Nitrogen utilization by forage grasses

The efficient utilization of nitrogen (N) in grass production is essential to reduce the risks of water and air pollution, and the costs of production. Recent findings in grass physiology and agronomy should help in developing new tools to improve N utilization efficiency. A model of N dilution describing the decrease in plant N concentration with increasing shoot biomass under non-limiting N supply is used to define a critical N concentration in grasses required to reach maximum shoot growth and yield. The index of N nutrition (INN) is then calculated as the measured N concentration in a given situation divided by the critical N concentration. The INN is a diagnostic tool to quantify the level of N deficiency during growth cycles, and can also be used in crop modelling and in the interpretation of results from studies conducted over many sites and years. The "universality" of the model of N dilution is based on the increased proportion of structural to metabolic components during crop growth combined with the fact that the structural component has a lower N concentration. Inter- and intra-species differences in N concentration at a given shoot biomass can be related to differences in the proportion of leaves which are assumed to be equivalent to the metabolic component. Under N-deficient conditions, the reduction in grass growth is due to a reduction in the interception of solar radiation primarily through reduced leaf extension, and to a reduction in the conversion efficiency of intercepted radiation into shoot biomass primarily through an effect on biomass partitioning between roots and shoots. The concept of the critical N concentration based on the relationship between plant N concentration and shoot biomass is used to derive general and synthetic expressions of the effect of plant N nutrition on crop growth and crop growth processes. These recent findings on the relationship between N nutrition and the growth of forage grasses should result in the improvement of the efficiency of N utilization by a more precise fertilizer management and the development of more N efficient cultivars. Key words: Physiology, growth, photosynthesis, leaf, partitioning, model

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Relationship between P and N concentrations in timothy

Canadian Journal of Plant Science ◽

10.4141/p97-125 ◽

1999 ◽

Vol 79 (1) ◽

pp. 65-70 ◽

Cited By ~ 35

Author(s):

G. Bélanger ◽

J. E. Richards

Keyword(s):

N Fertilization ◽

Phleum Pratense ◽

Growth And Yield ◽

Shoot Biomass ◽

P Deficiency ◽

P Concentration ◽

N Concentration ◽

Critical P Concentration ◽

The Relationship ◽

Phleum Pratense L

Tools quantifying the status of N and P in plants may help to achieve efficient management of these nutrients and to optimize crop growth and yield. The objective of this study was to establish the relationship between P and N concentrations during the regrowth of timothy (Phleum pratense L.) and, in particular, to estimate the critical P concentration required to diagnose P deficiency. The relationship between P and N concentrations was determined for timothy grown in two experiments conducted with early- and late-maturing cultivars under non-limiting N conditions in spring of 1991 and 1992, and in two experiments with four rates of N fertilization conducted in the spring of 1993 and the summer of 1994. Shoot biomass and P and N concentrations were determined weekly during each regrowth cycle. The P and N concentrations decreased with time in all four experiments. The decrease in P concentration with increasing shoot biomass was generally similar to the decrease in N concentration. The relationship between P concentration and shoot biomass was not different for early- and late-maturing timothy cultivars. This relationship, however, was affected by N fertilization. For a given shoot biomass, increasing N fertilization rates increased P concentration. The relationship between P and N concentrations under non-limiting N conditions is described by a linear relationship (P = 1.46 + 0.069N, R2 = 0.79, P < 0.001, n = 48) in which P concentration (P) and N concentration (N) are expressed in g kg−1 DM. The relationship between P and N concentrations was different under N limiting conditions. For a given N concentration, the P concentration was greater under limiting N conditions than under non-limiting N conditions. Our results show that the critical P concentration for shoot growth is a function of the N concentration in the shoot biomass and the level of N deficiency. The present study provides the relationship required to estimate the critical P concentration which is essential for quantifying levels of P deficiency in timothy, and in developing models to predict the quantity of fertilizer P needed to correct that deficiency. Key words: Phleum pratense L., timothy, nitrogen, phosphorus, grasses

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Critical N concentration can vary with growth conditions in forage grasses: implications for plant N status assessment and N deficiency diagnosis

Nutrient Cycling in Agroecosystems ◽

10.1007/s10705-010-9348-6 ◽

2010 ◽

Vol 88 (2) ◽

pp. 215-230 ◽

Cited By ~ 18

Author(s):

Mónica G. Agnusdei ◽

Silvia G. Assuero ◽

Fernando A. Lattanzi ◽

María A. Marino

Keyword(s):

Growth Conditions ◽

Forage Grasses ◽

N Concentration ◽

Status Assessment ◽

N Deficiency ◽

N Status ◽

Critical N Concentration

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Nitrogen management in wheat based on the normalized difference vegetation index (NDVI)

Ciência Rural ◽

10.1590/0103-8478cr20170743 ◽

2018 ◽

Vol 48 (9) ◽

Cited By ~ 2

Author(s):

André Luis Vian ◽

Christian Bredemeier ◽

Marcos Alexandre Turra ◽

Cecília Paz da Silva Giordano ◽

Elizandro Fochesatto ◽

...

