The application of superabsorbent polymers (SAPs) and/or biochars to stressed lands offer solutions to several critical ecological, energy and economic challenges posed by degraded lands due to human activities. These substances are like, ‘artificial humus’ as they are hydrophilic and contain carboxylic groups (SAPs) which enable them to bind cations and water, and sequester carbon from air to reverse global warming (biochars). Several research studies using these substances point to their ability to increase the plant-available water in the soil which enables the plants to survive longer with water shortage, increase soil fertility and agricultural yields, improve soil structure, aeration and water penetration, reduce use of synthetic fertilisers and pesticides, reduce nitrous oxide and methane emission from soil, reduce nitrate and farm chemicals leaching into watersheds, convert green and brown wastes into valuable resources, and reduce the evapotranspiration rate of the plants. SAPs and biochars induce a significantly higher growth rate in plants; they bind heavy metals and mitigate their action on plants as well as mitigate the effects of salinity. This paper reviews what is known about these claims and considers the wider environmental implications of the adoption of these processess. The intention is not just to summarise the current knowledge but also to identify gaps that require further research.
An introduction to the United Nations Convention to combat desertification, UNCCD, Bonn2008.
2.
LalR. (2007) Anthropogenic influences on world soils and implications to global food security. In: SparksD.L. (ed.), Advances in agronomy, Vol. 93. Academic Press, San Diego.
3.
SivakumarM. V. K., and StefanskiR. (2007). In: SivakumarM.V.K., and NdianguiN. (eds), Climate and land degradation, p. 105. Springer, Berlin.
4.
BotA. J., NachtergaeleF. O., and YoungA. (2000) Land resource potential and constraints at regional and country level. World Soil Resources Report 90, Land and Water Development Division, Food and Agriculture Organization of the United Nations, Rome.
5.
LalR. (2001) Soil degradation by erosion. Land Degrad. Dev., 12, 519.
6.
ConacherA. (1998). In: ConacherA.J, and SalaM. (eds), Land degradation in Mediterranean environments of the world. nature and extent, causes and solutions, p. 175. John Wiley and Sons, Chichester.
7.
MillsA. J., and FeyM. V. (2004) Effects of vegetation cover on the tendency of soil to crust in South Africa. Soil Use Manage., 20, 308.
8.
SuY. Z., LiY. L., and ZhaoH.L. (2006) Soil properties and their spatial pattern in a degraded sandy grassland under post-grazing restoration, Inner Mongolia, Northern China, Biogeochemistry, 79, 297.
9.
VeldkampE. (1994) Organic carbon turnover in three tropical soils under pasture after deforestation. Soil Sci. Soc. Am. J., 58, 175.
10.
StockingM. A. (2003) Tropical soils and food security: the next 50 years. Science, 302, 1356.
11.
MaQ. (2004) Appraisal of tree planting options to control desertification: experiences from three north-shelterbelt program. Int. Forest. Rev., 6, 327.
12.
MekuriaW. (2007) Effectiveness of exclosures to restore degraded soils as a result of overgrazing in Tigray, Ethiopia. J. Arid Environ., 69, 270.
13.
DechertG., VeldkampE., and AnasI. (2004) Is soil degradation unrelated to deforestation? Examining soil parameters of land use systems in Upland Central Sulawesi, Indonesia. Plant Soil, 265, 197. Global Planet. Change, 64, 169.
14.
LehmannJ., KernD. C., GlaserB, and WoodsW.I. (2003) Amazonian dark earths:origin, properties, management.Kluwer Academic Publishers, The Netherlands.
15.
GauntJ., and LehmannJ. (2008) Energy balance and emissions associated with biochar sequestration and pyrolysis bioenergy production. Environ. Sci. Technol., 42, 4152–4158.
ChengC.H, LehmannJ., ThiesJ.E., and BurtonS.D. (2008) Stability of black carbon in soils across a climatic gradient. J. Geophys. Res., 113, G02027
18.
LehmannJ., da SilvaJ.P.Jr., SteinerC., NehlsT., ZechW., and GlaserB. (2003) Nutrient availability and leaching in an archaeological anthrosol and a ferralsol of the Central Amazon basin: fertiliser, manure and charcoal amendments. Plant Soil, 249, 343–357.
19.
ChanK.Y., Van ZwietenL., MeszarosI., DownieA., and JosephS. (2007) Agronomic values of greenwaste biochar as a soil amendment. Austr. J. Soil Res., 45, 629–634A.
20.
LehmannJ., GauntJ., and RondonM. (2006) Bio-char sequestration in terrestrial ecosystems–a review. Mitigation and adaptation strategies for global change, Vol. 11, pp. 403–427.
21.
EkebafeM.O. (2011) Effect of palm fronds and cow dung biochars on the properties of soil supporting the oil palm. J. Chem. Soc., 36(1), 122–129.
22.
BicudoJ.R., and GoyalS.M. (2003) Pathogens and manure management systems: A review. Environ Technol., 24, 115–130.
