Mulching: Materials, Advantages and Crop Production

Abstract

Mulching materials in crop production plays a pivotal role in minimizing the weed menace, decreasing dispersion of soil particles by rain drops and containing soil erosion, balance of soil temperature and soil moisture conservation. Mulching materials of organic origin are found to be major stakeholders in more moisture retention in the root zone depth and improved soil physical properties, nutrients supply and enhanced growth, yield and quality of crop and up on decomposition adds organic matter to the soil. Vegetable production is an enterprise demands huge inputs like irrigation water, fertilizers, plant protection chemicals and intercultural operations. Likewise, the establishment of seedlings in the field is a tedious work in scanty rainfall regions which is considered as a dwindling natural resource. In view of advantages by mulching particularly in insulation of soil temperature and moisture conservation in hot arid and semi-arid areas, the practices of mulching in crop production is recommended to reduce the cost of cultivation.

Full text

Mulching: Materials, Advantages and Crop
Production
Pedda Ghouse Peera S.K.*, Subhankar Debnath and Sagar Maitra
Centre for Smart Agriculture, Centurion University of Technology and Management, Odisha-761211
*Corresponding author: ghouse.peera@cutm.ac.in
Abstract
Mulching materials in crop production plays a pivotal role in minimizing the weed
menace, decreasing dispersion of soil particles by rain drops and containing soil erosion,
balance of soil temperature and soil moisture conservation. Mulching materials of organic
origin are found to be major stakeholders in more moisture retention in the root zone
depth and improved soil physical properties, nutrients supply and enhanced growth, yield
and quality of crop and up on decomposition adds organic matter to the soil. Vegetable
production is an enterprise demands huge inputs like irrigation water, fertilizers, plant
protection chemicals and intercultural operations. Likewise, the establishment of seedlings
in the eld is a tedious work in scanty rainfall regions which is considered as a dwindling
natural resource. In view of advantages by mulching particularly in insulation of soil
temperature and moisture conservation in hot arid and semi-arid areas, the practices of
mulching in crop production is recommended to reduce the cost of cultivation.
Keywords: Mulching, organic mulch, synthetic mulch, crop production
1. Introducon
Protected cultivation is one of the revolutionary ways for realizing optimum yields
over a decade amid the challenges like globalization of markets, shrinking cultivable
lands and climate change. This is the technique wherein the microclimate around the
plant is controlled fully or partially to protect the crop from adverse conditions and
presently it is catching up in tropical countries for high value ower and vegetable
cultivation (Maitra et al. 2020). Mulching is one of the potential protected cultivation
approaches to serve this purpose. It is a protective ground cover that can include
manure, saw dust, seaweed, litter, stubbles, sands, pebbles, plastics, and other natural
6
Chapter
Mulching: Materials, Advantages and Crop Production. In: Protected Cultivation and Smart
Agriculture edited by Sagar Maitra, Dinkar J Gaikwad and Tanmoy Shankar © New Delhi Publishers,
New Delhi: 2020, (pp. 55-66). ISBN: 978-81-948993-2-7, DOI: 10.30954/NDP-PCSA.2020.6

