Water is a very essential element in life. Several challenges can lead to water scarcity. Rainfall cannot be fully relied on as the main source of water. Due to the challenges posed by water scarcity, new innovations continue to be made as means of combating water scarcity in many regions of the world.
Super absorbent polymers are generally made of molecules that have the ability to hold and store water in very small volumes. This is possible due to the extreme concentration of molar masses in the molecules and a huge number of recurrent units in the molecules (Zhou Zhenmin, 2009).
As a result of chemical reactions, the molecules are sequentially joined into monomers. Hydro gels ensure that an area is constantly dumpy. The super absorbent polymers and the hydro gels are water absorbent materials (Zhong, Zheng, Mao,Lin, & Jiang, 2012).
Both the polymers and the hydro gels do not get absorbed by the plants. They are only used as water retention materials. In hospitals, they can be used for absorbing and solidifying water and blood (Zhang, Yuan, Wang, Gu, & Zhang, 2007).
Physicians use them together with dressing materials to absorb water from patients’ wounds when dressing the wounds (Zhang, Tanaka, &Shibayama, 1992).
In agriculture, they are used to provide water to the plants. Fire fighters use super absorbent materials to extinguish fire (Yandong Zhao, Junfu Zhang, Jinfeng Guan, &Weilun Yin. 2009).
The comparison of United Arab Emirates to other countries in terms of weather and environmental characteristics
The United Arab Emirates has the same environmental characteristics as countries such as Saudi Arabia, Qatar, Iran, Mexico and Israel but so many of the mentioned countries have not embraced the use of super absorbent polymers in agriculture and especially in the reduction of the amount of water used in irrigation.
The mentioned countries should embrace the use of super absorbent polymers as they share the same environmental characteristics with the UAE.
Such attempts would help these countries to enhance agricultural production, to conserve soil moisture and to also prevent the loss of water through methods of agriculture like irrigation. Super absorbent polymers are used in the United Arab Emirates which is located in a hot region (Nonwovens& Technical Textiles, 2009).
The UAE being a hot region has discovered ingenious ways of using the super absorbent polymers for several purposes.
The purpose of this study is to focus on the possibility of the use of super absorbent polymers in agriculture in other parts of the world too with an aim of reducing water used in irrigation (Vico&Porporato, 2011).
Focus on potassium polyacrylate, sodium polyacrylate, cellulose polymer, polyacrylamide, rechargeable solid water, solid water technologies in Australia and zeoplant will provide a thorough examination of the available super absorbent water polymers and the features associated with each of them.
Potassium polyacrylate is commonly referred to as solid rain. It was developed by engineer Sergio Rico of the National Polytechnic Institute in Mexico. He was inspired by how babies’ diapers work. He observed that diapers are capable of storing large amounts of liquid in a very small space.
Water in potassium polyacrylate is stored in molecular form. Potassium polyacrylate changes the water molecule into a hydro gel but does not change the chemical structure of the water. Potassium polyacrylate’s water retention capacity is 500 times that of its own weight.
The potassium hydro gels are meant to be placed near the roots of plants. They work with all types of trees ranging from seedlings, fodder, food crops and forests. Potassium polyacrylate solid blocks are capable of replenishing themselves (Wilson, 2012).
With potassium polyacrylate, only minimum evaporation takes place eventually saving on the amount of water required.
Potassium polyacrylate works very well with water soluble fertilizers meaning that when combined with soluble fertilizers, it can nourish the plants by ensuring slow release of nutrients from the fertilizers to the crops.
This constant supply of nutrients to the plants ensures that plants are healthy and that the productivity of plants is increased by 100%.Potassium polyacrylate can be placed in the plant’s hole just before transplanting can take place.
This ensures that the crop is hydrated throughout by the moisture released by the potassium polyacrylate solid or capsule. With the use of potassium polyacrylate products, farmers are able to save on irrigation costs and reduce the costs by 75%.
