Yield formation and plant metabolism of spring barley in response to locally injected ammonium

Schittenhelm, Siegfried GND; Menge-Hartmann, Ute

This study was conducted to elucidate the crop physiological basis for yield differences frequently observed in experiments comparing top-dressing of N fertilizers with injection of ammonium or ammonium/urea solutions into the soil. The effects of diammonium phosphate (NH₄-N) injected at the two-leaf stage, calcium nitrate (NO₃-N) broadcasted and incorporated before sowing, and a control without N fertilization (-N) were assessed from measurements of growth, N-uptake and N-partitioning, light interception, gas exchange, leaf anatomy and the activity of key enzymes of N-metabolism. The experiment was performed with spring barley (Hordeum vulgare L.) grown in 80-l containers in a vegetation hall in Braunschweig, Germany. The plants in the NH₄-N treatment produced a 20 % higher grain yield than those in the NO₃-N treatment. The grain yield superiority of the NH₄-N plants was attributable to a higher number of ears per plant (+13 %) and more grains per ear (+6 %). The NH₄-N plants exhibited lower concentrations of inorganic cations than plants supplied with NO₃-N. In the NH₄-N treatment, the light penetrated more deeply into the crop canopy and the NH₄-N plants exhibited a higher leaf carbon exchange rate at the different leaf layers than the NO₃-N plants. It is concluded that as opposed to predominantly nitrate nutrition, provision of a persistent source of ammonium enables plants to take advantage of the positive yield effect of mixed N nutrition. © 2006 Blackwell Verlag.

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Schittenhelm, Siegfried / Menge-Hartmann, Ute: Yield formation and plant metabolism of spring barley in response to locally injected ammonium. 2006.

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