灌水次数、播种密度对留种紫花苜蓿生长发育和种子产量的影响

The Effects of Irrigation Times and Sowing Density on the Growth and Seed Production of Alfalfa

３年的试验结果表明，一年龄苜蓿春播当年即可获得较高的种子产量。生长第２年由于植株花期倒伏造成种子严重减产，其原因是倒伏影响了昆虫的授粉，同时新生枝条迅速生长，削弱了生殖生长的营养供应。倒伏与植株生长发育特点及灌水密切相关。苜蓿根颈逐年增大导致单株枝条数大幅度增加，易造成植株疯长倒伏。对多年龄苜蓿采用切根处理能显著减少单株枝条数，减轻倒伏程度。多年龄留种苜蓿在蕾期和花期避免灌水可减轻倒伏程度，在荚期灌一水即可。苜蓿种子田适宜的建植密度应在５．５５万株／ｈｍ２左右。

The results of three-year experiments suggest that a relatively high seed yield of alfalfa could be harvested in the first year after sowing in the spring. In the second year, however, the seed yield was significantly reduced by the poor pollination due to the plant lodging during the flowering period and a weaker nutrients supply to the reproductive growth caused by the rapid growth of new shoots. The alfalfa lodging has relations with its growing nature and irrigation management as well. As the aged alfalfa root crown becomes thicker, rapid growth of shoots leads to lodging. Cutting shoots can release aged alfalfa from lodging. Irrigation should be avoided for aged alfalfa during the budding and flowering periods, but it is needed once in the podding stage. The suitable density for alfalfa seed production field should be around 55 550 plants/ha.