Reducing of Nitrogen Problem in Australia - Case Study Example

Background Nitrogen is essential for successful production of crops as it plays a key role in photosynthesis. Due to continuous farming for many decades, nitrogen as a vital nutrient has often been depleted and it must be added to ensure optimal growth of plant. Thus, modern farming practices require addition of nitrogen in various ways such as nitrogen fertilisers, manure and sewage sludge among others. When soluble forms of nitrogen are accumulated in water, in particular, nitrate, they can be detrimental. This is because high concentrations in surface and groundwater lead to various health and environmental consequences (Dillon, 1997). After the Second World War, agriculture has been modernised gradually and farming practices has been becoming more extensive. Various changes had consequences in regard to the quality of water. First, due to ploughing large areas of virgin grasslands, there was oxidation of nitrogen in organic matter. Secondly, in 1950s, significant increase in application of nitrogenous fertilisers began. Due to such changes, the amount of nitrate leached from the soil due to infiltration from rainfall and as a result, gradual increase in concentration of nitrate became evident. As farmers continue to intensify production in order to respond t guaranteed markets, they apply more fertilisers, as well as other inputs such as pesticides to their farms in order to increase their yields. Due to increase in prices that farmers received from farm products, farmers could also increase the use of fertilisers economically. Thus, application of fertilisers increased more significantly in different states (Dana et al, 2010). Above background concentrations of nitrates in groundwater has been reported throughout the world and the issue has been identified as one of the most widespread and common chemical contaminant in groundwater. In early 80s, concentrations between 0.45 and 2.0 mg/L in ground waters were reported in USA and Europe (Hallberg, 1989) and 1.15 to 2.3 mg/L in Australia (Lawrence, 1983). Since then, there has been significant contamination of drinking water supplies. This also led to management of groundwater, for instance, identification of zones for protection of groundwater around wellheads in UK which are meant for minimising contamination of groundwater by nitrates, as well as other contaminants, in particular those associated with agricultural practices. Nitrogen has also been identified as a common problem in island settings associated with little wellhead protection of groundwater resource (Dillon, 1997). In Australia, extensive occurrence of nitrate above ground levels was also reported. The main activities in Australia that generate sources of nitrate in Australia which later lead to reduction of water quality include natural sources (such as rainfall and degradation of natural vegetation), human activities (such as cultivation, influence of clearing on natural vegetation, and tillage of soils), and human introduces sources (such as farm animal wastes, fertilisers, human waste treatment, general urban development, industrial wastes, etc) (LWRRDC, 1999). Nitrate problem When in water, nitrates are pollutants and agriculture is the main source of pollution. As plants require nitrates only in limited quantity, excess application of manure or fertiliser leads to environmental problems. Excess nitrate reach surface or groundwater by leaching through the soil or running off the land. The rate of leaching is affected by various factors such as the amount of rainfall, soil type, and type of plant cover. Nitrates already in soils have direct consequences and potential for further damage as it may take quite a number of years before leaching nitrates are detected in groundwater supplies. Thus, the severity of contamination of groundwater is not only reflected in current water supplies but also in future (Ballard, & Keating, 1994). Excess nitrates also play a significant role in surface water through eutrophication, which is referred to as an overabundance of nutrients. Eutrophication affects both fresh and salt waters which often result to excess growth of algae. Growth of algae in fresh water is associated with the level of phosphorous and nitrates. Excessive use of phosphate and nitrate fertilisers leads to eutrophication in surface waters in various regions. As a result, algal blooms causes disturbance of the levels of oxygen leading to various consequences for ecosystem in general and uses of water for drinking and recreation. Increased levels of nitrates have also led to eutrophication in open seas and coastal waters with algae blooms characteristics. This causes depletion of oxygen which often harms marine life. Harmful marine algae (red or brown tides) release harmful toxins resulting to marine animal mortality (Dana et al, 2010). Strategies for eliminating or reducing N-leaching in farming systems China Management strategies of fertilizer nitrogen include appropriate N application rate and timing N application in harmony with crop demand. Excess nitrate in the soil after the end of cropping is prone to leaching. As a result, limiting inorganic nitrogen at the end of the growing season of the crop and before the establishment of the next crop has been the key to reducing the losses in nitrates. Splitting application of nitrates has been effective in regard to the crop demand where high concentrations of nitrates have been provided in different period of growth and minimisation during the time where risk of leaching is high (Guo, Zhang, Zhang, & Lu, 2006). Soil management strategies include onsite soil nitrates test and tillage. Soil tests on nitrates are important because