A survey carried out in the UAE showed that the application of potassium polyacrylate in plants ensures that the plants stay up to 5 months without been watered (www.aquawarehouse.net/data_en.pdf). Water salinity affects water retention and water absorption capabilities.
The presence of lime, iron and phosphate in the water is known to greatly affect the water holding and retention capacities of potassium polyacrylate (Vico&Porporato, 2011). Potassium polyacrylate has several advantages.
To create and use a potassium polyacrylate polymer, one only needs to follow very simple instructions of just mixing the right amount of water with the right amount of potassium polyacrylate. Potassium polyacrylate takes only 15 minutes to solidify and form the polymer. (farooqis2cool.hubpages.com/…/The-Man-Who-Invented-Solid-Rain -).
With the formation of potassium polyacrylate solid blocks, it is quite easy to transport them. Potassium polyacrylate is good in absorbing chemical spills. This is ideal especially in industries where dangerous and hazardous chemicals or chemical spills may be emitted on roads during transportation.
Cleaning of such chemical spills can be tricky. Potassium polyacrylate is very much applicable in horticultural farming since it requires constant irrigation where it can be used as a substitute for irrigation (The WaterCAMPWS ,2012).
To irrigate large sectors of land, high capital costs are required. Research indicates that traditional irrigation methods incur a lot of costs in terms of labor, energy and time especially if overhead irrigation is employed. A lot of work is involved in the construction of network water pipes.
A lot of money is also required in the purchasing of the irrigation materials which are the pipes, the sprinklers and so on. Once the potassium polyacrylate is put into the ground, it usually takes several months before it replenishes itself.
Potassium polyacrylate is used effectively in regions that experience long draughts like the United Arab Emirates and some parts of South and North Africa. In these regions, potassium polyacrylate polymer solid blocks can be used in reforestation since they are capable of providing moisture to the trees for a long period of time.
In these regions, the forest cover is usually very low (Tejero, Zuazo, Bocanegra&Fernández, 2011). To increase the forest cover, new forests may be created and the water retention capacity can be enhanced with the use of potassium polyacrylate right from the stages of growth of the seeds in the tree nurseries to that of transplanting them to the areas where they will be planted.
Potassium polyacrylate can be used to ensure that the trees are properly hydrated (Spangler, 2012). Food security poses a big challenge to arid and semi arid areas. Potassium polyacrylate polymers can be used to fight the challenges of food crises.
Since potassium polyacrylate comes in form of small capsules that are easy to transport and are very affordable, farmers can use them for plants and food crops. Farmers will be guaranteed of full productivity of all their food crops through the use of polyacrylate polymers.
Surveys and pilot projects carried out in the dry regions of the world indicate a 100% rise in the productivity of the crops if potassium polyacrylate is used (Ruiqiang Zhang, &TianmingGao. (2011). Most of the hot regions have sand and cotton soils whose water retention capacities are very low.
Potassium polyacrylate polymer solid blocks can be used to enhance the water retention capabilities for sand soils (Liu Xiaochu, Ling Jingpeng, Yao Li, Wu Hualong, & Tao Jianhua, 2010). Cotton soils are known for poor drainage capabilities.
Potassium polyacrylate polymers are able to fix these types of challenges since they provide continuous moisture throughout the period of their uses. Arid and semi arid areas are frequented by dangerous forest fires especially during the hot season.
These fires spread so fast especially if there are presence of strong winds. Use of potassium polyacrylate is an ideal way of extinguishing forest fires. The water retained in potassium polyacrylate is exactly what stops the fires in these types of situations.
United Arab Emirates being a semi arid region has experienced the challenge of maintaining green lawns and landscapes. This can be very well fixed by the use of potassium polyacrylate other than depending on rainfall for water.
It is widely used in most consumer products. Sodium polyacrylate uses the principle of osmosis (Rechargeable solid water, 2009). Osmosis refers to the movement of water molecules from regions of high concentration to regions of low concentration.
