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Effect of nitrogen on yield and protein content of oats

K. Bishop and C. Bluett

Department of Agriculture, Ballarat VIC 3350

In high rainfall areas of Victoria oats are grown as a source of conserved fodder for livestock. Yields are often high, but widespread use of feed testing services has led to the realisation that grain protein levels are often low. Oats frequently need supplementation with a grain legume, commonly lupins, when fed to young sheep or ewes. In 1988 and 1989 experiments to try to increase yield and protein by the application of nitrogen fertiliser were conducted at Ballarat. The results of the 1988 trial are presented here.


Two cultivars, Echidna (Ech) and Mortlock (Mor), and an Echidna x Mortlock crossbred (X B) were sown in May at 80 kg/ha with 200 kg/ha superphosphate (9.1% P). Nitrogen was applied as "Pivot Green N" (32% N), (a solution of urea and ammonium nitrate), sprayed onto the plots with flooding nozzles, mixed with water at a different ratio for each rate. 50 kg N/ha was applied as the base rate to all non-control treatments at late tillering (GS 35) and treatments of 0, 25, 50 and 75 kg N/ha were topdressed at the early milk stage of grain development (GS 75). The experiment design was a randomised block with four replicates.


In 1988 increasing nitrogen rate resulted in a progressive decline in yield. Protein levels rose with increasing nitrogen except at the highest rate where some decline occurred. Increases of 2.2-2.5% protein were achieved while yields decreased by 0.3-0.8 Oa.

Figure 1. Effect of nitrogen on (a) protein % and (b) yield of oats.


A wet autumn and winter was followed by a dry spring. Foliar fertiliser caused severe leaf burn and plants had trouble recovering from this until late in the growing period. Increased protein content of grain reduces the amount of lupins needed to achieve desired protein content of livestock rations. Under experimental conditions in 1988, the saving in purchased lupins because of increased oat protein did not compensate for the value of the yield lost. In the 1989 experiments, protein levels were again increased, and although yields were variable, some increases were achieved. This indicates that seasonal variation will influence the viability of applying nitrogen fertiliser to increase grain yield and protein.

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