56 Protected Cultivation and Smart Agriculture
products. While the term mulching is a practice of covering the surface of soil with
these materials to reduce moisture loss, and to balance wide variations in diurnal soil
temperatures, especially in the root zone. It controls evaporation losses and minimized
energy supply to the evaporating site by cutting off solar radiation falling on the
ground. Major function of mulching is to limit rst stage of drying which helps in
optimum moisture status, reduced soil temperature, also containing seedling mortality
and improving crop stand. It also subdues weed-ora and lessens weed competition
with crop for water and nutrients making them available in larger amounts for crop
plants. In addition, mulching helps in improving downward movement of water.
The efciency of mulches in preserving moisture has usually been established to be
greater under higher rainfall, drought conditions and during vegetative stages of crop
growth when canopy cover remains scanty. This book chapter discusses concisely the
role of mulching materials for cost effective for production of high-value vegetable
crops.
Mulch is used for various purposes:
1. To sustain the fertility of soil.
2. To protect the soil from water and wind erosion.
3. To preserves the soil moisture.
4. To accent landscape plantings.
5. To provide a “nished” look to the garden.
6. To help in production of clean and quality products.
7. To protect the plant and their produce from attack of insect-pest and diseases.
8. To moderate the soil thermal regime throughout the cropping season.
9. To prevent weed growth.
10. Increasing overall crop production
2. Types of mulches
Mulches are basically classied in two types viz., organic and non-organic mulches
(Fig. 1). The important mulching materials essentially used in crop production are
explained below:
2.1. Organic mulches
2.1.1. Compost/Manure/peat
These mulching materials are laid in 2” – 3” thick layer over crop or soil surfaces and
used commonly for attractive appearance. Manure needed be well decomposed before
laying, otherwise they may damage the crops. These type of mulching materials are
generally used for kitchen and home gardens. Besides, mulching these materials will
improve soil fertility through increasing organic carbon status. It is frequently free of

Mulching: Materials, Advantages and Crop Production 57
weed seeds and cost effective. The raw materials for compost or manure are easily
available from commercial producers or homeowners. One can produce compost
from the raw materials available in his yard. There is no compulsion of purchasing
expensive raw materials for mulching.
2.1.2. Crop residue mulching
These mulching materials are easy to handle, thus gaining attention. To make the crop
residues considerable chopping is required. Therefore, these should be applied in thin
layers (only to a 3 inch or less depth) and recommended for drought prone areas.
Moreover, these materials are prone to micro-fauna which make theme desirable for
medium duration crops.
Grass clippings also are very effective mulches and can be used directly from the
lawn mower. These mulching materials need to be applied in thick layers (4 to 6
inches). If the layers are very thick, they hinder the air penetration to the bottom
and may cause smelly rotten material. It such situation it may not useful as soil
conditioner. However, these are the one of the most easily available mulch materials,
undervalued mainly because of people’s experience with smell rotting masses when
clippings are continually dumped in thick layers. It is recommended that not to use
clipping from lawn treated with herbicides.
Fig. 1: Grass clipping and straw mulching in cucurbits cultivation (Source: Oliver 2020)
2.1.3. Sawdust
Partially decomposed sawdust are the important mulch materials which stays for long
time. It contains high amount of carbon and nitrogen and prone to caking. Due to
high C:N ratio and nutrient status it takes time to breakdown. It must not be used
as mulch until its proper decomposition into brown ‘soil’ and worms are found in it.
Softwood sawdust required more time to decompose than hardwoods. To make the
decomposition faster, nitrogen may be added externally to sawdust and spread it two
inches deep on the soil.

58 Protected Cultivation and Smart Agriculture
2.1.4. News paper
Sheets of newspaper are used to cover lightly with grass clippings or other mulch
material to anchor. The main disadvantages of these mulch materials is they are
easily blow away and once get damp are easily broken up or penetrated by weeds.
However, these mulch materials are chlorine-free and there is no risk of lead from the
ink. Details furnished in Table 1.
2.2. Non-organic mulches
2.2.1. Polyethylene mulches
Non-organic mulches generally lack the soil improving properties particularly to
improvement in soil particle aggregation, structure formation and regulation of soil
reactions. Amidst the different inorganic mulch materials, the use of these mulches
is most preferred owing to their properties of regulating the hydrothermal regimes of
microclimate of crops, positive response on weed control, protect soil from dryness
and crusting, control soil moisture by checking evaporation from surface, protect
surface soil from erosion and reduce nutrient loss.
2.2.2. Aluminum-coated plastic and foil
Use of these mulching materials mainly conned to vegetable crops. They also
reduce insect pests, viz., aphids and viruses in vegetable crops. The single layer of
the mulching provides excellent weed control. However, they are very expensive and
quite unpopular.
Fig. 2: Polyethylene cultivation in tuberose cultivation
3. Selecon of organic mulches
Undecomposed or partially decomposed mulch material should not have a
nitrogenase activity after the application of mulch.
Should not have any antagonistic effect on the crop.

