灌水量对京南地区紫花苜蓿生产能力的影响

对种植第3年的紫花苜蓿Medicago sativa进行4种不同灌水量(0、25、50和75 mm/次,全年灌水3次)处理,每茬苜蓿初花期测定各处理的产量、茎叶比、株高及第2、3茬苜蓿的单枝质量。结果表明:在试验前1年(2008年)灌足冬水的情况下,灌水对第1茬产量无显著影响,第2、3茬以及全年产量随灌水量增加而增加,第4茬产量则随灌水量增加而减少,第1~4茬苜蓿株高的变化规律与产量相同;灌水对第1、4茬苜蓿茎叶比无显著影响,第2、3茬茎叶比随灌水量增加而增加;第2、3茬苜蓿分枝质量随灌水增加呈增加趋势,灌水25、507、5 mm/次的分枝质量显著高于不灌水(P0.05)。因此,京南地区种植苜蓿应在第1、第2茬苜蓿刈割后灌水,第4茬苜蓿生长期内不宜灌水,当头年灌足冬水时,返青也可不灌水;在生长季降水总量为390.34 mm下,全年最适宜灌水量为150 mm。

Effects of irrigation amount on alfalfa productivity in south of Beijing

Four irrigation treatments (0,25,50,75 mm per time, 3 times in a year round) were designed to study the productivity response of alfalfa planted 3 years ago in south of Beijing through measuring the yield, leaf to stem ratio, plant height in early flowering stage and dry matter of single plant of second and third harvests. The results showed that if enough water was supplied in last winter, the irrigation treatment did not affect the yield of the first harvest, but the second harvest, third harvest and annual yield increased with the irrigation amount. However, the yield of fourth harvest was reduced. Plant height in all harvesting times showed the same trend with the yield. In addition, the irrigation did not significantly affect the leaf-stem ratio of the first and fourth harvests. Stem-leaf ratio and weight of single branch in the second and third harvesting times increased with the irrigation amount. Therefore, irrigation should be performed after the first and second harvests. it should not be irrigated at the growing period after third harvest and the stage of turning green if irrigated in last winter. The best annual irrigation amount was 150 mm while the rainfall in growing season was 390 mm.