Covering properties of nonwovens for vegetable production


How the coverage of non-woven fabrics will directly affect the growth and yield of vegetables, mainly in the following areas.

1.Light transmittance

The flat coverage method was used to determine the average solar irradiance of the non-woven fabric with the basis weight of 20g / m2 and the light transmittance of 87g at 30g / m2 79%, 72% for 40g / m2 and 73% for 25g / m2. One 25g / m2 of non-woven spunbond production method, the light transmission rate is slightly worse. Nonetheless, these four sizes of nonwovens meet the light exposure requirements of vegetables.

2.Breathability

Non-woven breathable plastic plastic sheeting is superior to, with a certain degree of breathability, without covering after the cover ventilation, labor-saving, the size of the permeability and the size of the non-woven structure of the intermittent, temperature and wind speed inside and outside the cover layer close However, the air permeability and the thermal insulation were negatively correlated, that is, the thermal insulation decreased as the air permeability increased. It has been determined, 20g / m2 of non-woven breathable rate of 5 ~ 6m3 / (m2.h), to meet the needs of vegetable growth.

3. Insulation

Insulation of vegetables on agricultural nonwovens is mainly manifested in the leaf temperature of vegetables, surface temperature and ground temperature have a certain degree of improvement.

(1) Increasing the leaf temperature of vegetables According to the three sunny days in winter and the three cloudy days, the lettuce was covered with 20g / m2 non-woven fabric and exposed to the ground (CK) The average warming value of winter lettuce leaves increased by 0.75 ℃ at the time of 4:00, increased by 0.9 ℃ at 8:00, increased by 3 ℃ at 12:00, increased by 1.6 ℃ at 20:00, 00 when the warming 0.65 ℃, the highest temperature at noon, up to 3 ℃, night cooling stage can still warming 0.65 ~ 0.75 ℃. Obviously, the increase of leaf temperature is very beneficial to the growth of winter production. In actual use, in order to improve the effect of warming at night, the foliage of plants should not stick to the non-woven fabric cover.

(2) The increase of surface temperature, the use of 20g / m2 non-woven directly covered in the winter lettuce, the sunny surface average warming nearly 2 ℃, cloudy at about 1 ℃, especially at night when the low temperature, the effective ground radiation Weakening, thermal insulation better, up to 2.6 ℃, but cloudy insulation effect is only about 50% of sunny night.

(3) In the middle temperature, the warming effect of 20g / m2 agricultural non-woven fabric on winter lettuce was taken as an example to measure the warming effect of soil layers of 5cm, 10cm, 15cm and 20cm with depth of 1.8 ℃ , 1.1 ℃, 1.1 ℃, 0.7 ℃, while the rainy days are lower, respectively 0.8 ℃, 0.7 ℃, 0.4 ℃, 0.3 ℃. The results show that the warming effect of sunny days is obviously higher than that of rainy days, the warming effect of shallow soil layer is higher than that of deep soil layer, and the soil layer affected by warming effect can exceed 20cm. In cold winter, increasing soil temperature is conducive to the absorption of soil moisture and nutrients by the vegetable roots, accelerating and robust root growth, thereby promoting the growth of shoots and shoots above ground and improving the stress resistance of shoots. In winter, the effect of soil temperature increase on crop growth is more important than the increase of ground air temperature, the effect is more obvious.

(4) The comprehensive ability to prevent cold increase temperature on the growth of vegetables, yield a significant impact. The 20g / m2 non-woven fabric covering the cold warming effect is more obvious, in the extreme low temperature (-7.2 ℃) conditions, than the open air temperature increased by 3.8 ℃. According to the information, the ability of short-term low-temperature lettuce seedlings in the -5 ~ 6 ℃, the use of agricultural non-woven fabrics to prevent low temperature capability can reach -9.5 ℃ limit, such as the use of larger quantitative non-woven fabrics or layers Non-woven fabrics stacked together can also be used to further enhance the ability to prevent low temperatures.