The narrow-leafed lupin (Lupinus angustifolius L.) as a nitrogen-fixing rotation crop for cereal production. III. Residual effects of lupins on subsequent cereal crops

Abstract

The effect of the narrow-leafed lupin (Lupinus angustifolius L.) on growth and production of subsequent cereal crops was studied at three sites on the acidic, N-infertile soils of the Pilliga Scrub region of northern New South Wales.Beneficial effects of lupins on dry matter production were evident in either one (Kamala, Florida A) or two subsequent crops of wheat (Florida B). In the absence of fertilizer N, wheat following lupins outyielded wheat following wheat by an average of 57%. At Florida B, the second wheat crop following lupins outyielded the wheat only plots by 35%. The response to lupins was established early in vegetative growth and was essentially maintained. Effects of lupins on grain yields, evident at all sites in the first crop, were maintained at the two Florida sites for a second crop. Increases in the absence of fertilizer-N were between 0.29 and 1.22 t ha-1 (55 and 145%) (crop 1) and as great as 0.39 t ha-1 (38%) in year 2. Barley responded similarly with increases of 127 and 47% in years 1 and 2, respectively. Amounts of fertilizer required to raise the yields of wheat following wheat to those of wheat following lupins ranged between 40 and 80 kg ha-1. Effects of lupins on protein concentration of cereal grains were inconsistent; largest effects were achieved through N fertilization. Both the incidence and severity of root diseases at Florida A were reduced in the rotation plots; the effect persisted into the third wheat crop following lupins. Disease control was not a factor in the lupin effect at Kamala. Nitrogen budgets for the unfertilized wheat-wheat and lupinwheat sequences at Kamala and Florida A indicated that lupin cropping (i) resulted in potential net gains of soil N of 128 (Kamala) and 29 kg ha-1 (Florida A), and (ii) increased N yields of the following wheat crops by 37 (Kamala) and 20 kg ha-1 (Florida A).