Mulching: Materials, Advantages and Crop Production 59
It should be free from the attack of insects/pests particularly termites and
diseases.
Determination of mulch depth and identication of plant for moisture and
oxygen tolerance are the two important steps in organic mulching.
Table 1: Mulching materials and specications for use
Depth Material Comments
1-2 inches Peat Moss Attractive, available but expensive for large scale. Moisture
shall be maintained at all times.
Bark Ground and packaged commercially.
2 inches Peat Soak well before using. Breaks down rapidly
Sawdust Usage of weathered sawdust if mixing with soil. Fresh
sawdust causes N leaching up on break down in soils
2-3 inches Decomposed litter
Grass clippings
Rapid break down and formation of stable aggregates
Maize cobs Gives moderate acidic nature to soils. Excellent for soil
structural stability
Peanut Hulls Improves soil structure, fairly durable. May harbor
nematodes
Shredded Tree
Leaves
Cheaper, act as breeding stations for termites and ants
3-4 inches Hay Unattractive but repeated use adds nutrients which lasts for
years. Minimizes weeds and holds moisture well.
3 inches Pine needles Adds acid to soil. Will not mat down. Fairly durable.
6 inches Whole tree leaves Decomposes rapidly and rich in plant nutrients.
6 inches Straw Rich in potassium but decomposition takes time and may
lead to immobilization
¼ inches News paper Black ink newspapers can be used. Colour dyes may be
unsafe to soil micro-ora and fauna if composted and used
Precautions for using organic mulch
(i) Weeding must be done before spreading mulch.
(ii) Soil pH must be monitored periodically.
(iii) Restricting fungal attacks.
4. Use of plasc mulches
4.1. Applications
Tractor drawn or standalone plastic mulch layer is used to lay down plastic mulches
in large scale commercial production. The raised beds are formed, plastic is rolled
out on top, and seedlings are transplanted through it. Drip irrigation is often required

60 Protected Cultivation and Smart Agriculture
with drip tape laid under the plastic, as plastic mulch is impermeable to water. Do
not use plastic mulch without irrigation. As a result of trapping dry and moist soil
with different color plastic mulches, a signicant increase in the soil temperature was
observed. The various uses of plastic mulches are described below:
4.1.1. Bed preparation
Now a day’s several machines are available for preparation of beds like rotavator
etc. First the soil is raised in one operation and then the beds are compressed and
according to the soil condition and type. Beds spacing from center 1.5-1.8 m to run
equipment. For commercial vegetable production a bed of 12 × 90 cm with slopes
from the centre to the edge of 3 cm is commonly used. They will allow excess rainfall
to drain the mulch.
4.1.2. Placing drip lines
Drip irrigation is the most effective and suitable method of irrigation under mulched
crop. Therefore, the drip lines are laid after preparation of beds with the help of
tractor or manually as per need of the vegetable crop. Generally, for tomato, brinjal
and cucurbits, a single drip line is laid whereas two lines are laid for Cole crops and
three lines for onion and garlic crops on an 80 to 90 cm wide bed.
4.1.3. Laying mulch
The plastic mulch of our choice is covered on the beds with the help of a tractor
drawn machine or manually after placing the drip lines on beds. Farmers should give
sufcient time to adjust the plastic laying machine so that the press wheels hold the
plastic rmly against the beds and the covering discs place soil half way up the side
of the beds but not on top of it. The plastic mulch can be concealed manually in a
way that two persons can hold the plastic roll with the help of a pipe and two persons
can press the plastic by putting soil with spades. The plastic mulches are available
in rolls of 120 to 150 cm wide with length varies in the range of 0.8 to 1 km. The
thickness is usually 30-100 micron.
Mulches, by providing an insulating barrier between the soil and the air, moderate
the soil temperature. It means during the summer season, mulched soil remains
cooler over unmulched, while in the winter and spring, the mulched soils tend to
warm up more slowly than unmulched soils. Lower temperatures, moist condition
tend to slow seed germination and enhance the decay of seeds and seedlings. Plastic
can be punched exactly on drippers on the required planting distance and the crop
is transplanted accordingly. The vent should be small, only for transplanting of the
seedlings or sowing the seed in direct sown vegetable crops.
Safety measures in using plastic mulches:
1. Laying of the plastic lm shall not be done on mid-sunny days which causes
expanded condition.

