不同土壤湿度下稗草对大豆根瘤固氮的影响

Effect of Barnyardgrass on Nitrogen Fixation of Soybean under Various Soil Moisture

在全自控人工气候室内系统研究了不同土壤湿度下稗草对大豆根瘤固氮的影响。结果表明,稗草在每盆3株的密度下,使播后53～63天淹水期间及淹水期后一天的大豆单株根瘤固氮量平均分别比无草对照提高了16.6%和30.0%,在每盆10株的密度下分别使其比无草对照提高了34.2%和67.5%。播后30～70天,在不淹水的情况下,稗草在每盆3株和10株的密度下使其所在处理的平均日蒸发蒸腾量分别比无草对照增加了23.8%和50%,从而削弱了水分对大豆植株的供应;而当土壤水分供应水平从其田间持水量的80%降低到35%时,大豆根瘤的氧气传导速率从0.38cm·s^(-)下降到0.20cm·s^(-1),净光合速率从18.81mg·dm^(-2)·h^(-1)降低到4.04mg·dm^(-2)·h^(-1);每盆10株稗草对大豆单株根瘤重量及每克根瘤固氮酶活性的抑制率则分别从8.2%和17.0%升高到18.3%和19.6%,其对大豆单株根瘤固氮量的抑制率也随之从21.5%上升到33.1%。

Experiments were conducted in phytotron to study the effect of barnyardgrass on nitrogen fixation of soybeans under various soil moisture. Barnyardgrass growth at density of 3 plants/pot increased the nitrogen fixation during the flooding period between 53 and 63 days after planting and 1 day after the flooding by 16.6 and 30. 0% and at density of 10 plants/ pot by 34.2 and 67.5%.respectively.Barnyardgrass increased the evapotranspiration by 23.8% at density of 3 plants/pot and 50% at density of 10 plants/pot and reduced the soil moisture markedly.As soil moisture decreased from 8o% to 35% FC.soybean nodule oxygen conduc- tance rate decreased from 18.81 to 4.04 mg·dm^(-2)·h^(-1).inhibition rate of barnyardgrass to soybean nodulation and nitrogenase activity at density of 10 plants/pot rose from 8.2% and 17.0% to 18.3% and 19.6%.respectively,so that barnyardgrass inhibition effect on nitrogen fixation per soybean plant increased from 21% to 33.1%.