Dual effect of fruit tree cultivation on soil physical characteristics

Abstract

Soil bulk density, hardness, moisture and surface soil aggregation composition were measured in 10-, 10~20and 20-year-old orchards in Weibei Region. The results showed that soil bulk density in the 0~30 cm soil layer decreased with increasing orchard age. However, bulk density below the 30 cm layer increased with increasing orchard age, exceeding the 1.30 g?cm?3 upper limit for healthy garden soils. Soil bulk density in the 10~30 cm soil layer was lower in orchards than in croplands. Soil hardness increased sharply below the 30 cm soil layer, almost reaching the 1 000 kPa upper limit of soil quality standard for healthy root growth. Soil hardness in the 17.5~27.5 cm soil layer is lower in orchards than in croplands. Soil aggregation status was poor in surface soil of orchards. Most water-stable aggregates in the orchard soils were in 0.5~0.25 mm range class. Contents of water-stable soil aggregates 0.25 mm increased with increasing age of orchards. Water-stable soil aggregates contents in 20-year-old orchards were two times higher than those in 10-year-old orchards. Fruit trees have a dual effect on soil physical characteristics. Soil physical conditions was generally improved in topsoil (0~30 cm), but worsen in subsoil (30 cm) with increasing orchard age. As latent degradation of subsoil in orchards affected the healthy growth of fruit trees, any such degradation should be carefully monitored.