Water stress due to increased intra-annual precipitation variability reduced forage yield but raised forage quality of a temperate grassland

Modelling above-ground herbage mass for a wide range of grassland community types

Historically, the agronomic focus of crop mineral nutrition has yielded responses to individual elements (N, P, K…) to determine the economically optimum fertilization rates. This “prognostic” approach required several parameters for crops, climates, and soils that are often estimated with large uncertainty leading to over-fertilization and environmental problems in some systems (e.g., maize in China), and under-fertilization and soil mining in other systems (e.g., wheat in Australia). In this review, an alternative approach is developed for reducing the uncertainty intrinsically linked to this prognostic approach. Our approach is based on four propositions: (1) the evidence of an allometry between the metabolic shoot mass (scaling with leaf area) and the structural shoot mass (supporting and vascular tissues) within plants that allows the formulation of critical N dilution curves and the determination of the Nitrogen Nutrition Index (NNI) for estimating the N nutrition status of field crops; (2) the co-regulation of crop N uptake dynamics by both soil N supply and crop N demand in relation with its growth capacity that allows a better, more generalizable estimation of timing and rate of fertilizer; (3) a better understanding of the effects of genotype–environment–management interactions on N use efficiency in cropping systems reducing then drastically uncertainties linked to the classical prognostic approach for N fertilization; (4) as P and K also relate allometrically with biomass, P and K concentrations can be directly related to N concentration for the formulation of a multi-element diagnosis of crop nutrition. Here, we develop the theoretical background supporting these four propositions and outline implications for both fertilization management and crop phenotyping.

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Allometric approach to crop nutrition and implications for crop diagnosis and phenotyping. A review

Timothy (Phleum pratense L.) is a widely grown fo rage grass species in cool and humid regions of the world including northeastern and northwestern North America, Nordic countries, Russia, and Japan. The nutritive value of timothy decreases with time, phenological development, and increasing forage yield. This review paper summarizes methods of controlling or improving the nutritive value of timothy through management practices and genetic selection, while keeping in mind the importance of forage yield. Consequently, the nutritive value of timothy is considered in relation to the accumulation of forage yield. The ecophysiological basis for the decrease in nutritive value with increasing forage yield during a growth cycle is presented with the assumption that the forage is made of two components: metabolic and structural. The decrease in the proportion of the metabolic component with increasing forage yield reduces the nutritive value of timothy. The nutritive value is also affected by the N concentration ...

Improving the nutritive value of timothy through management and breeding

Water use efficiency in perennial forage species: Interactions between nitrogen nutrition and water deficit

(…) La secheresse provoque une augmentation de la digestibilite, correlativement a une reduction de la teneur en ADF et un accroissement de la teneur en azote dans la biomasse aerienne, car la part des feuilles est plus elevee en culture seche. En effet, la relation entre la composition morphologique (rapport feuilles/tiges) et le niveau de production n'est pas modifiee. Cela explique en partie l'accroissement de la valeur energetique du fourrage (…) La secheresse tend a induire un deficit de nutrition azotee compense ou non par l'accroissement de la part des feuilles, selon le niveau de limitation de la croissance

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J.-L. Durand

Papers

Effet de la sécheresse sur la digestibilité in vitro, la teneur en ADF et la teneur en azote de la luzerne (Medicago sativa L.)