JPH02238824A - Agricultural plastic film - Google Patents

Abstract

PURPOSE:To obtain the subject film, which is a film, having effects on weed control and a rise in ground temperature, provided with a dark color and capable of exhibiting effects similar to those of black films in the initial period of use by coloring the film with a colorant providing colorless transparency with the passage of time after starting the use thereof. CONSTITUTION:The objective plastic film which is preferably a vinylic synthetic resin, such as polyvinyl chloride or polyvinyl acetate, or polyolefinic synthetic resin, such as polyethylene or polypropylene, provided with a dark color and having weed controlling effects similar to those of normal black films colored to black with carbon black and capable of exhibiting characteristics of minimizing a rise of ground temperature in the initial period of use and colored with a colorant fading and providing nearly colorless transparency by exposure to sunrays during use of the film laid on farmland for 1 to several months as a mulching.

Description

Detailed Description of the Invention (a) Industrial Application Field The present invention relates to an agricultural plastic film, and particularly when used as a mulching film to cover the surface of field soil, the film resembles a black film at the initial stage of use. This relates to an agricultural plastic film that gradually fades and becomes almost colorless or light-colored and transparent as it is used for a certain period of time, and that can produce a transparent mulching effect for the purpose of raising and maintaining soil temperature. ) Conventional technology Recently, various types of plastic films have been used as agricultural materials, and they are used in various ways. One of its uses is called mulching, which is a method of spreading plastic film directly onto the surface of field soil.

Since ancient times, a farming method called ``shikiwara'' has been practiced in which rice straw, wheat straw, grass, etc. are spread over the surface of the field soil, and it has been widely used as a standard farming method. The effects of this "Shikiwara method" are as follows.

(1) Prevent soil splashes caused by raindrops from adhering to the lower leaves of crops and contaminating them, and prevent pathogens from entering the soil.

(2) Prevent plowed field soil from becoming hard in a short period of time due to repeated rain and sunshine.

(3) Blocking sunlight from reaching the surface of the field and suppressing the growth of weeds.

(4) Preventing the soil temperature from becoming more than necessary due to sunlight shining directly onto the surface of the field during high temperatures in summer. In particular, hollow straw such as rice straw and wheat straw has a great effect on suppressing the rise in soil temperature.

(5) Preventing moisture evaporation from field soil during dry weather.

On the other hand, the disadvantage of the ``straw method'' is that it prevents soil temperature from rising, which significantly delays crop growth, especially during low-temperature seasons. Another disadvantage of using natural materials is that the work requires a lot of effort.

On the other hand, the ``Bori-Multi method'', in which plastic film is spread directly onto the field soil, has both the same functions and effects as the ``mulch'' method, and the opposite aspect. In other words, <the aspect in which the actions and effects of both are exactly the same>
- Prevents field soil from bouncing back due to raindrops.

- Prevents field soil from solidifying due to repeated rain and shine - Only black or dark colored poly mulch has a weed suppressing effect.

- Prevents water evaporation and drying of field soil during dry weather.

<The functions and effects of both are completely opposite> - In the case of transparent or light-colored poly mulch, it increases the soil temperature and retains moisture, promoting weed growth and growth, and has no weed suppressing effect.

・Natural "straw" always suppresses the rise in soil temperature, but poly mulch, whether black, other colors, or transparent, always lowers the temperature of the ground compared to bare soil where no poly mulch is used at all. Soil temperature increases. In this case, the degree of soil temperature rise is approximately as follows.

Transparent = light color > dark color > black As an example, according to a report from the Saitama Prefecture Horticultural Experiment Station in 1975, the highest soil temperature at 5 cm below the ground surface on August 28 of the same year (weather: clear) between 2:00 and 3:00 p.m. The different temperatures reached are shown in the table below.

(Material name) (Achieved temperature) Transparent polyethylene 36.7℃ White polyethylene
34.6℃ aluminum powder kneaded polyethylene 34.
1℃ black polyethylene 33.8℃ aluminum vapor deposited polyethylene 31.5℃ aluminum foil
30.7℃ without multi-film 29
．． At present, transparent polyethylene and black polyethylene films are used as polyethylene mulch films, with the exception of some special white and silver films.

The main difference between the two is that black poly mulch film is used primarily to suppress weeds during the hot summer season when there is no need for an increase in soil temperature, while transparent poly mulch film is used to increase soil temperature to promote crop growth. The purpose is to maintain soil temperature during the cold season when it is necessary. In the cold season, weed growth is extremely slow, so there is no need to take weed suppression effects into consideration. Of course, in addition to the above purpose, it also prevents mud from splashing due to raindrops.
Naturally, the purpose of use is to take advantage of the general advantages of polymulch films, such as preventing assimilation of field soil and preventing moisture evaporation.

However, crops are not necessarily planted during the high-temperature season and harvested within the high-temperature period.

For example, fall melons are planted in the high temperature period of August and harvested in December or January, lettuce is also planted in August and harvested in January of the following year, and lettuce is planted in early September and harvested from the end of the year until early spring of the following year. There are many crops, such as strawberries, whose cultivation period begins during the hottest period of the year and ends during the lowest temperature.

