Effects of cover crops on soil hydraulic properties and yield in a persimmon orchard

ABSTRACT This study evaluated the effects of cover crops on yield and soil hydraulic properties of a persimmon orchard in Turkey. Soil samples were taken from 0-20 and 20-40 cm. Profiles of a clay soil and field capacity, permanent wilting point, available water capacity and saturated hydraulic conductivity of the samples were determined. Festuca rubra subsp. rubra, Trifolium repens, Festuca arundinacea, a mixture of them [Trifolium repens (40%) + Festuca rubra rubra (30%) + Festuca arundinacea (30%)], Vicia villosa R., and Trifolium meneghinianum were used as the cover crops. The experiment was conducted in a randomized complete blocks design with four replications including a mechanically cultivated and herbicide treated control plots. The greatest mean persimmon yield (16.2 Mg·ha-1) was observed in the Vicia villosa treatment and the lowest mean yield (3.6 Mg·ha-1) was observed in the bare control. The cover crops increased soil hydraulic properties, with increased aggregate stability, total porosity, reduced bulk density, and penetration resistance. The greatest increases in organic matter contents at 0-20 cm soil depth in the persimmon orchard were observed in the Vicia treatments (73.4% in the first and 74.5% in the second year). The highest aggregate stability (67.4%) and total porosity (60.9%) values were obtained on the Vicia treatments. To increase persimmon yield and improve soil physical and hydraulic properties, cover crops, especially Vicia villosa and Trifolium repens are suggested for clay soils.

摘要：本研究评估了覆盖作物（cover crops）对土耳其某柿园产量及土壤水力特性的影响。研究采集了0~20 cm与20~40 cm土层的土壤样品，针对供试黏质土壤剖面，测定了样品的田间持水量（field capacity）、永久萎蔫点（permanent wilting point）、有效持水量（available water capacity）及饱和导水率（saturated hydraulic conductivity）。供试覆盖作物包括紫羊茅原亚种（Festuca rubra subsp. rubra）、白三叶（Trifolium repens）、高羊茅（Festuca arundinacea）、三者混合配比组[白三叶（40%）+紫羊茅原亚种（30%）+高羊茅（30%）]、长柔毛野豌豆（Vicia villosa R.）及梅氏车轴草（Trifolium meneghinianum）。本试验采用完全随机区组设计，设置4次重复，对照处理为采用机械耕作并喷施除草剂的裸地小区。结果显示，长柔毛野豌豆处理组的柿平均产量最高，达16.2 Mg·ha⁻¹，裸地对照的平均产量最低，仅为3.6 Mg·ha⁻¹。覆盖作物可改善土壤水力特性，具体表现为团聚体稳定性提升、总孔隙度增加、容重降低与穿透阻力减小。在0~20 cm土层，柿园土壤有机质含量提升最显著的为长柔毛野豌豆处理组，第一年提升73.4%，第二年提升74.5%；该处理组的团聚体稳定性（67.4%）与总孔隙度（60.9%）亦为所有处理中最高。综上，为提升柿产量并改善土壤物理及水力特性，建议在黏质土壤中施用覆盖作物，尤以长柔毛野豌豆与白三叶为佳。