23.
IppolitoJ. (2011) Western Nutrient Management Conf., Vol 9, Reno NV.
24.
RhodesC.J. (2012) Sci. Prog., 95, 206–208.
25.
GauntJ., and LehmannJ. (2008) Energy balance and emissions associated with biochar sequestration and pyrolysis bioenergy production. Environ. Sci. Technol., 42, 4152–4158.
EkebafeL. O., OgbeifunD. E., and OkieimenF. E. (2011) Effect of native cassava starch-poly (sodium acrylate-co-acrylamide) hydrogel on the growth performance of maize (Zea may) seedlings. Am. J., Polym. Sci., 1(1), 1–6.
28.
EkebafeL.O, OgbeifunD. E., and OkieimenF. E. (2012): Effect of cassava starch hydrogel on the water requirement of maize (Zea may) seedlings and selected properties of sandy loam soil. Int. J. Basic Appl. Sci., 1(2), 132–139.
29.
BaydinaN. L. (1996), Inactivation of heavy metals by humus and zeolites in industrially contaminated soils. Eurasian Soil Sci., 28, 96.
30.
HttermannA., ArduiniI., and GodboldD. L. (2004) In: PrasadM.N.V. (ed.), Heavy metal stress in plants, from biomolecules to ecosystems, 2nd edn, p. 295. Springer-Verlag, Berlin.
31.
HermsU., and BrmmerG (1984), Einflußgr_ßen der Schwermetalll_slichkeit und -bindung an B_den, Z. Pflanz. Bodenkunde, 147, 400.
32.
HttermannA., and ZomorodiM. (1998) German Patent 19813425 A 1.
33.
EkebafeL.O., OgbeifunD.E., and OkieimenF.E. (2012) Removal of heavy metals from aqueous media using native cassava starch-poly (sodium acrylate-co-acrylamide) hydrogel. Macromolecules, 8(2), 42–47.
34.
EkebafeL. O., OgbeifunD. E., and OkieimenF. E. (2012) Removal of heavy metals from aqueous media using native cassava starch hydrogel. Afr. J. Environ. Sci. Technol., 6(7), 275–282.
35.
TorresA. M. O., and De VarennesA. (1998) Remediation of a sandy soil artificially contaminated with copper using a polyacrylate polymer. Soil Use Manage., 14, 106.
36.
DeVarennesA., and TorresM. O. (1999) Remediation of a long-term copper contaminated soil using a polyacrylate polymer. Soil Use Manage, 15, 230.
37.
DeVarennesA., and QuedaC (2005) Application of an Insoluble polyacrylate polymer to copper-contaminated soil enhances plant growth and soil quality. Soil Use Manage., 21, 410.
38.
GrcmanH., and LestanD. (2003) Use of hydrogels in EDTA induced Pb phytoextraction. Fresenius Environ. Bull., 12, 1044.
39.
KosB. Lestan, (2003) Influence of a biodegradable (S,S.-EDDS) and nNon-degradable (EDTA) chelate and hydrogel modified soil water sorption capacity on Pb phytoextraction and leaching. Plant Soil, 253, 403.
40.
Al-OmranA. M. (1991) Impact of gel conditioners and water salinity on intermittent evaporation. Egypt. J. Soil Sci., 31, 575.
41.
HussainG., Al-GosaibiA. M., and BadawiM. H. (1992) Effect of single salt solution on water absorption by gel-forming soil conditioners. Arid Soil Res. Rehabil., 6, 83.
42.
ChatzoudisG. K., and RigasF. (1999) Soil salts reduce hydration of polymeric gels and affect moisture characteristics of soil. Commun. Soil Sci. Plant Anal., 30, 2465.
43.
HütherA., XuX., and MaurerG. (2006) Swelling of N-isopropyl acrylamide hydrogels in aqueous solutions of sodium chloride. Fluid Phase Equilib., 240, 186.
44.
SalemN (1991) Quality of irrigation waters and water uptake of a polyacrylamide hydrogel. Agrochimica, 35, 149.
45.
SalemN (1991) The use of a polyacrylamide hydrogel to improve the water-holding capacity of a sandy soil under different saline conditions. Agric. Mediterranean, 121, 160.
46.
SalemN, PiniR., VignaG., and GuidiG.V. (1995) Evaporation loss from sandy soils mixed with a polyacrylamide hydrogel under different saline conditions. Agrochimica, 39, 334.
47.
ChenS.L. (2004), Hydrogel modified uptake of salt ions and calcium in populus euphratica under saline conditions. Trees Struct. Funct., 18, 175.
48.
BowmanD. C., EvansR. Y., and PaulJ. L. (1990) Fertiliser salts reduce hydration of polyacrylamide gels and affect physical properties of gelamended container media. J. Am. Soc. HortScience, 115, 382.
49.
