Nitrogen Remobilization Efficiency Research Articles

Deficit Irrigation and Split N Fertilization on Wheat and Barley Yields in a Semi-Arid Mediterranean Area

This study investigated the interactive effects of different rates of deficit irrigation and timings of N application on wheat and barley yields since there was no report on this important subject. Field experiments in strip-plot designs using sprinkler line sources were conducted for two years at a semi-arid Mediterranean site. The experiments consisted of 4 and 7 irrigation levels with 3 and 6 N treatments in 4 replicates in 2002-03 and 2003-04, respectively. In both years, there was a significant irrigation-by-N interaction on wheat grain yield but not on barley. In 2003-04, N application at stem elongation and heading produced the highest wheat grain yield at the four higher irrigation levels, but highest yield was obtained when N was applied at sowing and tillering at the two lowest irrigation levels. Nitrogen application at stem elongation and heading also gave the highest grain N content. The existence of interaction due to irrigation-by-timing of N application in wheat but not in barley could be because wheat has a higher N uptake after anthesis but lower nitrogen remobilization efficiency than barley. Results suggested that wheat farmers better apply N at stem elongation and heading for a higher yield and grain N content unless they are not irrigating or irrigate with minimum amount of water.

Accumulation and Translocation of Nitrogen in Spring Cereal Cultivars Differing in Nitrogen Use Efficiency

Since northern European agricultural practices are likely to go toward systems with lower inputs of N fertilizers, it is desirable to develop cultivars with increased yield potential associated with higher nitrogen use efficiency (NUE). This study determined the extent of variation in NUE‐related parameters, specifying the primary traits contributing to the difference in nitrogen remobilization efficiency (NRE) on four spring cereal crops, two‐ and six‐row barley (Hordeum vulgare L.), oat (Avena sativa L.), and wheat (Triticum aestivum L.). Field experiments were conducted in Finland during 2001, 2002, and 2003 under two N regimes (0 and 90 kg N ha−1). Wheat had relatively high N content at maturity even though NUE was low, whereas oat and barley had higher NUE. A comparison of nitrogen harvest index (NHI) and NRE revealed that both were low for wheat, linking this with high N uptake after anthesis, suggesting that in wheat the proportion of the assimilated N used immediately in the developing grain is greater than in barley and oat. There was no strong N translocation from vegetative parts of the main shoots in wheat, which exhibited higher competition for N between vegetative and reproductive organs. Plant breeders could use these findings to their advantage in breeding spring cereal crops that not only produce high yield but also efficiently use available N in northern growing conditions.

Nitrogen Remobilization during Grain Filling in Wheat: Genotypic and Environmental Effects

In wheat (Triticum aestivum L.), nitrogen remobilization from the vegetative organs of the crop to the grains has been shown to depend on environmental factors and genotype. We performed, for a set of 10 winter wheat genotypes, field experiments at six sites over a 2‐yr period. By measuring nitrogen uptake at flowering (NUF from 32–284 kg ha−1), the amount of remobilized nitrogen (REMN from 24–228 kg ha−1) and nitrogen remobilization efficiency (NRE from 0.44–0.92) we were able to determine the effect of genotype and environment on the relationship between REMN and NUF. Environment and genotype had significant effects on nitrogen remobilization and nitrogen remobilization efficiency, which mainly depended on treatment (nitrogen and fungicide) and site. For environments without limiting factor during the grain‐filling period, we found that REMN was not dependent on the genotype and could be estimated by a single two‐parameter linear relationship (REMN = 4.13 + NUF × 0.76, r2 = 0.97). We analyzed the effect of drought stress before and after flowering, high temperature during these periods, nitrogen availability and disease pressure on REMN by comparing observed and estimated REMN. The effect of the environment on the relationship between nitrogen uptake at flowering and nitrogen remobilization depended on nitrogen uptake during grain‐filling period and disease pressure and was also affected by genotype. Disease‐resistant genotypes seemed to be able to keep remobilization efficiency stable in conditions of strong disease pressure, whereas nitrogen remobilization efficiency decreased strongly in susceptible genotypes under the same conditions.

Nitrogen Uptake and Remobilization in Maize Hybrids Differing in Leaf Senescence

Maize (Zea mays L.) is an important cereal crop with multiple uses in the world. Stay‐green hybrids have been developed because of their higher productivity. Few studies have been conducted to evaluate the influence of nitrogen (N) levels on N uptake, remobilization, grain yield and N concentration in stay‐green hybrids compared to senescent ones. Field studies were undertaken in P.R. China on an Ustochrepts soil to determine the effects of N levels and hybrids differing in leaf senescence on grain yield and N concentration, N uptake, remobilization, and residual in vegetative tissues in 1996 and 1997. The stay‐green hybrid ND108 had greater yields than TK5 (intermediate senescing) and ZD120 (fast senescing) under both high (225 kg N ha−1) and low N (0 in 1997 or 45 kg N ha−1 in 1996, respectively) supply. ND108 took up more N than the two other hybrids. Grain N concentration of ND108 did not decrease by low N significantly, excepting the experiment sown in the summer of 1996, when post‐silking N uptake was reduced greatly by the shortened grain filling duration. Nitrogen remobilization efficiency in vegetative tissue was higher in senescent hybrids ZD120 than ND108. Nitrogen retained in the stover at harvest was higher in ND108, which can lead to a deficit of soil N for the next crop if the stover is not returned into soil. It was suggested that, though stay‐green hybrids have been developed for high N conditions, they have advantages over senescent hybrids also under N limited conditions.

Vigor de sementes de populações de aveia preta: II. Desempenho e utilização de nitrogênio

O efeito do vigor das sementes e das possíveis interações com a variação na população de plantas (150, 300 e 450 pl/m2), sobre o desempenho a campo de dois cultivares de aveia preta (Avena strigosa Schreb), e sobre alguns componentes envolvidos na utilização do nitrogênio, foi avaliado neste trabalho. O rendimento biológico na antese e na maturação, a remobilização de nitrogênio, a eficiência de remobilização e de utilização de nitrogênio, a concentração de nitrogênio nos tecidos na maturação e a qualidade fisiológica das sementes produzidas, não foram afetados pela diferença nos níveis de vigor das sementes e pela variação na população de plantas. O rendimento de grãos e os componentes do rendimento não foram afetados pelo nível de vigor das sementes, embora as baixas populações de plantas tenham reduzido o rendimento de grãos. As plantas provenientes de sementes de menor vigor foram mais eficientes na alocação de produtos da fotossíntese nas sementes. A cultivar Embrapa 29 foi menos eficientes na acumulação de nitrogênio na biomassa da parte aérea na época da antese, e na biomassa da parte vegetativa aérea na época da maturação, do que a cultivar Embrapa 140. Ocorreram diferenças genotípicas na resposta ao vigor das sementes para algumas características ligadas a eficiência no uso de nitrogênio. Não foram observadas interações entre níveis de vigor de sementes e populações de plantas.