Sodium polyacrylate can attract water molecules from liquid water to itself since its water concentration is low.
With distilled water, sodium polyacrylate is capable of absorbing distilled water up to 800times its weight and 300times that of non- distilled water (depts.washington.edu/chemcrs/bulkdisk/…/notes_Sodium-Polyacrylate.pdf).
Hard water essentially consists of calcium, zinc and iron. Sodium polyacrylate is used as a sequestering agent in most detergents (Qu, G., & de Varennes, A.2010).This helps the detergent to dissolve into the chemicals found in hard water (Orzolek, 1993).
The detergent then becomes effective in the removal of dirt and also in the clearing of foul smells. Sodium polyacrylate is used as a coating agent. It is used to coat some electrical wires that are likely to pass through dump areas.
The sodium polyacrylate coating helps to ensure that the electrical wires do not come into contact with any moisture. With fire accidents posing a big challenge at homes and in industries, there is a great need for fireproof walls, doors, furniture and equipments.
Sodium polyacrylate is used to coat all these components by providing them with its fire proof capabilities (Nonwovens & Technical Textiles, 2009). Sodium polyacrylate is used by florists to retain moisture in freshly cut flowers making them to last longer.
Nasal astronauts are required to keep some form of moisture during their space expeditions. They use special spacesuits which are treated with sodium polyacrylate. This helps them to prevent rashes (National, 2012).
Sodium polyacrylate is also used as a thickening agent. This helps the component to hold and absorb so much water. This is the concept used in babies’ diapers and hair gels. Through osmosis, water molecules are drawn from the urine. The climatic conditions in the United Arab Emirates are generally hot.
Sodium polyacrylate may be used in horticulture more so in the flower industries. Sodium polyacrylate may be used to preserve the flowers’ freshness after harvesting and during delivery for export markets since the hot weather can drastically reduce the quality of the flowers. Sodium polyacrylate is known to be non toxic.
However, it causes irritation of the eyes and the nose. Care should therefore be exercised when handling it for example through the use of gloves and face masks to prevent it from coming in to contact with the face.
Cellulose polymers are made of organic compounds and comprise 33% of plant matter (Liu,Ling,Yao,and Wu & Tao,2010).With the use of a glucose monomer, a molecule can dissolve in other chemicals to form a polymer that is the organic compounds in cellulose form a cellulose polymer (Li, & Wang, 2005).
Through glucocisidic bonds, starch monomers bind to form cellulose polymers (Bruce et al, 2008). Most of the cellulose polymers come from plant matter (Leiva, & Skees, 2008). The molecular weight of a monomer is measured in units called dimmers (Krul, Nareiko, Matusevich,Yakimtsova, Matusevich, &Seeber, 2000).
Cotton is known to have the highest percentage of cellulose at 90% followed by wood at 50%.Cellulose is usually odorless. It is also tasteless. A super absorbent polymer from cellulose is formed by a cross link of carboxymethly cellulose and vegetable starch from either a cassava or a potato.
A survey was carried out to test the efficiency of this type of cellulose polymer (academic journals.org.ssem/pdf/pdf2012/july/nnadi%and%20 Brave.pdf). Two plant nurseries were used.
One plant nursery was treated with cellulose polymers and the other one was not. Radish seeds were eventually planted into the two nurseries. The two nurseries were continuously given water for two weeks and then water was stopped for the next three weeks.
Two weeks later, the plants from the nursery that was not treated with cellulose polymers showed serious signs of dehydration effects. On the nursery that had been treated with cellulose polymers, 73% of water retention was noted. Cellulose polymers offer good germination energy to plants.
Cellulose polymers are made of degradable materials. This makes them environmental friendly. They are characterized by very short life spans of up to 6 months.
Though they are highly absorbent, their absorption capabilities are not as high compared to potassium based and sodium based polymers. They can only retain water up to 20 times their own weight.