Mulching: Materials, Advantages and Crop Production 61
Fig. 3: Organic and polyethylene mulching in strawberry cultivation
2. The thickness of selected black lms shall be dense as this colour is sensitive to
high temperatures.
3. Laying of lm must be loose enough to avoid the wrinkling of sheet and
expansion caused by eld operations and high day temperatures.
4.2. Types of plastic materials
The plastic materials may be either PVC or polyethylene. Polyethylene is preferred
owing to its better permeability to long wave radiation which in turn increase the
temperature around the plants during the night times.
Table 2: Type and suitability of plastic materials
Type of plastic material Best suitable for
1Based on thickness
(a) Thicker mulch Fruit crops and plantations
(b) Thin lm For early germination
(c) Thin, transparent lm Soil solarization
(d) Transparent lm Weed management through solarization
(e) Perforated mulch Weed management in cropped land
2Based on colour
(a) Black lm In monsoon season
(b) White lm Cropped eld in summer
(c) Silver colour lm Insect repellent
(d) Appropriate colour mulch Yield

62 Protected Cultivation and Smart Agriculture
5. Eect of mulching materials on soil health and crop producon
5.1. Organic mulching materials
5.1.1. Soil temperature
Crop residues on the soil surface as mulch inuences soil temperature signicantly.
Major mechanisms involved are insulation and radiant energy balance.
(a) The radiation balance is inuenced by incoming radiation by surface residue,
the evaporation of soil water and the heating of air and soil.
(b) The insulating nature of crop residues is controlled by the amount and
associated thickness of residue cover.
Straw mulching is one of the popular methods among farmers because of its easy
availability low cost and soil friendly. At the same time, utilization of rice (Oryza
sativa L.) straw mulch not only helps in conservation of soil moisture from evaporation
loss but also protect quality of vegetables from direct contact with soil surface since
pointed gourd creeper spreads on soil surface (Singandhupe et al. 2003). Under hot
arid conditions, grass mulching applied to the crop @ 6 t ha-1 insulation at 10 cm depth
by decreasing temperature from 1-7°C during monsoon season (July to September)
and 4-10°C during summer season (April to June) (Gupta and Gupta, 1983). Another
study in hot arid conditions of western Rajasthan demonstrated a drop of 1.1-5.6°C
soil temperature during summer and 0.6-3.2°C during winter (December-January) at
20 cm depth (Awasthi et al. 2006). Likewise the other straw mulches, FYM mulch
was also reported to be lower the maximum temperature by 0.4 to 4.0°C (Aggarwal
et al. 2003 and Singh et al. 2011). The lower temperature of mulched plots could
be due to the intervention of mulch to high incident solar radiation and hot air from
entering the soil layers.
5.1.2.Soil moisture content
Many researchers reported the role of crop resides as vapour barriers and soil surface
shade against moisture losses, higher inltration and surface runoff. Straw mulches
conserve more soil moisture in surface and subsurface soils leading to better root
growth and higher grain yields. Under hot arid conditions, brinjal crop with laid
mulches of local grass straws like sevan (Lasiurus sindicus) and kheep (Leptodenia
pyrotechnica) and lasoda (Cordia myxa) recorded 33-100% more moisture over
unmulched plots (Awasthi et al. 2006). Increase in inltration rate by 10-12% and
in moisture retention (-0.01 MPa) by 6-20% was observed in the inter-row spaces of
cowpea (Vigna ungiculata, Cv. FS-68) with native weeds @ 6 t ha-1 (Gupta 1986).
5.1.3. Soil aggregation/soil structure/aggregate stability
Soil organic carbon (SOC) contributed to the soil on decomposition of organic
mulches helps in the amelioration of soil structure. SOC is positively and strongly