they provide well guided soil management decisions for agricultural systems to ensure prevention of nitrates leaching; yield and quality are also the ultimate goals. The farmers adopt conventional tillage to manage nitrate in the soil. For instance, although tillage has higher average concentration of nitrates, it have less nitrate leaching losses under continuous corn systems because of its higher capacity in water retention (Dana et al, 2010). Crop management strategies include introducing cover crops, manipulating diversified crop rotation, and managing plant residues. Cover crops are used as scavengers for recovering nitrates leached from other crops and reduce leaching losses in the next crop. For instance, change from continuous growth of corn to diversified crop rotation reduces leaching. Different rooting depths such as barley, winter wheat and cover crops increase N use efficiency thus reducing nitrate leaching (Dana et al, 2010). In addition to nitrogen management, water management strategies unsure that control of leaching more effective. For instance, drip irrigation is preferred in reducing leaching based on efficient water use. United Kingdom The scale of the nitrate problem in United Kingdom is based on the following key strategies for better land management: Reduction in the use of artificial fertilisers Delaying ploughing-in of crop residues Sowing autumn crops early Avoiding bare ground during winter especially by sowing cover crops Managing the disposal of farm carefully In addition, they guarantee better farming practices through directives from the European community that allows identification of water which are or are at the risk of being affected by nitrogen pollution from sources of agriculture. This is referred to as nitrate vulnerable zones (NVZs) where measures are adopted to significantly reduce nitrate leaching from the soil. In regard to aquifers, there are nitrate sensitive areas. Upon the provision of appropriate measures in prevention of leaching into the aquifers, farmers in these areas are also paid due to changing farming practices in order to reduce fertilisers and manure application. This leads to reduction in the amount of nitrate with the potential of leaching from the soil (Ballard, & Keating, 1994). United States of America USA has also made great effort in reducing nitrate in water resources in regard to modern farming systems. They consider various strategies for reducing the loss of nitrates by improving management practices (Ballard, & Keating, 1994). Use of tillage methods to reduce nitrate Use of reduced tillage methods reduces runoff and soil erosion and as well slowing nitrate leaching. These methods are able to slow down the rate at which nitrogen is released from previous crop residue to a later time during summer when the need of nitrogen for the growing crop increases. Changing tillage practices further leads to more reduction in amount of nitrate in the soil which means lower potential of nitrogen problem (Keating et al, 2003). Use of crop rotation to reduce nitrate leaching Adopting farming systems which use corn-soybean rotation leads to efficient use of nitrogen in the soil and in turn reducing nitrate leaching. Based on this farming system, the nitrogen required for corn following soybeans is reduced because there is nitrogen left by soybeans in the soil. Cover crops such as alfalfa have also proved effective in removal of residual nitrate below the rooting system of corn (Ballard, & Keating, 1994). Management of fertiliser and water to reduce nitrate pollution Nitrate accumulation is significantly reduced by dividing the application of fertiliser into various applications instead of applying once. Although subsurface drainage systems are essential in ensuring efficient crop production, drained water that contains nitrates can easily contaminate the surface water. This is addressed by first routing discharge through wetlands from subsurface drains and then to surface streams for significant reduction of movement of nitrate to public waters (Keating et al, 2003). In addition, with improvement of farming systems for the benefit of improving production hence income, risks of nitrate to water resources are also reduced. US ensure continuous control of nitrates in future by ensuring (Ballard, & Keating, 1994): There are site-specific decisions required for every farm due to unique set of inputs and resource that influence management of nitrogen Implementing management decisions that are more site-specific in order to meet the challenge of soil variability so as to ensure least risk on environment and better production. Careful management of the amount and timing of irrigation applications helps in reduction of nitrate loss from fields and reduction of nitrogen enrichment of water resources. The key to reducing the contamination of water resources by nitrate is by use of technology to assist in decisions on the rate of nitrogen fertiliser Encouraging farmers to adopt new technologies that show evidence that a farming system reduces the economic and environmental risks in regard to crop production. Australia Australia has made various efforts in reduction of water and nitrogen loss below the root zone. For instance, potatoes are among the crops grown in Australia the leads to highest rate of loss of nitrogen. However, among the management options for reduction of loss of nitrogen is splitting the application of Nitrogen fertiliser and variation in the rate of application of water. This includes the changing the rate of application by reducing amount of water used (for instance from 26mm to 13mm, where all are within the range of effective irrigation) and applying once the soil water deficit is attained. This