Effects of a winter or spring sowing date on soil nitrogen utilisation and yield of barley following a forage crop of red clover, lucerne or hybrid ryegrass

An experiment tested the hypothesis that the yield and nitrogen content of a spring-cultivated barley (Hordeum vulgare) crop (cv. Riviera) would be higher than for a winter-cultivated barley crop (cv. Pearl) when following 3-year-old swards of either red clover (Trifolium pratense), lucerne (Medicago sativa) or hybrid ryegrass (Lolium hybridicum) maintained and harvested for silage. Four replicate, 15 m × 15 m plots of red clover, lucerne, hybrid ryegrass receiving 250 kg N ha−1 annum−1 (250-N HRG) or hybrid ryegrass receiving 0 N ha−1 annum−1 (Zero-N HRG) were sown on 2 September 2002. On 13 October 2004 and 17 March 2005, half of each plot was ploughed and sown with either winter or spring barley, respectively. Barley was harvested as whole-crop at the dough stage. Soil samples were collected from all plots in autumn 2004, spring 2005 and autumn 2005 for soil mineral N (SMN) analyses and ceramic cups were used to assess nitrate leaching from red clover plots. The grain DM yield of barley was higher when cultivating winter barley compared with spring barley when sown following Zero-N ryegrass (P < 0.05), whereas the grain DM yield was higher when cultivating spring barley compared with winter barley when sown following legumes (P < 0.05). In autumn 2005, following harvest of the barley crops, SMN and soil nitrate-N was higher in soils cultivated the previous autumn compared with soils cultivated in spring 2005 (P < 0.001). SMN was higher (P < 0.05) in red clover plots than Zero-N HRG plots, but there were no differences in SMN among the other treatments (P > 0.05). The total N leached from red clover plots was higher from winter-cultivated barley plots (57 kg N ha−1) compared with spring cultivated barley plots (35 kg N ha−1) (P < 0.01). Overall, the results showed that the best practice to optimise the recovery of SMN by a subsequent cereal crop following legumes in this study was to cultivate and sow barley in spring rather than in autumn whereas, when sowing cereals after ryegrass, the best use of SMN was obtained when cereals were sown in the autumn compared with the spring