Introduction:
21st
century has witnessed a steady decline of irrigation water potential conjugated
with the ever growing global population & enhanced economic activities
among countries specially located in arid and semi arid regions of the world.
As these regions are ever facing water crisis due to uncertain and inadequate
natural precipitation, the problem with water scarcity may possibly aggravate
further. Global survey shows, the worst affected areas would be the semi arid
regions of Asia (India), the Middle-East and Sub-Saharan Africa, all of which
already face issues with heavy population growth and majority of them below the
poverty line.
It
is estimated; by 2025 water scarcity will be a major issue in India requiring
immediate redressal. As per the Central Water Commission, the demand for water
is growing at a steady rate but the availability of clean water in future is
declining even faster. In the Indian scenario, Agricultural irrigation
practices seem to be responsible for consumption of 80% of the available
potable water. There is an increasing trend to this with the further
intensification of agro based industries. Due to the large geographical
dimensions of the sub-continent and varied soil and farming practices, modern
irrigation practices can still only cater to 40% of the grown crops. The
remaining areas are far more susceptible to improper (traditional) practices
thus greatly lowering the effective and judicious use of available water for
crops.
Major drawbacks with irrigation practices
The
predominant irrigation practice is surface draining i.e. direct application of
water to crops from surface. It’s a problematic and flawed system as the crops
can utilize only 50% of the provided water while the remaining is lost in
conveyance, as runoff and by evaporation. Modern methods like drip irrigation
and use of sprinklers can effectively reduce the wastage of irrigation water but high initial costs,
inadequate government subsidy and cooperation, lack of technical input and
after sales service, faulty equipment, damage due to pests and high costs of
spares prohibits the farmers from opting these techniques.
It
is worth mentioning that 98million of the total 120million farm holdings are
small and marginal farmers; thus net income from small farms makes farmers
reluctant to adopt such water management practices in agriculture. Spatial
diversification in soil characteristics, shortage of large land holdings and
underprivileged conditions discourage farmers from adopting advantageous and
economical application of water conserving irrigation techniques, even in arid
zones with distinct scarcity of water. The stress on sustainable development
practices even in the agricultural sector has laid emphasis on further judicious,
economic and optimum utilization of land, water and plant resources with the
major goal to maximize land and water productivity without threatening the
environment and available natural resources.
Super Absorbent Polymers (SAPs)
Extensive
research all over the world, particularly Iran, China, Europe and USA has led
to the development of a particular class of Super Absorbent Polymers that can
increase water use efficiency and enhance crop yield. Soil conditioning with
SAP is an interesting and innovative facet in the field of modern agriculture
as well as rainfed agriculture. It was shown that SAP materials are hydrophilic
networks that can absorb and retain large amounts of water or aqueous
solutions. Their uptake can be as high as 100,000% and even more. SAPs are in
general, small sugar like hygroscopic crystals that can be directly added to
cultivation soils. They are predominantly used for improving irrigation
efficiency; smart delivery materials that can help combat plant pathogens even
with lower pesticide dosage, reducing the quantity of soluble NPK fertilizers
per crop cycle thus greatly contributing to water and environmental conservancy
practices.
Hydrogels
Hydrogel
agriculture technology involves gel forming polymers that are insoluble water
absorbing polymers designed exclusively for agricultural use by the late
1980’s. They were developed to improve physical properties of soil to:
Increase water holding
capacity
Increase water use
efficiency
Enhance soil
permeability and infiltration rate
Reduce irrigation
frequency
Reduce compaction
tendency
Stop soil erosion, farm
run-off & surface leaching
Increase plant
performance, particularly in structure-less soils stressed with drought
condition
Hydrogels as
they are commonly called are cross-linked three-dimensional networked water absorbent
polymers. Three main types of Hydrogels have so
far been found appropriate for agricultural use:
Starch-graft copolymers
Cross-linked
Polyacrylates
Cross-linked
Polyacrylamides & Acrylamide-acrylate copolymers
Potassium
Polyacrylate is the principle material used in SAP industry and marketed as
hydrogel for agricultural use because of its longer retention and high
efficiency in soil with nil toxicity issues. They are prepared by polymerizing
Acrylic acid with a cross linker. Cross-linked polymers can hold water 400
times their own weight and release 95% of that to growing plants. Use of
Hydrogel leads to increased water use efficiency by preventing leaching and
increasing frequency for irrigation. During summer months particularly in semi
arid regions, lack of soil moisture can cause plant stress. Moisture released
by hydrogel close to root area helps reduce stress and increase growth and
plant performance. Hydrogels can reduce fertilizer leaching and reduce
application of pesticides.
Water Absorption with Hydrogel
Hydrogel
works as water reservoirs round the root mass zones of the plant. In presence
of water, it expands to around 200-800 times the original volume. There is
ample possibility to trap irrigation and rainwater that can then be collected,
stored and gradually released for crop requirements over prolonged durations.
Hydrogel mixed with soil increase soil permeability and improve germination
rates. It is compatible with a wide range and type of soils and thus has in
general a tendency to increase plant performance and yield. Rainwater retention, soil erosion by storm
water run-offs, especially in sloped terrains can be greatly averted. There has
been proof of decrease in fruit & vegetable loss due to insect by around
10-30%.
