Fertilizer and soil nitrogen accumulation by irrigated barley grown on a red-brown earth in south-eastern Australia

• Published in: Plant and soil 1989-09, Vol.119 (1), p.155-161
• Main Authors: Smith, C.J. (Institute for Irrigation and Salinity Research, Tatura, Vict. (Australia)), Gyles, O.A
• Format: Article
• Language: English
• Subjects: Agricultural site preparation; Agrology; ANALISIS DEL SUELO; ANALYSE DE SOL; AUSTRALIA; AUSTRALIE; AZOTE; Barley; Clay soils; Fertilizers; HORDEUM VULGARE; Irrigated soils; IRRIGATION; Minerals; NITROGEN; NITROGENO; RIEGO; SOIL TESTING; Sowing
• ISSN: 0032-079X; 1573-5036
• DOI: 10.1007/BF02370280

¹⁵N labelled (NH₄)₂ SO₄ was applied to barley at 5 g N m⁻² (50 kg N ha⁻¹) in microplots at sowing to study the timing of the N losses and the contribution of soil and fertilizer N to the plant. Water treatments included rainfed and irrigation at 45-50 mm deficit beginning in the spring. Recovery of ¹⁵N in the plant increased to a maximum of about 20% within 91 days after sowing (DAS 91) and then remained constant. Approximately 16% (0.8 g N m⁻²) of the fertilizer was in the stem and leaves at DAS 91 and this N was subsequently redistributed to the head. At maturity, approximately 75% of the ¹⁵N assimilated by the tops was recovered in the grain. Soil N contributed 3.6 g Nm⁻² to the head; 2.2 g N m⁻² was remobilized from the stem and leaves, and the balance, approximately 1.4 g N m⁻², was taken up from the soil between DAS 69 to 91. Effects of irrigation treatments on N accumulation were not significant. Residual ¹⁵N fertilizer in the soil decreased with time from sowing, and at maturity 40% of the applied N was recovered in the surface 0.15 m. ¹⁵N movement to depth was limited and less than 5% of the fertilizer was recovered below 0.15 m. Irrigation had no effect on the ¹⁵N recovery at depth. Total recovery of the ¹⁵N varied between 60 and 67% and implies that 33-40% was lost from the soil-plant system. The total recovery in the soil and plant was not affected by time or irrigation in the interval DAS 39 to 134. Losses occurred before DAS 39 when crop uptake of N was small and soil mineral N content was high. There was an apparent loss of 1.9 g fertilizer N m⁻² (i.e. 38% of that applied) between DAS 1 and 15. This loss occurred before crop emergence when rainfall provided conditions suitable for denitrification.