Effectiveness of applying urea solution by furrow irrigation to wheat grown on raised beds of an impervious red-brown earth

The distribution and recovery of urea N (25 kg ha-1) applied in solution by low-flow furrow irrigation to wheat, direct-drilled in rows in 1.5m wide permanent beds of a red-brown earth, was determined using15N labelled fertilizer. This method of fertilizer application resulted in an uneven distribution of applied N across the soil bed. Fertilizer N was recovered mainly in the upper 0.15m horizon of the soil. Forty seven percent of the applied N was recovered in the soil and plants within 0.20m of the point of application. Recovery rapidly decreased with increasing distance from the furrow and less than 4% of the urea N was recovered by the plants in the fourth row, 0.67m from the middle of the furrow. The recovery of fertilizer N in the crop was 23, 28, 47 and 40% at 13, 32, 59 and 86 days, respectively; the corresponding total recovery in the crop plus soil was 77, 91, 87 and 75%; the mean being 83 ± 8%. The results suggest that with this method of fertilizer application and these soil properties the furrows should be less than 0.75m apart in order to get uniform distribution of the fertilizer.