Nitrogen mineralisation rates from chicory-based pastures

The incorporation of chicory (Cichorium intybus) into phased crop-pasture farming systems requires an understanding of the dynamics of nitrogen (N) mineralisation of residues and the potential supply of N to subsequent crops. A 3-year field experiment was conducted to compare relative N mineralisation rates from the pure chicory pasture, compared to the chicory-subterranean clover (Trifolium subterraneum) or lucerne (Medicago sativa)-subterranean clover pastures. Existing pastures were chemically fallowed in either spring or the following autumn. Soil mineral N and soil gravimetric water content were measured at 0, 6 and 12 months after pasture removal. Six months after pasture removal, chicory-subterranean clover pasture exhibited the highest N mineralisation rate for the spring and autumn removals (0.36 and 0.37 kg mineral N ha−1 day−1, respectively), whereas lucerne-subterranean clover pasture had the lowest for the spring and autumn removals (0.04 and 0.05 kg mineral N ha−1 day−1, respectively). However, the daily N mineralisation rate for the lucerne-subterranean clover pasture increased dramatically to 0.51 and 0.98 kg mineral N ha−1 day−1 12 months after pastures were removed in spring and autumn, respectively. In contrast, the chicory pasture produced 0.15 vs 0.63 kg mineral N ha−1 day−1 for the spring and autumn removals, respectively. Including subterranean clover in mixtures with chicory significantly increased the availability of mineral N by 28% with the spring removal and 45% with the autumn removal compared to the pure chicory pasture. Due to the quicker rate of N mineralisation with chicory-based pastures, an opportunity exists to remove chicory-based pastures later than lucerne-based pastures without having a detrimental effect on N supply to the following crop while still providing additional feed for livestock.