Keyword(s):

Technical Efficiency ◽

Vegetation Index ◽

Normalized Difference Vegetation Index ◽

Field Experiments ◽

Shoot Biomass ◽

Sensor Field ◽

N Dose ◽

Plant Emergence ◽

The Moment ◽

The Relationship

ABSTRACT: Biomass production and nitrogen (N) accumulated in wheat shoots may be used for quantifying optimal topdressing nitrogen doses. The objective of this study was to develop and validate models for estimating the amount of biomass and nitrogen accumulated in shoots and the N topdressing dose of maximum technical efficiency in wheat using the normalized difference vegetation index (NDVI) measured by an active optical canopy sensor. Field experiments were carried out in two years and treatments consisted of N doses applied at plant emergence and as topdressing. NDVI, shoot biomass and N accumulated in shoots at the growth stage of six fully expanded leaves and grain yield were evaluated, being determined the topdressing N dose of maximum technical efficiency (DMTE). The NDVI was positively correlated to shoot biomass and N content in shoots and models for the relationship between these variables were developed and validated. The DMTE was negatively correlated with the NDVI value evaluated at the moment of N topdressing application. Thus, NDVI evaluation by an active optical canopy sensor can be used for nitrogen fertilization in variable rate, allowing the adjustment of applied N doses in different areas within a field.

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Estimating Nitrogen from Structural Crop Traits at Field Scale—A Novel Approach Versus Spectral Vegetation Indices

Remote Sensing ◽

10.3390/rs11172066 ◽

2019 ◽

Vol 11 (17) ◽

pp. 2066 ◽

Cited By ~ 3

Author(s):

Nora Tilly ◽

Georg Bareth

Keyword(s):

Spectral Data ◽

Spring Barley ◽

Vegetation Indices ◽

Structural Data ◽

Crop Growth ◽

Negative Consequences ◽

Field Scale ◽

Crop Height ◽

N Concentration ◽

Dry Biomass

A sufficient nitrogen (N) supply is mandatory for healthy crop growth, but negative consequences of N losses into the environment are known. Hence, deeply understanding and monitoring crop growth for an optimized N management is advisable. In this context, remote sensing facilitates the capturing of crop traits. While several studies on estimating biomass from spectral and structural data can be found, N is so far only estimated from spectral features. It is well known that N is negatively related to dry biomass, which, in turn, can be estimated from crop height. Based on this indirect link, the present study aims at estimating N concentration at field scale in a two-step model: first, using crop height to estimate biomass, and second, using the modeled biomass to estimate N concentration. For comparison, N concentration was estimated from spectral data. The data was captured on a spring barley field experiment in two growing seasons. Crop surface height was measured with a terrestrial laser scanner, seven vegetation indices were calculated from field spectrometer measurements, and dry biomass and N concentration were destructively sampled. In the validation, better results were obtained with the models based on structural data (R2 < 0.85) than on spectral data (R2 < 0.70). A brief look at the N concentration of different plant organs showed stronger dependencies on structural data (R2: 0.40–0.81) than on spectral data (R2: 0.18–0.68). Overall, this first study shows the potential of crop-specific across‑season two-step models based on structural data for estimating crop N concentration at field scale. The validity of the models for in-season estimations requires further research.

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The mathematical model of plant diseases and insect pests and the relationship between the crop growth

Computer, Intelligent Computing and Education Technology ◽

10.1201/b16698-270 ◽

2014 ◽

pp. 1231-1233

Author(s):

Qiang Zhang

Keyword(s):

Mathematical Model ◽

Insect Pests ◽

Crop Growth ◽

Plant Diseases ◽

The Mathematical Model ◽

The Relationship

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Ethephon Reduces Maize Nitrogen Uptake but Improves Nitrogen Utilization in Zea mays L.

Frontiers in Plant Science ◽

10.3389/fpls.2021.762736 ◽

2022 ◽

Vol 12 ◽

Author(s):

Yushi Zhang ◽

Yubin Wang ◽

Churong Liu ◽

Delian Ye ◽

Danyang Ren ◽

...

