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Effect of lupin and barley rotations on grain yield and soil nitrogen

W.A. Hawthorne and D.C. Lewis

Department of Agriculture, Struan, South Australia. 5271.

Lupins are grown on deep silicious sands (Uc 1.21; Northcote 1971) in the south east of South Australia in the belief that they increase soil nitrogen. Rotations of lupin, barley, sown pasture and existing (bracken infested) pastures commenced in 1976 to examine yields and soil nitrogen status.

Barley yields were highest following a lupin crop and lupins gave highest yields following barley (Table 1). The crop grown two years previously had no influence on the yields in 1978 except that lupins following lupins appear to yield better if barley had been grown previously. Consecutive lupin crops were free of diseases.

TABLE 1. Crop yield (t/ha) as influenced by the preceding crop

Although barley gave higher yields following lupins. this cannot be entirely attributed to increased soil nitrogen. Total soil nitrogen values in plots after harvest indicate highest levels in the existing pasture plots (Table 2).

TABLE 2. Total soil nitrogen (kg/ha in top 10 cm soil) after one crop of barley or lupins, compared with existing pasture.

It appears that when renovating bracken infested pastures on deep sands the first crop sown should be the one having the least value since the second crop is always better. Cropping lupins does not appear to consistently increase soil nitrogen relative to existing poor pastures on deep sand.

Northcote, K.N. (1971) - "A Factual Key for the Recognition of Australian Soils". (Rellin Technical Publications, Glenside).

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