USE OF PAPER MULCH IN VEGETABLE PRODUCTION

Mulching with organic materials has been very long and beneficial for plant growth but plastic mulches widely replaced them. However they are not suitable when the consideration is given to environment pollution. Paper mulches are the solution for the environmental problems due use of plastic mulches. Several kinds of paper material have been used for mulching in different vegetable crops. Kraft paper have been used most commonly for mulching. Paper mulches may lower soil temperature as compared to black plastic mulch or bare soil. Oil treatment in paper mulches may improve its capacity to conserve soil moisture. Black paper mulch and black polyethylene mulch can be equally effective in controlling weeds. Paper mulches are less durable as compared to plastic mulches because they get easily destroyed with wind or rain. In future paper mulches with better strength and developing properties for mulching is needed.

Mulching is a very old practice which had been used by farmers and agriculturists since a long time for improving soil conditions by covering the soil surface with different kinds of materials. Plant growth is encouraged in a better way with the improvement of physical environment of the soil. Using mulch on the soil surface adds organic matter to it, reduce weed growth and also checks soil erosion to some extent. Several kinds of mulches had been used to control weeds and to improve plant health. In the ancient times mulching with organic matter was done along with stones, pebbles, gravels, volcanic ash and cinder as well as other lithic materials. These methods not only reduces evaporation but also decreases runoff of upper soil layer by wind or heavy flow of water.

No doubt mulching with organic materials has been very long and beneficial for plant growth but plastic mulches widely replaced them and are very common in vegetable production these days. An ideal mulch should be made up of a renewable material, biodegradable, durable, permeable to rain and huge winds. It should suppress weed growth, maintain soil temperature and moisture and checks evaporation. Also it should be cost effective and easily manageable and should be easy to put in the field. Paper mulches are better option for mulching because they can be easily decomposed and incorporated into the soil whereas plastic mulches have problem of disposal. Although, paper mulches are more expensive than plastic mulches, life span is shorter and can be destroyed easily with heavy rain and wind.

Materials used for paper mulches

Paper is a thin material produced by pressing together moist fibres of cellulose pulp derived from wood, rags orgrasses, and drying them into flexible sheets. It is a versatile material with many uses, including writing, printing, packaging, cleaning, mulching and a number of industrial and construction processes. The function, durability and stability of a paper mulch depends on the selection of quality raw paper material. Quality can be enhanced by constituents like mineral fillers, dry and wet strengthening agents, colorants and water repellents. Several kinds of material have been used for mulching in different vegetable crops. Kraft paper have been used most commonly for mulching. Commercial mulch papers are also available as colored and uncolored. All the paper mulches which are used for mulching and are not covered with polyethylene can be used for mulching in organic farming as these are biodegradable and can be ploughed into soil.

Durability of paper mulch have a direct effect on the degradability of the mulch. It was found that newspaper degraded most rapidly, followed by shredded newspaper and straw mulch was slowest in degradation [1]. The paper started degrading from the sides of the paper and allowed weeds to grow on edges. The major disadvantage of the paper mulch is its degradation from edges. Oil coating can be a solution for the fast degradability of the paper. Also saturated paper mulch with vegetable oil significantly prolongs usage time of mulch. Durability of a paper mulch depends on the quality of paper, soil and weather conditions.

EFFECT OF PAPER MULCH ON SOIL TEMPERATURE

It is a well known fact that mulching can modify the soil temperature in different geographical regions. Paper mulches may lower soil temperature as compared to black plastic mulch or bare soil. This might be due to the less absorbed light by lighter color of the paper than the black plastic film which absorbs more light. In a study the soil temperature was higher under waxed paper mulch than the kraft paper and it was higher in black polyethylene mulch than the paper mulch. Color of the paper mulch had an direct effect on the soil temperature [2]. Treating the paper with oil may increase penetration of thermal radiation which leads to increase in soil temperature. Paper mulches can be used in higher hills for the production of cool season crops as the mulch can increase the soil temperature.

EFFECT OF PAPER MULCH ON SOIL WATER CONTENT

Soil water content depends on soil structure, temperature and evaporation. Mulching can conserve moisture by avoiding evaporation. However, the positive effects of mulching on soil water content depends upon the climate. In temperate regions there is very little effect of mulching on the soil water content under different mulches or bare soil. It was revealed that both biodegradable paper mulch or brown Kraft paper was able to keep soil moisture than the plastic mulch [3]. While effectiveness of polyethylene mulch was shown better than the paper mulch for conserving soil moisture [4]. Oil treatment in paper mulches may improve its capacity to conserve soil moisture. Straw mulch can be very effective in conserving soil moisture for a longer time because it allowed penetration of water and avoided losses due to evaporation.

EFFECT OF PAPER MULCH ON WEEDS

Weeds causes a huge losses to the main crop as they fight for nutrition, water, light etc with the main crop. Mulching can reduce the losses due to weeds and can also save manpower and total cost of production by avoiding mechanical weeding practices. Paper mulches have been found equally or even more effective in controlling weeds than black plastic mulch. It was found that butcher paper and polyethylene coated kraft paper were equally effective in weed control as compared to plastic mulch [2]. In a study on tomato paper mulch was found better to control weeds than black polyethylene or biodegradable plastic mulch [5]. The color of the paper mulch can be very effective in controlling weeds. Black paper mulch and black polyethylene mulch can be equally effective in controlling weeds.

EFFECT OF PAPER MULCH ON YIELD

Mulching with paper may increase yield and can also improve fruit quality as the fruit does not get a direct contact with soil. Also as the weed competition is less and moisture conservation is there so the availability of nutrients is more to the crop and there is increase in yield. For example the yield of head lettuce was significantly higher when paper mulch was used in a warm and dry season [6]. There was increase in yield of tomato when kraft paper, oiled kraft paper and commercially available black paper mulch was used with unmulched treatment [7]. The benefit from different type of mulches also depends upon weather conditions in which they are used. For example paper mulch gave best result in the rainy season as compared to plastic and straw mulch for increasing yield of tomato [8]. Effect of paper mulches on different vegetable crops is given in Table 1.

These days plastic mulches are more economical than all other mulches. However they are not suitable when the consideration is given to environment pollution. The availability of paper and high cost of paper mulch is a major problem for large scale field production of vegetable crops. More extensive use of paper mulches could bring the production price closer to plastics, but hardly to the level to compete with them if only the price of mulch is considered. Paper mulch can be left in the soil after the crop ends without any environmental concerns, so its valued gets increased as compared to plastic mulch particularly in the presence of increased environmental awareness. The major problem with the paper mulches is their durability. Paper mulches are less durable as compared to plastic mulches because they get easily destroyed with wind or rain. Paper mulches with better strength and developing properties for mulching is needed, because many paper products tested so far tend to degrade too fast. Because of the environmental problem caused by the use of plastic mulches, it is not too difficult to forecast that there will be great demand for cheaper better and cheaper paper mulches that are environmentally trouble free.