This is a type of polymer that is capable of absorbing water up to 400times its own weight. It has a longer life span compared to potassium polyacrylate and sodium polyacrylate. It is also cheaper compared to potassium polyacrylate and sodium polyacrylate (www.indiantextilejournal.com/articles/FAdetails.asp?id=1932).
When hydrated, polyacrylamide forms crystals that look like water (Nonwovens, 2009). Light can pass through the crystals though it cannot be refracted.
When polyacrylamide crystals are put in a glass, they are invisible but when they are removed from the glass they become visible (Guiwei, deVarennes, Martins, Mourato, Cardoso, Mota, Gonçalves, 2010). That is the reason why sometimes they are called ghost crystals.
Polyacrylamide polymers are made in various forms of either dry granules or solid blocks. Polyacrylamide polymers are ideal for use in agriculture to provide water to the plants.
Since polyacrylamide polymers’ granules or solids are placed in the plant rooting system, there is no water flow or movement that takes place forcing the soil to erode. Polyacrylamide polymers are then said to reduce soil erosion up to 95%. With polyacrylamide polymers, it is possible to undertake hydraulic mulching.
Water and seeds are put in a state and environment that speeds up germination. In coal processing, water is essentially required. After the coal processing, water should be eliminated from the coal and this can reduce transportation costs of the coal.
Polyacrylamide polymers are very ideal for use in coal processing to absorb the water in the coal after the processing. Coal is mainly processed in the Middle East, United Arab Emirates, some parts of South Africa and some other parts of North Africa. Polyacrylamide polymers can be used in all these regions.
These regions are semi arid characterized by light textured types of soils. With traditional irrigation methods, soil erosion can be very excessive leading to mass erosion of the top cover soils in the long run. These regions are frequently faced with food shortages that makes then turn to importing food for their populations.
With the use hydraulic mulching, speeding up of seeds germination will shorten the time taken in food production processes.
Rechargeable solid water in the UAE
This type of polymer is insoluble in water. A gel like suspension is created when the polymer is put in water. Water recharging can take place in 30 days intervals.
Rechargeable solid water is ideal for plant nurseries, forests, horticulture, landscaping and commercial and domestic farming. Rechargeable solid water is ideal for arid and semi arid areas (www.outsidetheboxdistributors.com/solidwater.html) (www.gumtree.com.au/s-plants+large/page-5/k0).
Liquid fertilizers can be mixed with rechargeable solid water to provide continuous release of plant nutrients. Rechargeable solid water is non toxic. It is also biodegradable. It has a 2 years lifespan. In the United Arab Emirates, landscapes need to be kept green especially in airports, school grounds and other public grounds.
To ensure lawns, flower beds and potted plants remain green throughout; rechargeable solid water can be used. With traditional irrigation, huge sums of money may be used constantly to irrigate these landscapes. More time will be required for continuous irrigation. A lot of water will also be saved.
Solid water technologies in Australia
The solid water technologies are efficient in providing water to the plants for they offer a steady supply of water to the roots of the plant (Gao, Wang, Li, Fu, Wu, Wang, & Wang, 2008). They are environmentally friendly for they comprise of organic matter.
This technology is ideal for tree nurseries, flower pots, flower gardens and kitchen gardens. This is because its frequency of drainage can last for a maximum of 3 months and has a one year life span (www.strategicforesight.com/Arab%20Water%20World.pdf).
Zeoplant is normally used to amend soils. When added to the soil, it treats it with natural minerals and organic components (Farooq, 2012). Its water retention capacity is increased. This can reduce irrigation costs by 85%.
Zeoplant can retain water up to 420 times its own weight. Zeoplant can be used basically in all types of soils. Zeoplant is very ideal for areas like the semi arid areas in the Middle East and UAE.
