(1) Select seeds. Production practice has proved that selecting seeds is an effective measure to cultivate early, neat and strong seedlings. Seeds for sowing shall be selected and screened by wind to remove shriveled seeds, tender seeds and impurities. Seeds with full, high 1000 grain weight, uniform size, fresh color and high germination rate shall be selected as seeds, so as to meet the requirements of improving the emergence rate and making the whole seedling strong. According to the survey, if the seeds with poor maturity or low 1000 grain weight are used for sowing, the germination rate will be reduced by 20% - 25%, the emergence will be uneven, the seedlings will be thin and weak, vulnerable to diseases and pests, and the small hemp rate will be high. Sowing with the old seeds of the next year (the seed coat is dark green) will greatly reduce the germination rate and cause serious seedling shortage and ridge cutting.
(2) Determine the appropriate sowing date. Hemp seeds can germinate at low temperature (1-3 ℃), and their seedlings have the ability to endure short-term low temperature. Therefore, the range of sowing date in each hemp area is relatively large. Judging from the sowing date of marijuana in different places, there are great differences due to different climate, soil, varieties and rotation systems. Liaoning sows in the first ten days of April, Jilin and Heilongjiang sows in the middle and last ten days of April to the first ten days of May. The sandy loam in machou, Hebei Province was sown from late April to early May, while the wet and cool lower tidal land or clay loam was sown until late May. Spring hemp was sown from late March to early April in Tai'an hemp District, Shandong Province. Summer hemp is sown in early June.
The sowing date of cannabis is related to different cultivation and utilization purposes. During hemp picking and cultivation, it is generally timely and early sowing; For seed collection and cultivation, in order to make the mature stage of seed irrigation slurry in the cold climate in autumn, it is generally sown late. The sowing date should also coincide with the local retting water temperature during harvest. Hemp is sown when the soil temperature rises above 8-10 ℃ in 5-10cm, and it takes 10-15 days from sowing to emergence. In this case, sowing as soon as possible, long seedling period and deep root system can play the role of cultivating strong seedlings. Miao Zhuang laid the foundation for rapid growth, accelerated the growth of hemp plants, orderly hemp field population, increased the number of effective plants, improved the yield of hemp and increased the fiber yield. Early sowing, fast growth and timely and early harvest. Retting hemp with warmer water temperature can achieve the effect of high yield, high quality and high economic benefit. Therefore, for the timely and early sowing of hemp, we should not only pay attention to the ground temperature at the time of sowing and the temperature in the rapid growth period (19-23 ℃), but also take into account the water temperature required during retting (above 20 ℃). Only when the three are well combined can we achieve a comprehensive effect.
(3) Sowing method. There are three sowing methods of marijuana in various places: sowing, drill sowing and on-demand sowing. Seed collection and cultivation are commonly used for on-demand sowing, drill sowing and sowing. Hemp picking and cultivation are multi-purpose sowing and drilling. Hemp for fiber is suitable for close planting, and drill planting should be used in large-area cultivation. Drill sowing has the advantages of uniform seed setting, consistent sowing depth, neat emergence, convenient field management and so on. The row spacing of mechanical drill sowing is 12.5cm-15cm, the row spacing of columbine drill sowing is generally about 13cm, and the plant spacing is 5-6cm. The mechanical row spacing of narrow row machine is 7.5cm. According to the test, when 600000 and 1.2 million seedlings are left per hectare, the yield of narrow row machine is 21.2% and 8.7% higher than that of 15cm machine respectively.
(4) Sowing amount and sowing depth. The sowing amount of cannabis varies greatly across China, ranging from 15-105kg per hectare, which varies with varieties, cultivation purposes and sowing methods. The sowing amount of early maturing varieties is more than that of late maturing varieties, the sowing amount of varieties with high 1000 grain weight is more than that of low varieties, the sowing amount of hemp picking cultivation is more than that of seed picking cultivation, and the sowing amount of wide strip sowing is more than that of machine strip sowing or columbine sowing. Hemp seeds have weak top soil force and are suitable for shallow sowing. In the drill sowing area, the sowing depth of 3cm is appropriate, and more than 7cm will seriously affect the excavation of hemp seedlings; It is generally suitable to cover soil for 2cm in the sowing area.