农茬口对土壤特性及熟地当归育苗的调控效应

利用高寒草甸生荒地进行当归育苗的传统方式造成严重的水土流失。为了探讨农茬口调控土壤特性继而影响后茬当归育苗的效应,在道地产区甘肃省卓尼县熟地培育农作物茬口后进行当归育苗,测定育苗期土壤特性、成苗数和产量。结果表明,农茬口对后茬当归育苗田土壤特性具有显著影响,与休耕茬田比较,马铃薯、油菜、蚕豆茬田土壤电导率极显著降低, pH显著提高,青稞茬田土壤pH和电导率均降低,农茬口极显著提高了后茬土壤阳离子含量,降低了阴离子含量。各茬口土壤K~+含量依次为青稞蚕豆油菜马铃薯休耕, Na~+含量为马铃薯青稞蚕豆油菜和休耕, Cl~-含量为休耕马铃薯青稞油菜蚕豆。随土层加深,紧实度增加,孔隙度减少,含水量随土层和茬口而异。0～15 cm土层的土质疏松且含水量高则有利于保苗。当归成苗数和苗产量与土壤电导率、Cl~-含量均呈显著负相关;苗产量与pH、K~+含量呈显著正相关,与5～10 cm土层容重呈显著负相关;苗数与0～5 cm土层总孔隙度呈显著正相关。各茬口育成苗产量排序与综合评价指数顺序一致,综合评价指数依次为蚕豆(0.986)油菜(0.682)青稞(0.668)马铃薯(0.297)休耕(0.159)。因此,优异的茬口特性可优化当归幼苗赖以生存的农田土壤环境,改善土壤性质,富集营养,促生保苗,蚕豆茬口更为优异。

Regulated effects of preceding crop on soil property and cultivating seedlings for Angelica sinensis on cultivated farmland

The traditional nursery approach for Angelica sinensis (Oliv.) Diels seedlings in wild alpine meadow causes serious soil erosion. In order to reveal how preceding crop regulates the soil property and affects the subsequent nursery outcome of A. sinensis seedlings, A. sinensis seedlings were cultivated in cultivated farmland with different preceding crops in Zhuoni County, Gansu Province. This region is a geo-authentic habitat for the medical plant. The soil characteristics and seedling yield were measured at the seedling cultivated stage, taking fallow as the control. The rotation crops had significant effects on soil characteristics in the subsequent field of A. sinensis seedlings. Compared with the fallow field, soil conductivity in fields with potato (Solanum tuberosum L.), oil rape (Brassica campestris L.), and broad bean (Vicia faba L.) as preceding crops was significantly decreased. The soil pH was significantly increased, while the soil pH and conductivity in highland barley (Hordeum vulgare var. nudum Hook. f.) field were both decreased. Rotation with crop significantly increased soil cation and decreased anion contents. The K⁺ content in fields with different preceding crops was arranged as highland barley > broad beans > oilseed rape > potato > fallow. Na⁺ was arranged as potato > highland barley > broad bean > rape and fallow. Cl^- was ranked as fallow > potato > highland barley > oil rape > broad bean. As the soil layer deepened, compactness increased and porosity decreased, while the water content varies with the soil layer and the preceding crop. Loose soil with high water content in 0-15 cm layer of soil was beneficial to seedling survival. Seedling numbers and yield were all significantly negatively correlated with soil conductivity and Cl^- content. The seedling yield was positively significantly related to pH and K⁺ content, but was negatively significantly related to bulk density in the 5-10 cm soil layer. Seedling numbers were significantly positively correlated with total porosity in 0-5 cm soil. The ranking of seedling yield under each preceding crop was consistent with the comprehensive assessment index, and the index ranked as broad bean (0.986) > oilseed rape (0.682) > highland barley (0.668) > potato (0.297) > fallow (0.159). Therefore, optimal preceding crop could adequately optimize soil environment in which A. sinensis seedlings rely on. Concerning acquisition strategies, improving soil property, enriching nutrient ions, promoting growth and seedling surviving, broad bean stubble was markedly superior in regulation.