leads to reduction of average seasonal drainage as well as reduction of nitrogen loss while maintaining crop yield. In addition, decreasing the top dress rate and basal rate of fertiliser leads to saving in the cost of fertilisers and reduction of the loss of nitrogen while maintaining crop yield (Zhang et al, 2006). Australia also adopts various strategies that reduce the amount of nitrates based on herd and feeding strategies, and soil based strategies. In regard to the management of effluent, the emissions of nitrates are minimised in pastures when the when the effluent is applied to dry soil instead of wet or waterlogged soil. When nitrification inhibitors for urine are applied to the pasture, it reduces nitrous oxide emissions and boosts pasture yield. Reduction of nitrogen in dairy pastures is ensured by providing cattle with supplement containing low protein but high energy. These include cereal grains and maize silage. In regard to soil based strategies, improved drainage leads to reduction in nitrates as well as better growth of pastures (Silva, Cameron, and Hendry, 1999). There also strategies used in regard to Nitrogen fertiliser in agricultural systems. Efficient use of fertiliser can have a significant influence in regard to nitrogen losses, in particular, cropping systems. The aim of farmers in this case is to improve the use of nitrogen fertiliser by plants while considering the factors of climate such as soil drainage and rainfall. Other factors that are put into consideration include seasonal plant growth patterns, selection of appropriate nitrogen fertiliser management in order to optimise the uptake of nitrogen, as well as minimising nitrate leaching losses. In cropping systems, post-harvest management has proved to be essential. The best chance for reduction of nitrogen losses from cropping systems is associated with implementation of management strategies in order to avoid a situation where soil nitrogen is built-up following crop harvest and during fallow periods. This has been enhanced by removing mineralised soil nitrogen by soil bacteria and plants, as well as timely cultivation. This results to minimisation of building-up of mineralised nitrogen (Turpin et al, 1998). Conclusion The problem of nitrates is a challenge throughout the world, but its effect varies according the farming systems and the types of crops available in different countries. However, countries apply almost the same management strategies. This is because t the strategies in every country broadly address application of N fertiliser, nature of soil, types of crops, and water management. In Australia, current farming systems are operating at or near best practice management as they have led to significant reduction or elimination of nitrate leaching as well as maximising dairy and crop production. Their management strategies in regard to reduction of nitrate leaching losses from agricultural systems have shown evidence in targeting four main areas which include management of nitrogen fertiliser, grazing management, and post-harvest management in regard to cropping system as well as the management of the whole system. However, there will always be new challenges and in order to significantly reduce this problem in Australia as well as throughout the world, new strategies and options will need to be developed and tested continuously. References Ballard, R. & Keating, K.M. (1994). Is There an Ocean of Difference? A Comparison of the European Community’s and United States’ Environmental Regulations Protecting Air and Water Quality, Vill. Environmental. Law Journal, 5, 115- 152. Dana, D., Douglas, K., Dan, J., et al. (2002). Nitrogen Management Strategies to Reduce Nitrate Leaching in Tile-Drained Midwestern Soils. Agronomy Journal, 94(1), 153-171 Dillon, P.J. (1997). Groundwater pollution by sanitation on tropical islands. International Hydrological Programme. IHP V, Technical Documents in Hydrology, No 6, UNESCO Project 6.1, SC-97/WS/8, Paris, 34p Guo, M., Li, H., Zhang, Y., Zhang, X. & Lu, A. (2006). Effects of water table and fertilization management on nitrogen loading to groundwater. Agricultural Water Management, 82, 86-98 Hallberg, G.R. (1989). Nitrate in groundwater in the United States. In: Nitrogen Management and Groundwater Protection. Ed. Follett, R.F. Elsevier, Amsterdam, 35–74. Keating, B.A., Carberry, P.C., Hammer, G.L, Probert, M.E, Robertson, M.J, Holzworth, D, Huth, N.I, Hargreaves, J.N.G, Meinke, H, Hochman Z, McLean, G., Verburg, K, Snow, V, Dimes, J.P, Silburn, M, Wang, E, Brown, S, Bristow, K.L, Asseng, S, Chapman, S, McCown, R.L, Freebairn, D.M, Smith, C.J. (2003). An overview of APSIM, A model designed for farming systems simulation. European Journal of Agronomy 18, 267-288. Lawrence, C.R. (1983). Nitrate-rich groundwaters of Australia. Australian Water Resources Council, Technical PaperNo. 79. Australian Government Publishing Service, Canberra. LWRRDC (1999). Contamination of Australian Groundwater Systems with Nitrate’ LWRRDC Occasional Paper 03/99 Silva, R. G., Cameron, K. C., Di, H. J., and Hendry, T. (1999). A lysimeter study of the impact of cow urine, dairy shed effluent and nitrogen fertilizer on drainage water quality. Australian Journal of Soil Research 37, 357-369. Turpin, J. E., Thompson, J. P., Waring, S. A., and MacKenzie, J. (1998). Nitrate and chloride leaching in vertosols for different tillage and stubble practices in fallow grain cropping. Australian Journal of Soil Research 36, 31-44 Zhang, H., Turner, N.C, Poole, M.L, & Simpson, N. (2006). Crop production in the high rainfall zones of southern Australia — potential, constraints and opportunities. Australian Journal of Experimental Agriculture, 46, 1035 - 1049. Read More