The innovation of super absorbent polymers is a great milestone towards overcoming the challenge of water shortage in the UAE and other dry regions in the world. Stakeholders should join together to make sure problems brought about by water shortage crises are dealt with effectively.
Potassium polyacrylate commonly called solid rain best suits the climatic conditions of the United Arab Emirates. The climatic conditions in the United Arab Emirates are generally dry creating water scarcity especially for agriculture.
With its high absorbent features and ability to work with all types of crops, potassium polyacrylate is the best polymer for the United Arab Emirates. It can therefore replace water irrigation in this country.
Zeoplant is also ideal for use in the United Arab Emirates due to its ability to amend soils and ensure that the soils retain the required moisture and nutrients for crop development.
Sodium polyacrylate may have some limitations since care must be exercised when handling it due to its irritability to the skin, eyes and nasal membranes. Polyacrylamide may also not be ideal because it has been linked to toxicity in plants.
To some extent, the polymer is absorbed in water molecules creating the likelihood for it to be transferred to other plants. There are not many major research projects that have been undertaken in this field (Fang, Ma, Yu, Ahuja, Malone, &Hoogenboom, 2010).
Governments in developing countries should aggressively train chemical engineers to avoid over reliance on engineers from the developed countries (Esteves, 2011).
Governments should offer full scholarships to their students to go and study about polymers in developed countries (Blanke, Rozelle, Lohmar, Wang, & Huang, 2007). The costs of most super absorbent polymers are relatively high and may not be affordable to peasant farmers (Bidisha, Joerg, &Yakov, 2010).
Governments involved should look in to giving tax subsidies towards super absorbent polymers. In areas of extreme poverty, the governments concerned should look in to providing super absorbent polymers for free to farmers (Berber, Hafez, Minagawa, Tanaka, & Mori).
Though there are clear instructions on how to use the super absorbent polymers, training of farmers on the uses of super absorbent polymers should be encouraged.
This would also eliminate the misconceptions that are likely to arise due to failure by the farmers to understand the role played by super absorbent polymers (Asghar,Samad, & Hashaikeh, 2012).
Training farmers can be done by use of creating demonstration farms where individual farmers or groups can visit the farms for learning purposes (AquaWarehouse, 2009). Countries that employ the use of water absorbent polymers especially in agriculture must also come up with clear guidelines on their usage.
The use of guidelines would spell out standards required for use of water absorbent polymers that any country would wish to implement (AquaWarehouse, 2009).
The standards set would apply to all manufacturers, importers and suppliers of the water absorbent polymers. It is also good for them to create a body with a mandate to check on the standards of the water absorbent polymers (Andry, Yamamoto, Irie, Moritani, Inoue& Fujiyama, 2009).
Proper use of water absorbent polymers can play a major role towards the improved economy of any country (Achtenhagen&Kreuzig, 2011).
Research has proved that with the use of water absorbent polymers, irrigation costs drastically go down, plant mortality is greatly reduced and there are minimal risks of hydro gels getting absorbed by the plants (Abdulai, Owusu&Bakang, 2011).
Public awareness campaigns especially through the media should be carried out so as to make most people aware of the availability of water absorbent polymers. The use of other conventional methods of water conservation should not be ignored (Abd El-RehimHegazy&Abd El-Mohdy, 2004).
Abd El-Rehim, H. A., Hegazy, E. -. A., &Abd El-Mohdy, H. L. (2004).Radiation synthesis of hydrogels to enhance sandy soils water retention and increase plant performance. Journal of Applied Polymer Science, 93(3), 1360-1371.
Abdulai, A., Owusu, V., &Bakang, J. E. A. (2011). Adoption of safer irrigation technologies and cropping patterns: Evidence from southern ghana. Ecological Economics, 70(7), 1415-1423.
