Root Distribution Of Jujube And Influence Of Root Zone Water Control In The Hilly Densely Plantation

Jujube is one of the characteristics fruit in loess hilly and semiarid areas. In recent years, the planting model of high-efficiency water use in hilly dense planted jujube trees make great achievements by means of mountain rainwater-collecting micro-irrigation and dwarf dense planted technology, Irrigation quantity decreased 84.4%, while the average output increased 46.7% compared with traditional furrow irrigation. It can change jujube tree root zone water environment, affect root distribution and promote water and nutrient absorption. Thus, it has the important significance in the study of water control compared with the root distribution for revealing the increasing production mechanism and water and nutrient high-efficiency management. But few studies focus on the influence of root zone water control on root distribution.This paper investigates the spatial root distribution of different jujube tree age, analyzes the influence of different water control on the root spatial distribution and the growth based on trench profile method and soil core method, determine the effects of water control on jujube tree root distribution in the loess hilly and semiarid area. Results can provide the basis for jujube tree high-efficiency operation and sustainable development.The main research results are as follows:(1) We improve traditional root uncovering methods and Proposing a novel and more efficient method which is steel brush plus water-spraying.The higher number of roots were exposed by the steel brush strike third time plus water-spraying method, which uncovered 9.2%, 375%, 187.9%,126.2 % and 46.2% of total roots, and 8.9%, 345%, 180%, 117.8% and 44.1% of fine roots exposed by steel brush strike without water-spraying, polishing, polishing plus water-spraying, roughening, roughening plus water-spraying and, respectively.(2) There is a statistical significant difference in total root vertical distribution while vi Root distribution of jujube and influence of root zone water control in the hilly densely plantation no statistical difference in fine root horizontal distribution of different densely planted jujube tree age.Spatial distribution of the roots in densely planted one-year-old, four-year-old, eight-year-old and eleven-year-old jujube trees was investigated using a trench-profile method. Result shows that root number increased with tree age. 85.7% of the coarse root ( 3mm) number and 54.0% of the medium root (l-3mm) number was located in the 0-20cm soil depth layer in one-year-old jujube tree, and 69.2% of the fine root ( lmm) number was located in the 0-40cm soil depth layer. Whist root including coarse root, medium root and fine root of other three year old tree are mostly located in the 0-60cm soil depth layer. There is statistical difference in horizontal distribution of mediun and coarse root number in the 0-100cm soil depth layer, but no of fine root. And, there is no statistical difference in horizontal distribution of different diameter root number in the same soil depth layer between one-year-old jujube plantation with 120cm tree spacing and other three tree ages with 200cm tree spacing.(3) There is a statistical significant difference in root zone water control on densely planted jujube tree spatial root distribution, but the effect is different.The methodology developed to study 8-year-old densely planted jujube trees root distribution was based on the trench-profile method. This study included four treatments: sloping land (Wl), sloping land plus drip-irrigation (W2), mini-catchments (W3), and drip-irrigation plus mini-catchments (W4). Overall in the four treatments, W2, W3 and W4 can promote root growth and enrichment significantly on the one hand, and on the other hand decrease the maximum rooting depth. Rankings for the total root density influenced on the root zone water control is W4 W2 W3 Wl. Approximately 60% of the fine root number was in the 0-40cm soil depth layer, and 80% of the root number was located in the 0-60cm. And 69% of the fine roots were concentrated under the drip irrigation soaked area or inside the mini-catchment. The order for the maximum root depth is Wl (8m) W3 (5m) W2= W4 (4m). Root zone water regulation practices increased a tendency to more uniform and widely distributed fine roots in the upper soil layers which will absorb more water from upper layers, and therefore require less from deeper layers. So, downward root extension and water depletion in deeper soil layer will be reduced through an increase in the soil water content of upper soil layers. Furthermore, this will avoid the formation of dry soil layers.(4) Water control method in different drip-irrigation location promote root growth The growth discipline of fine roots, including the whole profile (0-100cm depth) at different distances 35cm, 65cm and 100cm from the trunk respectively was studied based on the soil core method. Results shows that in the non-irrigated soaked area, rankings for the values of root dry weight, root length and root surface was 35cm 100cm 65cm, root day weight density was 512.5g/m~3, 368.6g/m~3 and 288.3g/m~3 respectively, root length was 2099.4cm, 1748.3cm and 1664.4cm respectively, root surface area was 256.1cm~2, 201.2cm~2 and 155.2cm~2.Compared with the non-irrigated soaked area, root dry weight density increased by 28.3% 58.8% and 35.9% respectively, root length increased by 29.7%, 26.1% and 34.0% respectively, root surface area increased by 5.4%, 28.5% andl4.6% respectively in 35cm, 65cm and 100cm away from the trunk. Drip irrigation water control can promote fine root growth in any location in jujube plantation.