黄土丘陵区深层干化土壤中节水型修剪枣树生长及耗水

黄土丘陵区人工林地深层土壤干层是否影响后续植物的生长是众多学者关心的热点。该文在砍伐23 a生旱作山地苹果园地后休闲4 a又栽植枣树,连续3 a观测干化土壤中枣树的生长及土壤水分变化,研究采用节水型修剪的再植枣林的生长及耗水情况。结果表明,前期23 a生苹果园地已使0~1 000 cm深土壤干化,休闲4 a后0~300 cm土层水分得到恢复,300~500 cm范围为中度偏重亏缺,500~700 cm为中度亏缺,700~1 000 cm为轻度亏缺;3龄枣树时开始采取节水型修剪,0~300 cm土层有效水分被消耗34.97%,至4龄时0~300 cm范围内前期恢复的土壤水分已消耗殆尽;在此情况下采取节水型修剪的枣树仍可保持良好生长,产量及其水分利用效率均高于相同水分条件下的常规修剪枣树,产量可达正常水分条件下枣树的1.39倍以上,产量水分利用效率可达1.52倍以上。研究结果证明节水型修剪是半干旱区深层干化土壤中枣树克服雨量不足和土壤水分亏缺的一条有效途径。

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

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 1000 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 0-1000 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 700-1000 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 0-1000 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.