Achtenhagen, J., &Kreuzig, R. (2011). Laboratory tests on the impact of superabsorbent polymers on transformation and sorption of xenobiotics in soil taking 14C-imazalil as an example. Science of the Total Environment, 409(24), 5454-5458. doi: 10.1016/j.scitotenv.2011.09.021
Andry, H., Yamamoto, T., Irie, T., Moritani, S., Inoue, M., & Fujiyama, H. (2009).Water retention, hydraulic conductivity of hydrophilic polymers in sandy soil as affected by temperature and water quality. Journal of Hydrology, 373(1–2), 177-183. doi: 10.1016/j.jhydrol.2009.04.020
AquaWarehouse. (2009). Keeps and saves water for when you need it. Retrieved from http://www.aquawarehouse.net/data_en.pdf
Asghar, A., Samad, Y. A., & Hashaikeh, R. (2012). Cellulose/PEO blends with enhanced water absorption and retention functionality.Journal of Applied Polymer Science, 125(3), 2121-2127.
Asociados, D. (2012). LIuviasolida. Retrieved from http://www.lluviasolida.mx/descargas/English_version.pdf
Berber, M. R., Hafez, I. H., Minagawa, K., Tanaka, M., & Mori, T.An efficient strategy of managing irrigation water based on formulating highly absorbent polymer-inorganic clay composites. Journal of Hydrology, (0) doi: 10.1016/j.jhydrol.2012.08.051
Bidisha, M., Joerg, R., &Yakov, K. (2010).Effects of aggregation processes on distribution of aggregate size fractions and organic C content of a long-term fertilized soil. European Journal of Soil Biology, 46(6), 365-370. doi: 10.1016/j.ejsobi.2010.08.001
Blanke, A., Rozelle, S., Lohmar, B., Wang, J., & Huang, J. (2007).Water saving technology and saving water in china. Agricultural Water Management, 87(2), 139-150. doi: 10.1016/j.agwat.2006.06.025
Esteves, L. P. (2011). Superabsorbent polymers: On their interaction with water and pore fluid. Cement and Concrete Composites, 33(7), 717-724. doi: 10.1016/j.cemconcomp.2011.04.006
Fang, Q., Ma, L., Yu, Q., Ahuja, L. R., Malone, R. W., &Hoogenboom, G. (2010). Irrigation strategies to improve the water use efficiency of wheat–maize double cropping systems in north china plain. Agricultural Water Management, 97(8), 1165-1174. doi: 10.1016/j.agwat.2009.02.012
Farooq. (2012). The man who invented solid rain. Retrieved from http://farooqis2cool.hubpages.com/hub/The-Man-Who-Invented-Solid-Rain
Gao, J., Wang, A., Li, Y., Fu, Y., Wu, J., Wang, Y., & Wang, Y. (2008). Synthesis and characterization of superabsorbent composite by using glow discharge electrolysis plasma. Reactive and Functional Polymers, 68(9), 1377-1383. doi: 10.1016/j.reactfunctpolym.2008.06.018
Guiwei, Q., de Varennes, A., Martins, L. L., Mourato, M. P., Cardoso, A. I., Mota, A. M.,… Gonçalves, M. L. (2010). Improvement in soil and sorghum health following the application of polyacrylate polymers to a cd-contaminated soil. Journal of Hazardous Materials, 173(1–3), 570-575. doi: 10.1016/j.jhazmat.2009.08.124
Krul, L. P., Nareiko, E. I., Matusevich, Y. I., Yakimtsova, L. B., Matusevich, V., &Seeber, W. (2000). Water super absorbents based on copolymers of acrylamide with sodium acrylate. Polymer Bulletin, 45(2), 159-165.
Leiva, A. J., &Skees, J. R. (2008). Using irrigation insurance to improve water usage of the rio mayo irrigation system in northwestern mexico. World Development, 36(12), 2663-2678. doi: 10.1016/j.worlddev.2007.12.004
Li, A., & Wang, A. (2005).Synthesis and properties of clay-based superabsorbent composite. European Polymer Journal, 41(7), 1630-1637.
