Wind erosion prevention effect of suspending shoots on wires after winter pruning in soil-burying zones over-wintering

Abstract: Ninety percent of Chinese viticulture regions are distributed in soil-burying over-wintering zones. Traditional viticulture management causes soil surface to be exposed for about 6 months per year during the cold winter and the dry windy spring when there is almost no rain but strong wind. Large area of bare soil, which comes from grape soil-burying over-wintering, results in increasing risks of wind erosion in viticulture regions. In order to reduce this erosion, a new training system called crawled cordon training (CCT) is used in the experiment. CCT has one horizontal cordon which is above the soil surface, and vertical shoots are distributed equally on cordon of the first wire and tied. Vines are trained to the regular canopy during the growth period, and the shoots of vines on the wires after pruning in winter form a kind of windbreak and play a protective role as shelterbelt network. The experiments studied the degree of porosity of shoot windbreak and the windbreak potency according to typical farmland shelterbelts. Additionally, the experiments evaluated the relationship between wind speed and shoot windbreak, as well as sediment discharge and the different heights. The results showed that: 1) Digital image processing was used to get the porosity of shoot windbreak, which followed normal distribution, and 75.6% of the values were between 0.48 and 0.68, and the mean was 0.58. Therefore, it was considered as a ventilating structure. 2) The wind speed reduced by 61.90% on the edge of windward side. On the basis of the relationship between the protection length and wind speed, the wind speed changed differently: slack by resistance (from the distance of 10 m from the windward of the windbreak to the edge of the windbreak), collect and accelerate (10 m from the edge of the windward within the windbreak), weaken speedily (24-34 m from the edge of the windward within the windbreak), renew again (from 48 m from the edge of the windward to the edge of the leeward within the windbreak), slack in leeward side (from the edge of the leeward to 34 m from the edge of the leeward). At 34 m from the edge of the windbreak on the windward side, there was the lowest wind speed, which reduced by 84.20% compared to the open field, and the effect of wind prevention was 80.72%. The average wind speed in the shoot windbreak reduced by 40.96% compared to the open field. 3) The effects of wind prevention had significant difference in different regions, and the mean was 34.95%. The results showed that the average wind speeds at 3 sites (10 and 24 m far away from the edge of the windbreak on the windward, and the edge of the windbreak on the leeward) were higher than the open field. The length which was less than 34 m from the leeward side belonged to the relative effective protection length, and the mean effect of wind prevention was 40.94%. 4) This research established the relationship between the sediment discharge and different heights in the vineyard (with shoot windbreak or without shoot windbreak), and it followed power function. The total sediment discharge of the vineyard which had shoot windbreak was 39.0 % higher than the control. All sediments centralized near the ground. 46.73% of all sediments of the vineyard which had shoot windbreak centralized at the height of 5-50 cm, and 41.96% for no shoots. The sediment discharge decreased with the height increasing. With the development of the viticulture managements, the exposed areas of soil surface are expanding, and the risks of wind erosion would be increased. Some measures must be taken to reduce the degree of wind erosion. Therefore, the results in this paper provide a reference for the wind prevention and the reduction of wind erosion.