Evidence for differences between winter wheat cultivars in acquisition of soil mineral nitrogen and uptake and utilization of applied fertilizer nitrogen

Abstract

The response of cultivars to applied nitrogen was examined in 11 seasons, 1982–92, in two experiments per year, normally testing seven cultivars at seven rates of fertilizer nitrogen. In all, 27 cultivars were tested in 22 experiments throughout Nottinghamshire, Lincolnshire, Northamptonshire and Suffolk. Cultivars ranged in their date of introduction from Maris Huntsman (1969) to Hereward (1988). For each cultivar in each experiment, the economic optimum yield (Yopt), the amount of fertilizer N needed to produce it (Nopt), the grain %N at Nopt, the offtake of N in the grain at nil N (Noff(N0)) and Nopt (Noff(opt)) and the estimated recovery of fertilizer in the grain at Nopt (AFRopt) were estimated by fitting linear plus exponential curves to data for grain yield and two-straight-line models to data for grain N offtake. From cross-site analysis, normalized cultivar means were calculated for each variate. Over the 20-year period relating to the cultivars in the trial, the contribution of new genotypes to grain yield improvement was 1·92 t/ha, Yopt increasing by 96 kg/ha per year. There was no change in grain %N at Nopt. The effect of changes through breeding from 1969 to 1988 was to increase Noff(opt) by 42 kg/ha (2·1 kg/ha per year), that was associated with a decrease in Noff(N0) (equivalent of soil N offtake) of 15 kg/ha (0·77 kg/ha per year). Part of the increased requirement for fertilizer N was fulfilled by an increase in AFRopt of 18% over the 20-year period. The net effect was for Nopt itself to increase by 56 kg/ha (2·8 kg/ha per year). Since survey evidence indicates no general increase in N use on wheat by farmers since the mid-1980s, it appears that current fertilizer use by farmers may be underestimating the requirement for N now. Alternatively in previous years N requirements may have been overestimated. The change in N available for loss to the environment, from the balance of grain Noff(opt) and Nopt, was from 11 kg N/ha in 1969 compared to 25 kg N/ha in 1988. It seems possible that the potential increase in nitrate levels in groundwater associated with plant type may not have been realised because farmers have conserved the amount of N they use.

Eficiência de uso de nitrogênio em cultivares de trigo pioneiras e modernas

“…Em doses intermediárias de N, houve progresso genético de aproximadamente 0,43% ao ano (R 2 =0,66) para a ERN. Esses resultados evidenciam a necessidade de cautela com a adubação nitrogenada excessiva na cultura do trigo, para que não ocorra consumo de luxo do nutriente (Foulkes et al, 1998;Gaju et al, 2011).…”

“…As alterações em FARN sugerem mudanças na capacidade de absorção de N pelas plantas, possivelmente ligadas à capacidade de absorção da raiz (King et al, 2003;Foulkes et al, 2004) e à tendência de cultivares modernas apresentarem maior período de perfilhamento, o que aumenta o período de absorção de N (Foulkes et al, 1998).…”

“…Com doses baixas, a EAN explica a maior parte da resposta observada em EUN (Ortiz-Monasterio et al, 1997;Foulkes et al, 1998;Le Gouis et al, 2000), enquanto que, em doses altas, destaca-se a importância da EUtN (Brancourt-Hulmel et al, 2003). Entretanto, não há consenso entre os diferentes estudos, pois tanto a EAN quanto a EUtN podem contribuir para o incremento da EUN (Barraclough et al, 2010;Le Gouis et al, 2010;Gaju et al, 2011).…”

“…Normalmente, as cultivares de trigo são desenvolvidos sob baixa pressão de seleção quanto aos componentes da EUN (Górny et al, 2011). Estudos apontam para a adaptação de cultivares modernas à baixa disponibilidade de N, mesmo que estas tenham sido desenvolvidas em ambientes com elevada disponibilidade do nutriente (Ortiz-Monasterio et al, 1997;Foulkes et al, 1998;Reynolds et al, 1999;Guarda et al, 2004;Górny et al, 2006).…”

Plant mineral accumulation, use and transport during the life cycle of plants: A review

“…Nitrogen uptake is affected by changes in the N content or composition in the media (Wang and Crawford 1996;Morgan and Jackson 1988;Foulkes et al 1998) and carbohydrate (Champigni and Tolouizte 1986) within the root as well as by N demand of the shoot (Imsande and Touraine 1994). Nitrogen uptake in plants i.e.…”