Effect of amount and quality of previous crop residues on the nitrogen fertiliser response of a wheat crop
1992
Mason, M.G. | Rowland, I.C. (Western Australian Dept. of Agriculture, South Perth)
Burr medic cv. Circle Valley at 3 sowing rates (3, 12, and 50 kg per ha), narrow leaf lupins (cv. Illyarrie) at 2 sowing rates (30 and 100 kg per ha, with the high rate sown early or late) and oats cv. Winjardie at 2 sowing rates (20 and 60 kg per ha, with the high rate sown early or late), were planted on a deep, infertile siliceous sand at Badgingarra, to produce residues of varying quantity and quality (C: N ratio). The residues were incorporated into the soil during the sowing operation of a wheat crop in 1989. Wheat dry matter and grain yields were higher following lupins and medic than following oats, and although there were large responses to N fertilizer following all 1988 crops, the N application had little effect on the difference between oats and legumes. In the absence of N fertilizer, yields and N uptake by the 1989 wheat crop were higher following lupins than following medic, due to hardseededness of medic seeds. There were good correlations between dry matter and grain yield of wheat without N fertilizer and C:N value of the residues. Similar correlations were obtained between dry matter and grain yields and total N content of the residues. Yields decreased with increasing C:N and increased with total N content of the residues. Wheat grain N concentrations fell with the first increment of N fertilizer (which produced a large yield increase) but rose to high levels at high N rates.
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