produção. É fundamental aplicar técnicas de manejo capazes de aumentar a eficiência dos insumos, em especial o N, para aproveitar ao máximo os recursos aplicados, diminuindo as perdas (Jeuffroy et al, 2002;Sadras e Lemaire, 2014). Portanto, os sistemas de produção que integram os componentes agrícola e pecuário são de fundamental importância para boa ciclagem dos nutrientes e manutenção da fertilidade do solo.…”

“…Para isso, é necessário realizar o correto manejo do pasto e das práticas de correção da acidez e fertilidade do solo, a rotação de culturas, o uso de genótipos de vegetais melhorados e do sistema plantio direto. Para Jeuffroy et al (2002), para alcançar maiores índices produtivos, os produtores realizam grandes aportes de N no sistema, o que aumenta o risco de perdas por lixiviação. Para aumentar a eficiência de uso dos fertilizantes e reduzir os impactos ambientais, faz-se necessário aumentar a precisão dos volumes de fertilizantes aplicados, assim como dos momentos de sua realização.…”

“…Como nova estratégia para contribuir em uma recomendação de adubação mais precisa, está o índice de nutrição nitrogenada (INN) (Lemaire e Gastal, 2009), uma vez que essa técnica, que utiliza a concentração mínima de N para o máximo crescimento da planta, tem o potencial de indicar o real estado nutricional da cultura e colaborar em melhor ajuste das necessidades de fertilização das culturas no longo de seu desenvolvimento (Jeuffroy et al, 2002).…”