Mulching: Materials, Advantages and Crop Production 63
correlated with aggregates stability e.g. Macro-water-stable aggregates are stabilized
by fairly undecomposed organic binding agents.
5.1.4. Soil biological properties
Moisture retention and optimum soil temperature regimes and the presence of
continuous substrate from mulching materials is conducive for decomposers. Organic
mulch is known to attenuate the rise in soil temperature and decreased diurnal
variations increase microbial activity. Furthermore, it was demonstrated that an
organic mulch increase earthworm density by 155% over bare soil.
5.1.5. Germination, seeding establishment and growth
Organic mulches produce some phytotoxic allelochemicals, which are known to
decrease the germination rate and seedling establishment. Some of the researchers
noticed the better seedling establishment in straw mulching.
5.1.6. Fertility improvement
Surface application of crop residues tends to improve soil quality viz., soil organic
carbon, structural stability, N levels by mineralization, reduction in loss of nitrates,
basic cations. In the shallow rooted crops like onion and potato, where unable to
utilize sub-soil moisture efciently, mulching helps in conserving the moisture and
allows better growth and yield.
5.2. Plastic mulching
5.2.1. Effects on plant microclimate
Plant microclimate can be altered by changing soil energy balance and by limiting
soil water evaporation. Increased root-zone temperature (RZT) is one of the major
advantages pertaining to use of plastic mulches. Under controlled conditions, root
growth increases with increase in temperature up to optimum; further increase in root-
zone temperature may adversely affect the root and shoot growth. Under controlled
conditions, optimum and maximum root-zone temperatures for plant growth are
considered and under eld conditions uctuations in air and root-zone temperatures.
5.2.2. Soil fertility
Reduction in weed menace, nutrient losses and improved hydrothermal regimes are
achieved by application of black polyethylene mulch in vegetable production. They
also buffer soil pH and exchangeable Mg and Ca more efciently. Many researchers
reported the higher yield of tomato in polyethylene mulched soil as compared to
uncovered soil owing to slow soil-water percolation and restricted nutrient loss from
the top 15 cm of soil. It was evident from experiment on nitrate leaching that nitrate
concentration three times lower in mulched soil uncovered soil.

