Nitrogen use efficiency

1. P1
Nitrogendynamics of chickpea:Effects of cultivar choice, N fertilization,
Rhizobiuminoculation, and cropping systems
Gan et al.,2010 Can.J. PlantSci.90: 655666.
UnderstandingN dynamicsinrelationtocultural practicesmay help optimize N management in annual
legume crops. This study was conducted at six environ sites (locationyear combinations) in southern
Saskatchewan, 20042006, to quantify N uptake, N2 fixation, and N balance in chickpea (Cicer
arietinum L.) in relation to cultivar choice, cropping systems, rhizobial inoculation, and soil N fertility.
The cultivars Amit, CDC Anna, CDC Frontier, and CDC Xena were grown at N fertilizer rates of 0, 28, 56,
84, and 112 kg N ha1 with no Rhizobium and at 0, 28, and 84 kg N ha1 combined with Rhizobium
inoculation,evaluatedinbothconventional tilled-fallow andcontinuously cropped no-till systems. Flax
was usedasa nonN-fixingreference crop.The cultivarCDCXenahadthe lowestyield (1.57 Mg ha1 ) and
seedN uptake (54.4 kgN ha1 ),withN use efficiency(NUE, 13.2 kg seed N kg1 ) being 17% less than the
average of the other cultivars. Consequently, N balance (N input via fertilizer and N-fixation minus N
exported) was32.4 kg N ha1 for CDC Xenaandlessnegative thanthe average of the othercultivars(39.8
kg N ha1 ). Inoculated chickpea took up 10 kg ha1 more N into the seed and 5 kg ha1 more N into the
straw than chickpea that was not inoculated. The amount of N fixed as a percentage of total N uptake
was 15% for non-inoculatedchickpeaand 29% for inoculatedchickpea, resultinginnegative N balance
regardless of cropping system. Increasing N fertilizer rates decreased NUE, with the rate of decrease
being greater for noninoculated chickpea compared with inoculated chickpea. We conclude that
optimumproductivityof chickpea can be achieved with application of effective Rhizobium inoculants,
and that bestN managementpracticesmustbe adoptedinthe succeedingcropsdue to a large negative
N balance after a chickpea crop.
P2
Nitrogen yield and nitrogen use of chickpea compared to pea, barley and oat in
Central Europe
Neugschwandtner et al., 2015 International Journal of Plant Production 9 (2)
Europeanagriculture suffersfromasubstantial deficitof proteinsourcesfor livestockand the projected
changesinagro-climaticconditionsinCentral Europe include a higher risk of drought. To address these
challenges, the drought resistant legume crop chickpea was compared with pea, barley and oat
regarding its nitrogen (N) yield, protein yield and N use and utilization efficiency under Central
European growing conditions. The two year trial was conducted in eastern Austria with calcium
ammonium nitrate or the depot fertilizer Basacote® Plus 6M at two levels of N rate each besides an
unfertilizedcontrol. In2006, chickpeahadthe lowestgrainyieldandgrainN yieldamong the four crops
while under drought conditions in 2007 chickpea attained a higher grain protein yield that surpassed
those of barley and oat. Under both, the more humid conditions in 2006 and the drier weather in

