Evaluation of the effect of biodegradable plastic film
1. Initial evaluation
Compared with ordinary PE mulch film, in addition to the degradation characteristics, other mechanical performance indicators such as tensile strength, elongation at break, right-angle tear strength, dart impact strength, etc. must also be the same as those of ordinary PE mulch film.
2. Process evaluation
(1) Degradation rate
From covering to complete disappearance, biodegradable plastic film has to go through several stages of character change. Referring to the opinions of Zhang Zhenhe, chief expert of the National Agricultural Technology Extension Service Center, the degradation cycle can be divided into the following stages: induction period, rupture period (cracking period), large cracking period (disintegration period), fragmentation period (complete disintegration period) and film-free period (complete degradation period). The criteria for determining the degradation stage are shown in Table 1.
The degradation stage of plastic film can vividly reflect the degradation rate of plastic film, and also directly affects the growth process of crops. Therefore, these degradation periods are one of the most valuable indicators for evaluating the effect of plastic film. The degradation rate of mulch film should be consistent with the requirements of crops for the degradation stage. If the deviation is too large, that is, too fast or too slow degradation may cause yield reduction.
(2) Warming up
When using the degradable plastic film, record the temperature change of the soil at a depth of 0-25 cm, and compare it with the situation of using the PE plastic film to calculate the effective accumulated temperature to meet the growth needs of crops.
(3) Moisture retention
The biggest challenge of degrading plastic film is the improvement of moisture retention. In the arid regions of the northwest, the requirements for the moisture retention of plastic film are very high, especially in the early stage of seedling breeding, moisture protection is more critical. Therefore, how to improve its moisture retention requires everyone to improve it together.
(4) Others
Degradable materials can also be used for mulch films for special purposes or special functions, such as colored mulch, perforated mulch, chemical weeding mulch, and water-permeable mulch.
3. Result evaluation
(1) Production situation
After the widespread use of mulch, the use of degradable mulch, the crop yield is meaningless compared with not covered with mulch, and can only be compared with traditional mulch, whether there is a reduction in yield. The ultimate purpose of promoting degradable plastic film is not only to solve the pollution problem of ordinary plastic film, but more importantly, to ensure that the yield of crops is increased or not reduced.
(2)Degradation effect