64 Protected Cultivation and Smart Agriculture
5.2.3. Soil water conservation
Irrigation water requirement in bell pepper was decreased by 14-29% by covering
with plastic lm due to limited moisture losses. Improved water use efciency
and yield potential of tomato was achieved in polyethylene mulched soil under all
(surface and drip) levels of irrigation. In brinjal crop soil moisture of 29-56% and
22-107% conserved by using black plastic mulches over straw mulches and control,
respectively (Singh et al. 2006).
5.2.4. Plant growth and yield
It has been demonstrated that black polyethylene mulch is found to be useful in
achieving early harvest and yield of muskmelon. The yield of brinjal increased by
3.5-5.2 folds by white and black polyethylene over control probably as a result of
slow water percolation and restricted nutrient loss from the top 15 cm of soil (Singh
et al. 2006). Red and black plastic mulches were found to be effective in promoting
early yields of tomatoes due to their high temperature inducing property over white
and reective plastics. Higher early yields in tomatoes were frequently documented
for black and clear plastic mulches owing to their preferential partitioning of carbon
to fruits rather than to foliage. In contrary, high ambient temperature and high solar
radiation during the summer on using plastic mulches often results in poor growth
and low yield.
Table 3: Relationship in between plastic sheet thickness and yield of various vegetable
crops
Plastic sheet thickness (µ) Crops/ Vegetables Yield increased (%)
25 Brinjal 10-27
25 Okra 48-55
50 Potato 49-50
25 Tomato 65-70
25 Snap bean 33-73.3
25 Cucumber 44-52
50 Cabbage/Cauliower 10-71
25 Chilli 60
50 Carrot 10-50
6.5. Effect of coloured plastic mulches
Farmers must clearly dene the optimum above and below ground environments of
crop. E.g. (i) Plastic mulch increases Bermuda grass (Cynodon dactylon L.) during
the fall, but it is detrimental for weeds during summer owing to exceeding soil
temperatures harm seedlings, (ii) In a subtropical climate, peppers (Capsicum sp.)
grew faster and set fruit earlier on white plastic mulch than on straw mulches, (iii)
In a hot, semi-arid climate, black plastic resulted in scalding of the fruits and thus
reduced yields.

Mulching: Materials, Advantages and Crop Production 65
Another challenging problem with plastic mulches is removing it from the eld after
completion of the cropping season for proper disposal. Plastic mulches, especially
black plastic, do not decomposed and shall never be incorporated in the soil.
Clear plastic mulches do break down over time, but small pieces may remain in
the eld for several years. To overcome this problem several new photodegradable
or bio-degradable mulches are available serving the purpose of safe disposal after
completion of the cropping season. Selection of plastic materials must consider
plastic degradation and its effect on soil, plant and human health with its methods of
application for vegetable cultivation on commercial scale.
7. Disadvantages of mulching
Mulches do have a few drawbacks, which are as follows:
Large scale mulching is cost intensive.
Availability of mulching materials.
Use of high C:N mulching materials viz.,saw dust, straw results in temporary
immobilization or starvation for nutrients in crops.
Change in the soil reaction due to continuous use of same mulching material.
Application of top-dressed fertilizers is difcult.
Biodegradability of plastic materials
Organic mulches may harbor termites,needs frequent irrigation and spray of
termiticides.
Some of the organic mulches have allelopathic effects on crops.
8.Future scope of research
Future studies should examine a range of crop species and varieties with the objective
of identifying feasibility of different mulches whether of organic or inorganic type
capable of tolerating environmental impact, convenient in their application and
allelopathic effect on crops.
9. Conclusion
Recent progress in the understanding of mulch use in crop productions provides two
important lessons for the intensication of mulching practices especially in arid and
semi-arid areas. Firstly, selection of a particular type of mulch material whether it
is organic or non-organic, keeping in view of their (including merits and demerits)
durability, suitability/compatibility, desired above and below ground effects and
efcacy with the ambient environment as well as the crop type. In case of use of
inorganic mulches, it has been suggested that in general, black and white plastics
of 50 to 75 micron thicknesses are the most benecial synthetic mulches in winter
and summer seasons, respectively of arid and semi-arid regions. Secondly, in case

66 Protected Cultivation and Smart Agriculture
of use of organic mulches, care must be taken that it should be endowed with some
important characteristics viz., easily decomposable, capable of adding substantial
amount of organic matter to the soil, should not release allelochemicals, leguminous
in nature (especially for nitrogen decient soils), not have much economic value, C:N
ratio may ranges between 30:1 and 80:1, do not pose too much acidic, basic or toxic
effects, and available in plenty and locally. While applying the organic mulches one
should give emphasis on optimum thickness of the mulch materials not to their type.
Mulching depth of less than 2 inches is recommended for shallow-rooted vegetables
growing on poorly-drained soils (clays) and 3-4 inches for deep rooted growing on
better-drained loams or sandy soils
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