轮作小麦消减胡麻连作障碍的效应研究

The effect of rotation wheat on reducing continuous cropping obstacle of oil flax

为探讨轮作小麦对胡麻连作障碍的消减作用,通过田间试验研究了轮作小麦对胡麻株高和产量的影响,并通过测定土壤酶活性和土壤水提液化感作用,探寻消减连作障碍的机制。结果表明:重茬种植胡麻导致连作障碍现象突出,表现为连作3 a时株高、出苗率、千粒重和单株产量分别降低14.0%、7.75%、33.8%和43.2%,而第二年轮作小麦可以消减连作障碍,使下茬胡麻株高和产量保持在胡麻连作1 a水平,分别为69.7 cm和1.43 g·株^-1。轮作小麦后土壤过氧化氢酶、脲酶和碱性磷酸酶活性分别为2.41 mL·g^-1·h^-1、2.32 mg·g^-1·d^-1和9.04 mg·g^-1·d^-1,与连作1 a胡麻地土壤酶活性无显著性差异,但连作将使部分土壤酶活性发生较大变化,表现为连作2a后土壤过氧化氢酶、土壤脲酶、碱性磷酸酶的活性分别降低至2.16 mL·g^-1·h^-1、8.18 mg·g^-1·d^-1和2.01 mg·g^-1·d^-1,表明轮作小麦可通过保持部分土壤酶活性消减连作障碍,从而利于下茬胡麻生长。与胡麻连作相比,轮作小麦使土壤水提液对胡麻种子萌发和幼苗生长的化感自毒作用减弱,并表现出综合化感效应为0.21%的促进作用,使发芽指数(46.0)、发芽势(92.0%)、活力指数(3.36)、根长(8.35 cm)及根重(23.17 mg)等指标与CK和TC1处理下无显著性差异,而连作加剧土壤水提液自毒作用,对胡麻种子萌发和幼苗生长的抑制作用增强,且综合化感效应随连作年限增加分别降低至-8.61%和-17.01%,表明轮作小麦可以通过影响土壤自毒作用消减胡麻连作障碍。综上所述,胡麻重茬种植将导致明显的连作障碍,合理轮作小麦有利于维持胡麻地土壤酶活性、降低土壤自毒作用,从而消减胡麻连作障碍的发生。

In order to explore the effects of wheat rotation for reducing continuous cropping obstacle of oil flax,field experiments were conducted. The plant height and yield of oil flax were studied, and soil enzyme activity and the allelopathy of water extracts of soil were analyzed. The results showed that heavy stubble cultivation of oil flax caused the phenomenon of continuous cropping obstacle. Oil flax continuous cropping for three year showed that the plant height, the rate of emergence, the thousand grain weight and the per plant yield decreased by 14.0%, 7.75%, 33.8% and 43.2%, respectively. Wheat rotation eliminated continuous cropping obstacle, so that the plant height and yield remained at the level of first year, which was 69.7 cm and 1.43 g·plant-1, respectively. After wheat rotation, catalase, urease and alkaline phosphatase activities in the soil were 2.41 mL·g^-1·h^-1, 2.32 mg·g^-1·d^-1 and 9.04 mg·g^-1·d^-1, respectively. There was no significant difference between the soil enzyme activity in the soil of continuous cropping of oil flax for one year. Continuous cropping led to major changes in soil enzyme activity. The activity of soil catalase, urease and alkaline phosphatase decreased to 2.16 mL·g^-1·h^-1, 8.18 mg·g^-1·d^-1 and 2.01 mg·g^-1·d^-1 after continuous cropping of oil flax for two years. This indicated that wheat rotation reduced continuous cropping obstacle by maintaining soil enzyme activity, which was conducive to the growth of next stubble oil flax. Compared with continuous cropping of oil flax, rotation with wheat reduced the allelopathy autotoxicity of aqueous extracts from soil on seed germination and seedling growth of oil flax, and showed 0.21% synthesis effect that promoted action. The germination index(46.0), germination potential(92.0%), vitality index(3.36), root length(8.35 cm) and root weight(23.17 mg) were not significantly different from that of CK and TC1 conditions. Continuous cropping enhanced water extractable toxin in soil, which had a negative effect on the germination and seedling growth of oil flax. The synthesis effect was reduced to-8.61% and-17.01% with the increase of years of continuous cultivation, and the inhibition effects were enhanced. It was indicated that rotation of wheat could reduce the continuous cropping obstacle of oil flax by reducing the autotoxicity. In summary, heavy crop cultivation of oil flax led to obvious continuous cropping obstacle. Reasonable rotation with wheat helped to maintain the soil enzyme activity and reduce the autotoxicity of oil flax land, thus, reducing the occurrence of continuous cropping obstacle in oil flax.