Liu Xiaochu, Ling Jingpeng, Yao Li, Wu Hualong, & Tao Jianhua. (2010). Engineering quality control of solar-powered intelligent water-saving irrigation. Informatics in Control, Automation and Robotics (CAR), 2010 2nd International Asia Conference on, 3 254-257.
National. (2012). Scientist creates solid rain to help states with drought. Retrieved from http://www.expresiontotal.com/en/general/cientifico-crea-lluvia-solida-para-ayudar-a-los-estados-con-sequia
Nonwovens & Technical Textiles. (2009). Super absorbent polymers: Highlights on PAC & PAM. Retrieved from http://www.indiantextilejournal.com/articles/FAdetails.asp?id=1932
Orzolek, M. D. (1993). Use of hydeophylic polymers in horticulture. Retrieved from http://horttech.ashspublications.org/content/3/1/41.full.pdf
Qu, G., & de Varennes, A. (2010).Use of hydrophilic polymers from diapers to aid the establishment of spergulariapurpurea in a mine soil. Journal of Hazardous Materials, 178(1–3), 956-962. doi: 10.1016/j.jhazmat.2010.02.031
Rechargeable solid water. (2009). Retrieved from http://www.rechargeablesolidwater.ca/index.htm
Ruiqiang Zhang, &TianmingGao. (2011). The research on how different irrigation amount affects the vegetation of degraded grassland. Water Resource and Environmental Protection (ISWREP), 2011 International Symposium on, 3 1658-1659.
Spangler, S. (2012).Water absorbing crystals. Retrieved from http://www.stevespanglerscience.com/experiment/water-absorbing-crystals
“Solid rain” captures water in a solid for irrigation. (2012). Retrieved from http://cleantechconcepts.com/?p=154
Tejero, I. G., Zuazo, V. H. D., Bocanegra, J. A. J., &Fernández, J. L. M. (2011). Improved water-use efficiency by deficit-irrigation programmes: Implications for saving water in citrus orchards.ScientiaHorticulturae, 128(3), 274-282. doi: 10.1016/j.scienta.2011.01.035
The WaterCAMPWS.(2012). Super absorbent polymers. Retrieved from http://www.watercampws.uiuc.edu/waterclear/labs/lessons/polymers_teacher_guide.pdf
Vico, G., &Porporato, A. (2011). From rainfed agriculture to stress-avoidance irrigation: II. sustainability, crop yield, and profitability. Advances in Water Resources, 34(2), 272-281. doi: 10.1016/j.advwatres.2010.11.011
Wilson, S. (2012). SOLIDWATER. Retrieved from http://solidwater.com.au/index.html
Yandong Zhao, Junfu Zhang, Jinfeng Guan, &Weilun Yin. (2009). Study on precision water-saving irrigation automatic control system by plant physiology. Industrial Electronics and Applications, 2009.ICIEA 2009. 4th IEEE Conference on, 1296-1300.
Zhang, J., Yuan, K., Wang, Y., Gu, S., & Zhang, S. (2007). Preparation and properties of polyacrylate/bentonite superabsorbent hybrid via intercalated polymerization. Materials Letters, 61(2), 316-320. doi: 10.1016/j.matlet.2006.04.055
Zhang, Y. -., Tanaka, T., &Shibayama, M. (1992). Super-absorbency and phase transition of gels in physiological salt solutions. Nature, 360(6400), 142-144.
Zhong, K., Zheng, X., Mao, X., Lin, Z., & Jiang, G. (2012).Sugarcane bagasse derivative-based superabsorbent containing phosphate rock with water–fertilizer integration. Carbohydrate Polymers, 90(2), 820-826. doi: 10.1016/j.carbpol.2012.06.006
Zhou Zhenmin. (2009). Influence of irrigation water-saving on groundwater table in the downstream irrigation districts of yellow river.Natural Computation, 2009.ICNC ’09. Fifth International Conference on, 3 421-424.