Keyword(s):

Grain Yield ◽

Plant Density ◽

N Uptake ◽

Utilization Efficiency ◽

N Application ◽

Total N ◽

N Concentration ◽

High Plant Density ◽

Ethephon Treatment ◽

N Use

Increasing use of plant density or/and nitrogen (N) application has been introduced to maize production in the past few decades. However, excessive planting density or/and use of fertilizer may cause reduced N use efficiency (NUE) and increased lodging risks. Ethephon application improves maize lodging resistance and has been an essential measure in maize intensive production systems associated with high plant density and N input in China. Limited information is available about the effect of ethephon on maize N use and the response to plant density under different N rates in the field. A three-year field study was conducted with two ethephon applications (0 and 90 g ha−1), four N application rates (0, 75, 150, and 225 kg N ha−1), and two plant densities (6.75 plants m−2 and 7.5 plants m−2) to evaluate the effects of ethephon on maize NUE indices (N agronomic efficiency, NAE; N recovery efficiency, NRE; N uptake efficiency, NUpE; N utilization efficiency, NUtE; partial factor productivity of N, PFPN), biomass, N concentration, grain yield and N uptake, and translocation properties. The results suggest that the application of ethephon decreased the grain yield by 1.83–5.74% due to the decrease of grain numbers and grain weight during the three experimental seasons. Meanwhile, lower biomass, NO3- and NH4+ fluxes in xylem bleeding sap, and total N uptake were observed under ethephon treatments. These resulted in lower NAE and NUpE under the ethephon treatment at a corresponding N application rate and plant density. The ethephon treatment had no significant effects on the N concentration in grains, and it decreased the N concentration in stover at the harvesting stage, while increasing the plant N concentration at the silking stage. Consequently, post-silking N remobilization was significantly increased by 14.10–32.64% under the ethephon treatment during the experimental periods. Meanwhile, NUtE significantly increased by ethephon.

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MYB61 is regulated by GRF4 and promotes nitrogen utilization and biomass production in rice

Nature Communications ◽

10.1038/s41467-020-19019-x ◽

2020 ◽

Vol 11 (1) ◽

Author(s):

Yihong Gao ◽

Zuopeng Xu ◽

Lanjun Zhang ◽

Shance Li ◽

Shaogan Wang ◽

...

Keyword(s):

Biomass Production ◽

N Uptake ◽

Biomass Accumulation ◽

Nitrogen Utilization ◽

Cellulosic Biomass ◽

Utilization Efficiency ◽

Cellulose Synthesis ◽

N Utilization ◽

C Metabolism ◽

N Use

Abstract Nitrogen (N) is a macronutrient that boosts carbon (C) metabolism and plant growth leading to biomass accumulation. The molecular connection between nitrogen utilization efficiency (NUE) and biomass production remains unclear. Here, via quantitative trait loci analysis and map-based cloning, we reveal that natural variation at the MYB61 locus leads to differences in N use and cellulose biogenesis between indica and japonica subspecies of rice. MYB61, a transcriptional factor that regulates cellulose synthesis, is directly regulated by a known NUE regulator GROWTH-REGULATING FACTOR4 (GRF4), which coordinates cellulosic biomass production and N utilization. The variation at MYB61 has been selected during indica and japonica domestication. The indica allele of MYB61 displays robust transcription resulting in higher NUE and increased grain yield at reduced N supply than that of japonica. Our study hence unravels how C metabolism is linked to N uptake and may provide an opportunity to reduce N use for sustainable agriculture.

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A new approach for determining rice critical nitrogen concentration

The Journal of Agricultural Science ◽

10.1017/s0021859611000177 ◽

2011 ◽

Vol 149 (5) ◽

pp. 633-638 ◽

Cited By ~ 13

Author(s):

R. CONFALONIERI ◽

C. DEBELLINI ◽

M. PIRONDINI ◽

P. POSSENTI ◽

L. BERGAMINI ◽

...

Keyword(s):

Nutritional Status ◽

Cropping Systems ◽

Nitrogen Concentration ◽

Simulation Models ◽

Crop Models ◽

N Concentration ◽

Alternative Approach ◽

Using Data ◽

The University ◽

Critical N Concentration

SUMMARYA reliable evaluation of crop nutritional status is crucial for supporting fertilization aiming at maximizing qualitative and quantitative aspects of production and reducing the environmental impact of cropping systems. Most of the available simulation models evaluate crop nutritional status according to the nitrogen (N) dilution law, which derives critical N concentration as a function of above-ground biomass. An alternative approach, developed during a project carried out with students of the Cropping Systems Masters course at the University of Milan, was tested and compared with existing models (N dilution law and approaches implemented in EPIC and DAISY models). The new model (MAZINGA) reproduces the effect of leaf self-shading in lowering plant N concentration (PNC) through an inverse of the fraction of radiation intercepted by the canopy. The models were tested using data collected in four rice (Oryza sativaL.) experiments carried out in Northern Italy under potential and N-limited conditions. MAZINGA was the most accurate in identifying the critical N concentration, and therefore in discriminating PNC of plants growing under N-limited and non-limited conditions, respectively. In addition, the present work proved the effectiveness of crop models when used as tools for supporting education.

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