Growth and water consumption of jujube with water-saving pruning in deep dried soil of Loess Hilly Area

Abstract: Soil dried layers occur widely in years of trees plantation in orchards. It is important to study soil water restoration condition after tree cutting and effects of dried layers on subsequent vegetation construction and growth. This study aimed to investigate the growth and water consumption of jujube with water-saving pruning in deep dry soil of Loess Hilly Area. The study area was in Jujube Demonstration Base in Mizhi county, Shaanxi province (37°12′N, 109°28′E). The experiment plot had the silt sandy loam with bulk density of 1.24 g/cm3, field water holding capacity of 22% and groundwater depth of 50 m below. In 2011, 5 sampling sites (treatments) were designed. In the sampling site I (experiment plot), 23-yr apple trees were cleared and the jujube with water-saving pruning was planted in soil with dried layers after 4 years; In the sampling site II (CK1), 23-yr apple trees were cleared and the jujube with traditional pruning was planted in soil with dried layers after 4 years; In the sampling site III (CK2), the jujube with traditional dwarf pruning was planted in soil without dried layers; In the sampling site IV (15-yr jujube), the 15-yr jujube with traditional dwarf pruning in soil without dried layers was selected for soil moisture measurement; In the sampling site V (farmland), the farmlands without dried layers for soybean and millet cultivation was selected for soil moisture measurement. Soil moisture in 1 000 cm depth was determined by neutron probes. The jujube yield was determined. The 1-m soil water storage and water consumption were calculated. Available water content, remainder available water and proportion of available water consumption were calculated for orchard soil after cutting, 3-yr jujube soil, 4-yr jujube soil and 5-yr jujube soil. The results showed that 23 years of apple planting had caused soil dried layers in 0-1 000 cm depth. Among the depth, the soil was in the condition of moderate heavy water deficit, moderate water deficit and minor water deficit for 300-500, 500-700 and 700-1 000 cm, respectively. After 4 years of orchard cutting, the soil moisture was recovered in 0-300 cm and the soil moisture in 0-250 cm was almost consistent with the farmland. For the jujube planting after 4-yr of orchard cutting, the soil available water content was 149.71 mm. For the first 3 years, the jujube could growth well but the soil available water in 0-300 cm could be consumed by 34.97%. For the 4th year, the soil available water in 0-300 cm was nearly used up and the jujube had to depend on the precipitation in the same year. In the soil with deep dried layers in 0-1 000 cm, jujube with water-saving pruning could growth well with the yield more than 1.39 times and the yield water use efficiency up to 1.52 times of that with traditional pruning, respectively. The result indicates that the water-saving pruning is an effective way to overcome precipitation shortage and soil water deficit in semi-arid area.