2. 2007, chickpea maintained a constant partial factor N use efficiency (PFNUE: grain yield per unit
fertilizer N) and a consistently high N utilization efficiency (NUtE: grain yield per unit N in the above-
ground dry matter) for grain production whereas these parameters were severely decreased by
drought with pea, barley and oat. Results indicate that chickpea could be an alternative in a future
more dry climate for achieving a reasonable protein yield in Central Europe through its ability to
maintain high PFNUE and NUtE under conditions of drought.
P3
Nitrogenuse efficiency (NUE) inrice links toNH4
+
toxicity and futile NH4
+
cycling
in roots
Chen et al., 2012 Plant Soil DOI 10.1007/s11104-012-1575-y
Rice is knownasan ammonium(NH4
+
)-tolerantspecies. Nevertheless, rice can suffer NH4
+
toxicity, and
excessive use of nitrogen (N) fertilizer has raised NH4
+
in many paddy soils to levels that reduce
vegetative biomassandyield.Examiningwhether thresholds of NH4
+
toxicity in rice are related to nitto
nitrogen-use efficiency (NUE) is the aim of this study.
Methods A high-NUE (Wuyunjing 23, W23) and a low-NUE (Guidan 4, GD) rice cultivar were cultivated
hydroponically, and growth, root morphology, total N and NH4+ concentration, root oxygen
consumption, and transmembrane NH4+ fluxes in the root meristem and elongation zones were
determined.
Results We show that W23 possesses greater capacity to resist NH4+ toxicity, while GD is more
susceptible. We furthermore show that tissue NH4+ accumulation and futile NH+ cycling across the
root-cell plasma membrane, previously linked to inhibited plant development under elevated NH4+,
are more pronounced in GD. NH4+ efflux in the root elongation zone, measured by SIET, was nearly
sevenfold greater in GD than in W23, and this was coupled to strongly stimulated root respiration. In
both cultivars, root growth was affected more severely by high NH4+ than shoot growth. High NH4+
mainlyinhibitedthe development of total rootlengthandroot area, while the formation of lateral roots
was unaffected.
Conclusions Itisconcludedthatthe larger degree of seedlinggrowthinhibition in low- vs. high-NUE rice
genotypes is associated with significantly enhanced NH4+ cycling and tissue accumulation in the
elongation zone of the root.
P4
Effect of Rhizobium inoculation and nitrogen fertilization on yield and protein
content of six chickpea (Cicer arietinum L.) cultivars in marginal soils under
irrigation
Hadi & Elsheikh., 1998 Nutrient Cycling in Agroecosystems 54: 57–63, 1999

3. A field experiment was carried out for two consecutive seasons 1994/95 and 1995/96 at ElRwakeeb (a
sandy clay loam) to study the effect of Rhizobium sp. (Cicer) inoculation and N fertilization on six
chickpea cultivars (Baladi, Gabel marra, NEC 25–27, NEC 2010, ILC 1919, and Flip 85–108). Plants were
either inoculated with three Rhizobium sp. (Cicer) strains (TAL 480, TAL 620 and TAL 1148) separately,
or N fertilized(50 kg N ha−1). The resultsof the two seasons indicated the absence of infective strains
for chickpeainthe soil. Rhizobiuminoculationor N fertilizationsignificantlyincreasedthe total nodule
number per plant, 100 seed weight, yield and protein content of seeds. The results indicated that the
three Rhizobium strains are infective and effective in nitrogen fixation. Inoculation with Rhizobium
strain TAL 1148 resulted in a significant increment in most of the parameters studied, compared to
other strains and untreated control. Cultivar ILC 1919 was the best yielding cultivar, whereas, cultivar
NEC 2010 contained the highest protein content, however cultivar Gabel marra showed the highest
amount of proteindue to inoculationor N fertilization,inthe two seasons.InoculationwithRhizobium
strain TAL 1148 increased yield by 72 and 70%, whereas, 50 kg N ha−1 increased it by 70 and 69% in the
first and second seasons, respectively. The amounts of protein accumulated (kg ha−1) due to N or
Rhizobiuminoculationwere determinedforall cultivars.The resultsobtainedfromthe inoculationwere
comparable to those of 50 kg N ha−1.
(CONCLUSION FROM P1 & P4, RHIZOBIUM INOCULATION INCREASES NUE IN CHICK PEA)
P5
Heterotrimeric G proteins regulate nitrogen-use efficiency in rice
Sun et al., 2014 Nature Genetics
The drive toward more sustainable agriculture has raised the profile of crop plant nutrient-use
efficiency. Here we show that a major rice nitrogen-use efficiency quantitative trait locus (qNGR9) is
synonymous with the previously identified gene DEP1 (DENSE AND ERECT PANICLES 1). The
different DEP1 alleles confer different nitrogen responses, and genetic diversity analysis suggests
that DEP1 has beensubjectedtoartificialselectionduring Oryzasativaspp.japonicarice domestication.
The plantscarrying the dominantdep1-1allele exhibit nitrogen-insensitive vegetative growth coupled
withincreasednitrogenuptakeandassimilation,resulting in improved harvest index and grain yield at
moderate levelsof nitrogenfertilization.The DEP1proteininteracts invivowithboththe Gα (RGA1) and
Gβ (RGB1) subunits, and reduced RGA1 or enhanced RGB1 activity inhibits nitrogen responses. We
conclude that the plant G protein complex regulates nitrogen signaling and modulation of
heterotrimeric G protein activity provides a strategy for environmentally sustainable increases in rice
grain yield.