BowmanD. C., and EvansR. Y (1991) Calcium inhibition of polyacrylamide gel hydration is partially reversible by potassium. HortScience, 26, 1063.
50.
HendersonJ. C., and HensleyD. L. (1985) Ammonium and nitrate retention by a hydrophilic gel. HortScience, 20, 667.
51.
BresW., and WestonL. A. (1993) Influence of gel additives on nitrate, ammonia, and water retention and tomato growth in a soil-less medium. HortScience, 28, 1005.
52.
ChatzoudisG. K., and ValkanasG. N. (1995) Lettuce plant growth with the use of soil conditioner and slow release fertilizer. Commun. Soil Sci. Plant Anal., 26, 2569.
53.
AwadT., and DoeringH.D. (1994) Mobilisation of nutrients from slow-release fertiliser as influenced by hydrogel and water quality. Agrochimica, 39, 123.
54.
ZhanF. (2004) Preparation of superabsorbent polymer with slow release phosphate fertilizer. J. Appl. Polym. Sci., 92, 3417.
55.
LiuM. (2006) Synthesis of a slow-release and superabsorbent nitrogen fertiliser and its properties. Polym. Adv. Technol., 17, 430.
56.
RudzinskiW. E. (2003) pH-sensitive acrylic-based copolymeric hydrogels for the controlled release of a pesticide and a micronutrient. J. Appl. Polym. Sci., 87, 394.
57.
LiuM. (2006) Synthesis of a slow-release and superabsorbent nitrogen fertiliser and its properties. Polym. Adv. Technol., 17, 430.
58.
LanW., and LiuM (2007) Slow-release potassium silicate fertiliser with the function of superabsorbent and water retention. Ind. Eng. Chem. Res., 46, 6494.
59.
Abedi-KoupaiJ., SohrabF., and SwarbrickG. (2008) Evaluation of hydrogel application on soil water retention characteristics. J. Plant Nutr., 31, 317.
60.
LentzR. D., and KinkaidD.C. (2008) Polyacrylamide treatments for reducing seepage in soil-lined reservoirs: a field evaluation. Trans. ASABE, 51, 535.
61.
LentzR. D. (2007) Inhibiting water infiltration into soils with cross-linked polyacrylamide: Seepage reduction for irrigated agriculture. Soil Sci. Soc. Am. J., 71, 1352.
StahlJ.D., CameronM.D., HaselbachJ., and AustS.D. (2000) Biodegradation of superabsorbent polymers in soil. Environ. Sci. Pollut. Res., 7, 83–88.
66.
WallaceA., WallaceG.A., and AbuzamzamA.M. (1986) Effects of a polymer as soil conditioner on yields and mineral nutrition of plants. Soil Sci., 143, 377–380.
67.
McGrathJ. J. (1993) Teratology study of a cross-linked polyacrylate superabsorbent polymer. J. Am. Coll. Toxicol., 12, 127.
68.
HaselbachJ., HeyS., and BernerT (2000) Short-term oral toxicity study of FAVOR PAC in rats. Regul. Toxicol. Pharmacol., 32, 310.
69.
HaselbachJ. (2000) Single-dose oral toxicity study of a cross-linked sodium polyacrylate/polyvinyl alcohol copolymer in chickens (Gallus domesticus). Regul. Toxicol. Pharmacol., 32, 332.
70.
HamiltonJ. D., ReinertK. H., and McLaughlinJ. E. (1995) Aquatic risk assessment of acrylates and methacrylates in household consumer products reaching municipal waste-water treatment plants. Environ. Technol., 16, 715.
71.
FiumeM.Z. (2002) Final report on the safety assessment of acrylates copolymer and 33 related cosmetic ingredients. Int. J. Toxicol., 21, Suppl. 3, 1.
72.
Garay-JimenezJ. C. (2008) Methods for purifying and detoxifying sodium dodecyl sulfate-stabilised polyacrylate nanoparticles. Nanomedicine, 4, 98.
73.
Diaz-RavinaM. R. (2006) Microbial community structure in forest soils treated with a fire retardant. Biol. Fertil. Soils, 42, 465.
74.
BasantaM. R. (2002) biochemical properties of forest soils as affected by a fire retardant. Biol. Fertil. Soils, 36, 377.
75.
Kay-ShoemakerJ. L. (1998) polyacrylamide as an organic nitrogen source for soil microorganisms with potential effects on inorganic soil nitrogen in agricultural soil. Soil Biol. Biochem., 30, 1045.
76.
HollimanP. J. (2005) Model and field studies of the degradation of cross-linked polyacrylamide gels used during the revegetation of slate waste. Sci. Total Environ., 336, 13.
77.
SutherlandG. R. J. (1997) Biodegradation of cross-linked acrylic polymers by a white-rot fungus. Environ. Sci. Pollut. Res., 4, 16.
78.
StahlJ. D. (2000) Biodegradation of superabsorbent polymers in soil. Environ. Sci. Pollut. Res., 7, 83.
