关键词: 飞机播种, 榆林沙区, 适宜播期, 种子发芽, 起沙风, 人工播种, 播量, 沙丘链, 样地, 温度条件

Abstract: The sellcction of air seeding season depends on mainly the close sequence of rainfall and the sand-blowing wind, and wind erosion-resistant seedlings is considered as main plant for cultivating. In May, the southeast and northwest winds alternate more frequently, and this is favourable to the covering of seeds by sand. In early June, the frequence of the sand-blowing wind is obviously reduced, so it is unfavourable to the covering of seeds by sand. The continuous rainfall of 20 mm or so indispensable to the germination of seeds covered by sand is concentrated mainly in the period after the second decade of June. However, seedlings emerging after rainfall in the first and second decades of July are still more resistant to wind erosion, whereas seedlings emerging after the rainfall in the third decade of July will be greatly weakened in their resistance of wind erosion. On the basis of above-mentioned analysis, the auther puts forward the suggestion that the air seeding of Hedysarum fruticosum var. leave and H. scoparium should be conducted during the first decade of May to the first decade of June, more available of the second and third decades of May to realize this practice.