Agriculture specific applications of Hydrogel
Hydrogel
application in agriculture in terms of proposed practices and their advantages
are summarized herein.
Conservation in Agricultural Lands
Addition
of hydrogel polymer can increase water retention capacity of soil by 50-70%
with proper amendment with various dosages of soil to hydrogel ratio. Consecutively
soil bulk density can reduce by 8-10%. There is an upward trend in saturated
water volumetric content of soil with increasing dose of hydrogel showing clear
signs of increase in agricultural water use efficiency in arid and semi-arid
regions. This has positive impact on the net plant yield. Hydrogel directly
influences soil permeability, density, structure, texture, evaporation and
infiltration rates of water. Irrigation frequency, compaction tendency and
run-offs decrease while aeration & microbial activity is promoted.
Increase in Irrigation Efficiency
Water
stress due to scarcity of moisture around root zones is often associated with
premature leaf shedding, decreasing chlorophyll content, reduced seed yield,
less fruit and flower yield per plant. Use of hydrogel can help moderate these
impacts caused by deficit irrigation. Being a water retaining agent greatly
increase irrigation period of cultivation, enhancing irrigation efficiency
particularly in arid & semi-arid belts.
Drought Stress Reduction
Drought
stress can lead to production of Oxygen radicals that result in increased lipid
perioxidation and oxidative stress in the plants. Visible effects include
stunned height, decrease in leaf area and foliar matrix damage etc. Hydrogel
can reduce drought impact on plants leading to reduced stress and oxygen radical
formation. This in turn provides scope for better growth and yield even in
unfavorable climatic conditions.
Enhanced Fertilizer Efficiency
Irrigation
technology has major constraints in the fields of application of fertilizers,
herbicides and germicides. Studies suggest the use of synthetic fertilizers can
be greatly reduced when hydrogel agriculture is practiced without hindering
with crop yield and nutritional value. It would indeed be a more appropriate
practice for sustainable agriculture in arid and semi-arid conditions and
regions with similar ecological constrains. Moreover, potassium polyacrylate is
safe and non-toxic thus prevents pollution of agro ecosystems.
Biodegradability of Hydrogel Polymer
Studies
have confirmed that hydrogel is sensitive to the action of UV rays, and
degrades into oligomers. The Polyacrylate becomes much more sensitive to
aerobic and anaerobic microbiological degradation and can degrade at rates of
10-15% per year into water, carbon dioxide and nitrogen compounds. The hydrogel
molecules are too voluminous to be absorbed into plant tissue and have zero
bioaccumulation potential.
Application rates
Considering
the efficiency of hydrogel in soil conditioning and moisture retention, it can
be understood that an optimum mixing ratio is needed to get maximum efficacy of
the method. Since the moisture holding capacity is a function of soil
characteristics, dosage of hydrogel is also varied and designed based on the
type of soil it is used with. A simple dosage chart has been illustrated herein
but the ultimate quantity and application can only be determined after testing
specific soils to be conditioned.
Type of Soil
|
Suggested dosage of
Hydrogel
|
Arid & Semi-arid Regions
|
4-6g/kg soil
|
For all level of water
stress treatment and improved irrigation period
|
2.25-3g/kg soil
|
To delay permanent wilting point in sandy soils
|
0.2-0.4g/kg OR 0.8% of
soil whichever is more
|
To reduce irrigation
water by 50% in loamy soil
|
2-4g/ plant pit
|
To improve relative water content and leaf water use efficiency
|
0.5-2.0g/pot
|
To reduce drought stress
|
0.2-0.4% of soil
|
To prohibit drought stress totally
|
225-300kg/ha of
cultivated area
|
To decrease water stress
|
3% by weight
|
ALSTA HYDROGEL: SUPER ABSORBANT POLYMER for AGRICULTURE
ALSTA
HYDROGEL is a potassium polyacrylate based super absorbent polymer manufactured
by Chemtex Speciality Ltd. for agricultural sector. The granular polymer has a
capacity to absorb water 300-500 times its own weight and release it gradually
directly to the plant roots over a period. It is effective at reducing
irrigation frequency, maintaining soil texture and permeability while ensuring
proper and healthy growth of the plants themselves. It can be used conveniently
with de-ionized and de-mineralized water to retain soil moisture as well as
reduce use of synthetic NPK fertilizers.
ALSTA
HYDROGEL is non-toxic and does not bioaccumulate. Under proper soil conditions,
it has a long working life without any adverse impact on the agro-ecosystem. It
is an easy to use farmer friendly product compatible with a large array of soil
types. It finds large scale applications in Open
Field & Protective Cultivation, Terrace Farming, Vertical Farming, Domestic
Gardens, Arboriculture, Bare Root Dripping, Hydro Seeding, Hydroponics etc.
The
salient features of ALSTA HYDROGEL include:
Reduction in fertilizer and herbicide leaching
Improvement in soil and soilless media characteristics
Enhanced seed germination and seedling growth
Increases root growth and density
Moderates drought stress significantly
Reduction in nursery establishment period
Reduction in irrigation frequency
Prevents premature defoliation
Increases fruiting/flowering density
Increases overall growth and plant biomass
ALSTA
HYDROGEL is the economical and eco-friendly step to a better water management
system for all types of agriculture systems, especially in arid and semi-arid
regions without compromising with the crop yield.
Find out more at http://www.hydrogelagriculture.com/