In all of these cases, poly mulch film is used, but almost all farmers use black poly mulch film colored with carbon black to suppress weeds and keep soil temperature rise to a minimum during the high temperatures at the beginning of planting. They are kept covered with black mulch film until the end of cultivation in winter. Therefore, even in the cold season after the middle of cultivation when it is necessary to raise the soil temperature, the increase in soil temperature remains very small because the black poly mulch film blocks sunlight.

This case is an example where the main purpose of mulching was to suppress weeds during early high temperatures, but the rise in soil temperature during the most important harvest period was sacrificed.

(c) Problems to be solved by the present invention The present invention uses a black poly mulch film mainly for the above-mentioned weed-suppressing effect, or uses a transparent poly mulch film mainly for the purpose of increasing soil temperature during the cold winter season. This was invented to solve the problem of having to make a decision between the two, and not being able to take advantage of the two-pronged effects of poly-mulch film: weed suppression and raising soil temperature. In other words, it exhibits the same weed-suppressing effect as black polyethylene mulch film in the high temperature season at the beginning of cultivation, and as time passes, it fades due to solar ultraviolet rays and becomes colorless or transparent, or almost colorless, and in the cold season from the middle of cultivation onwards. The purpose of the present invention is to provide an agricultural polyolefin film that exhibits the effect of raising soil temperature as a transparent mulch film.

(2) Means for Solving the Problems The present invention is a darkly colored film that has the same weed suppressing effect as the conventional black poly mulch film colored with carbon black at the initial stage of use. With the passage of time, the color gradually fades due to solar ultraviolet rays and finally becomes almost transparent, and from the middle of the cultivation period onward, the variable color agricultural polyolefin film is useful for raising soil temperature in the same way as ordinary transparent poly mulch films.

Here, as pigments that can be expected to have effects similar to those of carbon black, the following may be used alone or in combination with the three primary colors of blue, yellow, and red to produce a color close to black.

For example, the pigment used is red pigment TET49565.
(manufactured by Toyo Ink Manufacturing), blue pigment TETO 1 52
4 (Toyo Ink Manufacturing■&!), yellow pigment TET295
86 (manufactured by Toyo Ink Seisakusho) etc. The above-mentioned coloring pigments are listed as examples, and it goes without saying that other compounds can be used as long as they do not depart from the spirit of the present invention.

In addition, the higher the concentration of the pigment used, the more the effect is similar to the black of carbon black.

In addition, there are differences in weed-suppressing effects depending on the color, but when using a single color, yellow has a weed-suppressing effect to some extent, and in general, a mixture of multiple colors is more effective. The formulation and production method of the colored film for mulch used in the experimental examples of the present invention to be described later are as follows.

Sample NQ1. Red low-density polyethylene: Petrocene #18o (manufactured by Tosoh ■) 100.0 Red pigment: TET49565 (manufactured by Toyo Ink Manufacturing ■) 5.0 Sample Nα2. Blue low density polyethylene: Same as above 100.0 Blue pigment:
TETO1524 (manufactured by Toyo Ink Manufacturing ■) 5.0 Sample Nα3. Yellow low density polyethylene: Same as above 100.0 Yellow pigment:
TE729586 (manufactured by Toyo Ink Manufacturing ■) 5.0 Sample Nα4. Green low density polyethylene: Same as above 100.0 Blue pigment:
TETO 1 524 (manufactured by Toyo Ink Manufacturing ■) 5.0 Yellow pigment: TET29586 (manufactured by Toyo Ink Manufacturing ■) 5.0 Sample Nα5. Dark brown low density polyethylene: Same as above 100.0 Red pigment:
TET49565 (manufactured by Toyo Ink Manufacturing ■) 5.0 Blue pigment: TETO 1524 (manufactured by Toyo Ink Manufacturing ■) 5.0 Yellow pigment: TET29586 (manufactured by Toyo Ink Manufacturing ■) 5.0 Sample Nap. Purple low-density polyethylene 2 Same as above 100.0 Red pigment:
TET49565 (manufactured by Toyo Ink Manufacturing ■) 6.0 Blue pigment: TETO 1 524 (manufactured by Toyo Ink Manufacturing ■) 4.0 Sample Nα7. Black low-density polyethylene 2 Same as above 100.0 Carbon black pigment: TETO 1 530 (manufactured by Toyo Ink Manufacturing ■) 5.0 Sample Na8. Colorless and transparent low-density polyethylene 2 Same as above 100.0 Experimental example in which a film with a width of 100 cm and a thickness of 25 μm was made using an inflation extruder with a screw diameter of 50 mm for each of the above formulations l. Weed control effect When weeds were already beginning to grow in a field covered with the test film in July and August, the period when weeds were most prolific during the warmest season, the grass growth status was as follows. Ta. Sample NQ8 Transparent: Grass grows vigorously and pushes up the film.

Sample hJa7 black: The population gradually declines and all die within 10 to 14 days after the start of the test.

