Effects of fertilizer N and number of years in tillage on the protein content of feeding barley straw (cv. Nessa) and on N uptake and recovery

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Abstract
SUMMARY: The effects of six amounts (0, 17, 34, 51, 68 and 85 kg N/ha) of fertilizer N, applied at sowing time as calcium ammonium nitrate, on the crude protein (N × 6·25) content of barley straw 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 total N uptake and apparent recovery of fertilizer N were calculated for each cropping sequence.The mean crude protein content of the 126 sites was 4·1% without N, increasing to 4·8% with 85 kg N/ha. Maximum protein content with 85 kg N/ha ranged from 4·4% in 1971 to 5·4% in 1973. It was highest in the year which gave the lowest straw yields. Protein content was higher when the barley was sown as the first or second crop after pasture than when it was sown as the fourth or later crop. Incremental of fertilizer N gave only small increases or decreases in straw protein contents. Over all sites straw protein content amounted to about 36% of grain protein contents. There was a significant positive relationship between grain and straw protein contents.Nitrogen uptake in the straw without fertilizer N was 19, 18 and 12 kg/ha in barley sown as the first, second and fourth or later tillage crop after grass. The total uptake of N in the grain and straw combined was 93, 102, 107, 109, 111 and 116 kg N from applications of 0, 17, 34, 51, 68 and 85 kg/ha of fertilizer N. The mean apparent recovery of fertilizer N in the straw varied from 12% with 17 kgN/ha to 8% with 85 kg N/ha.