The main activities in Australia that generate sources of nitrate in Australia which later lead to reduction of water quality include natural sources (such as rainfall and degradation of natural vegetation), human activities (such as cultivation, influence of clearing on natural vegetation, and tillage of soils), and human introduces sources (such as farm animal wastes, fertilisers, human waste treatment, general urban development, industrial wastes, etc) (LWRRDC, 1999). Nitrate problem When in water, nitrates are pollutants and agriculture is the main source of pollution.

As plants require nitrates only in limited quantity, excess application of manure or fertiliser leads to environmental problems. Excess nitrate reach surface or groundwater by leaching through the soil or running off the land. The rate of leaching is affected by various factors such as the amount of rainfall, soil type, and type of plant cover. Nitrates already in soils have direct consequences and potential for further damage as it may take quite a number of years before leaching nitrates are detected in groundwater supplies.

Thus, the severity of contamination of groundwater is not only reflected in current water supplies but also in future (Ballard, & Keating, 1994). Excess nitrates also play a significant role in surface water through eutrophication, which is referred to as an overabundance of nutrients. Eutrophication affects both fresh and salt waters which often result to excess growth of algae. Growth of algae in fresh water is associated with the level of phosphorous and nitrates. Excessive use of phosphate and nitrate fertilisers leads to eutrophication in surface waters in various regions.

As a result, algal blooms causes disturbance of the levels of oxygen leading to various consequences for ecosystem in general and uses of water for drinking and recreation. Increased levels of nitrates have also led to eutrophication in open seas and coastal waters with algae blooms characteristics. This causes depletion of oxygen which often harms marine life. Harmful marine algae (red or brown tides) release harmful toxins resulting to marine animal mortality (Dana et al, 2010). Strategies for eliminating or reducing N-leaching in farming systems China Management strategies of fertilizer nitrogen include appropriate N application rate and timing N application in harmony with crop demand.

Excess nitrate in the soil after the end of cropping is prone to leaching. As a result, limiting inorganic nitrogen at the end of the growing season of the crop and before the establishment of the next crop has been the key to reducing the losses in nitrates. Splitting application of nitrates has been effective in regard to the crop demand where high concentrations of nitrates have been provided in different period of growth and minimisation during the time where risk of leaching is high (Guo, Zhang, Zhang, & Lu, 2006).

Soil management strategies include onsite soil nitrates test and tillage. Soil tests on nitrates are important because they provide well guided soil management decisions for agricultural systems to ensure prevention of nitrates leaching; yield and quality are also the ultimate goals. The farmers adopt conventional tillage to manage nitrate in the soil. For instance, although tillage has higher average concentration of nitrates, it have less nitrate leaching losses under continuous corn systems because of its higher capacity in water retention (Dana et al, 2010).

Crop management strategies include introducing cover crops, manipulating diversified crop rotation, and managing plant residues. Cover crops are used as scavengers for recovering nitrates leached from other crops and reduce leaching losses in the next crop. For instance, change from continuous growth of corn to diversified crop rotation reduces leaching. Different rooting depths such as barley, winter wheat and cover crops increase N use efficiency thus reducing nitrate leaching (Dana et al, 2010).

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