Sample lIlkI6 purple, Nl15 dark brown: almost the same tendency as black. It takes several days for it to die.

Samples Nα4 green, N(13 yellow): The time to wither is longer than samples Na6 and Yang 5, but the leaf tips turn yellow and growth stops in about 10 days. Samples Na2 blue, Nal red: Growth is inhibited. However, it does not reach the point where it withers and dies.

Based on the results of this experimental example, the weed-suppressing effect of materials other than carbon black is that dark brown and purple colors, which naturally have poor sunlight penetration, are better when used in combination with multiple colors.

Furthermore, as a single color, the yellow film had a considerable weed-suppressing effect. Experimental example 2. Effect on soil temperature rise Cover a certain area of the field surface with each test film, stick a thermometer into the center of the film, measure the rise in temperature 10 cm into the soil at fixed intervals, and plot the elapsed time on the horizontal axis and temperature. The elevation was plotted on a graph paper with the vertical axis, and the total calories of solar heat absorbed into the soil was calculated from the area. The value of the bare ground control area without poly mulch film is set as 100,
The value of each test sample is expressed as an index as follows. The measurements were conducted from 10 a.m. to 5 p.m. on July 28th.

Control (without mulch) Sample Nc8 Colorless transparent sample Na7 Black sample Nll6 Purple sample Positive 5 Dark brown 196 sample Nα4
Green 212 samples Nl13 Yellow
228 samples positive 2 blue 220
Sample Nllll Red 235 Based on the results of the experiment, the ones that had a small rise in soil temperature and were close to black films were dark brown and purple.

Experimental example 3. Degree of discoloration of the film due to sunlight: Each test sample was placed directly on the surface of the field, and discoloration due to direct sunlight was observed. The test was conducted from August to October.

Sample NQ7 black: No fading for 3 months.

Sample Na6 purple: Redness almost disappears after 45 days,
It becomes a pale blue color, and after 60 days it becomes a transparent film with a slight bluish tinge. Sample Nα5 dark brown: After 45 days, the redness almost disappears and the color becomes dark green, after 60 days the color becomes even lighter, and after 90 days it becomes pale green.

Sample Nα4 green was not tested.

Sample Nll3 Yellow: Yellow fades continuously, 9
After 0 days, it becomes slightly yellowish and transparent.

Sample Nα2 blue color becomes a transparent film with a slight bluish tinge after 60 days.

Sample Nal red: The color fades considerably in 15 days and becomes almost colorless and transparent after 30 days. (Of course, when red pigment is used alone, more ultraviolet rays enter the film than when it is used in combination with other colors, and the color fades faster.) Experimental Example 4. Effect of increasing soil temperature after the colored film has completed fading In the above Experimental Examples 1 to 3, the weed suppressing effect and the degree of increasing soil temperature were similar to that of ordinary black poly mulch film, and the samples had a small amount of dryness. The Na5 dark brown films were exposed to sunlight for 60 days and 75 days to fade, respectively. The film thus obtained was transparent with a slight bluish tinge.

These two types of fading treated films were compared with a normal colorless transparent film (sample Nα8) and a black film (sample Nct7) according to Experimental Example 2, and the rise in soil temperature was measured. This experiment was conducted in December during the cold season.

The results are shown in the table below.

(Type) (Soil temperature rise index) Sample N
α8 colorless transparent film 199 samples Na7 black film ] 56 samples Film sample Nα6 faded for 75 days Film sample Nα5 faded for 60 days Control group (no mulch) ] 00 (e) Effect of the invention Test sample of the present invention The ridges of the field were covered with an agricultural polyethylene film (width: 12 OCT 1% thickness: 20 μm) made with the same formulation as NQ5 purple, and applied to lettuce planted in August. As a control, ordinary black Borimulti (corresponding to test sample Nc7) colored with carbon black was used.

During the weed growth season in August and September, both the test plot and the control plot exhibited sufficient weed suppression effects, and no damage such as root burn due to excessive rise in soil temperature occurred in either plot. Furthermore, during the season when temperatures dropped from October onwards, the color faded to a nearly colorless and transparent state, and the maximum soil temperature in the test plot remained 2°C higher than the black mulch control plot. In addition, the final yield of superior products was 17% higher in the test plot than in the control plot.

Patent applicant Nikka Kasei Co., Ltd. Hyuga Agrochemical Seed Co., Ltd.

Claims (3)

[Claims] (1) At the initial stage of use, it has the same weed-suppressing effect as a regular black film colored black with carbon black.
It is a darkly colored film that has the property of minimizing the rise in soil temperature, and when used as mulch on a field for one to several months, it fades due to sunlight exposure and becomes almost colorless. Agricultural plastic film colored with a coloring agent to make it transparent. (2) The agricultural plastic film according to claim 1, wherein the film is a vinyl-based synthetic resin such as vinyl chloride or vinyl acetate, or a polyolefin-based synthetic resin such as polyethylene or polypropylene. (3) Claim 1: The coloring agent for dark coloring is one of the three primary colors of blue, red, and yellow, used alone or in an appropriate mixture.
Or the agricultural plastic film described in 2.