Lucerne (Medicago sativa L.) has a large taproot to store and release starch, carbohydrates and nutrients during the plant's growth. Recommended management of the lucerne crop aims to keep the taproot stable subject to the demands for feed provision and stand longevity. Field experiments were conducted in Victoria, Australia, to examine the effects of recovery period on taproot mass and nutritive status. Both experiments used established SARDI Seven lucerne crops and were either cut every 21 days (short recovery SR) or every 42 days (long recovery LR). At each defoliation, taproots were extracted for determination of DM yield and starch, water‐soluble carbohydrate (WSC) and nitrogen (N) concentration and DM yield. At both sites, WSC and N DM yields along with total taproot DM yield did not change greatly as the experiment progressed. Starch was responsive to herbage accumulation with both concentration and DM yield, increasing when herbage accumulation rates were high and decreasing when herbage accumulation rates were low. At both sites, LR taproots had starch levels equal to or higher than those of SR taproots. We conclude that short intervals between defoliations disrupt the energy cycling between shoots and roots. This is likely to reduce lucerne productivity, particularly during periods of rapid growth.

中文翻译：

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收获间隔影响卢塞恩（苜蓿）主根总产量，淀粉，氮和水溶性碳水化合物

琉森（紫花苜蓿L.）具有很大的主根，可以在植物生长期间存储和释放淀粉，碳水化合物和营养素。推荐的卢塞恩作物​​管理旨在保持主根稳定，以满足饲料需求和长寿。在澳大利亚维多利亚州进行了田间试验，以调查恢复期对主根质量和营养状况的影响。这两个实验都使用已建立的SARDI七种苜蓿作物，每21天（SR的短期恢复）或每42天（LR的长期恢复）进行一次切割。在每次脱叶时，都要提取主根以确定DM的产量，淀粉，水溶性碳水化合物（WSC）和氮（N）的浓度以及DM的产量。在两个地点，随着实验的进行，WSC和N DM的产量以及主根DM的总产量没有太大变化。淀粉对牧草的积累有浓度和干物质产量的响应，当牧草的积累率高时，淀粉增加，而牧草的积累率低时，淀粉下降。在两个地点，LR主根的淀粉含量等于或高于SR主根的淀粉含量。我们得出的结论是，脱叶之间的短暂间隔会破坏芽和根之间的能量循环。这可能会降低卢塞恩的生产力，尤其是在快速增长时期。