The effects of six amounts (0, 17, 34, 51, 68, 85 kg N/ha) of fertilizer N, applied at sowing time, on the crude protein (N × 6·25) content of barley grain sown as the first, second and fourth or later tillage crop after grazed pasture were studied over three seasons at a total of 126 sites. In addition, non-protein N in the grain was measured at 24 sites.
The overall crude protein content was 11·3% without N, increasing to 13·4% with 85 kg N/ha. The first increment of 17 kg N/ha gave the least increase in grain protein content. The year which gave the largest yields gave the lowest grain protein contents and vice versa. The mean grain protein contents without N for 1971–3 inclusive were 10·8, 11·5 and 11·8% respectively.
The mean grain protein contents without N when barley was sown as the first, second and fourth or later tillage crop after pasture were 12·6, 11·5 and 10·0% respectively; the corresponding values with 85 kg N/ha were 14·4, 13·9 and 11·8%. There was a positive relationship between grain protein content and lodging, especially in barley sown as the first tillage crop after pasture, where lodging was most severe.
Non-protein N was low and only accounted for 5–8% of the total grain N content. The mean grain. N uptake with no fertilizer N applied was 82, 70 and 49 kg/ha in barley sown as the first, second and fourth or later tillage crop respectively. The apparent recovery of fertilizer N was largest in fourth or later barley.