Matrix-based fertilizers (MBFs) are comprised inorganic N and P in compounds that are relatively loosely bound to more tightly bound in fertilizer formulations combined with mixtures of Al2(SO4)3●3H2O and/or Fe2(SO4)3●3H2O plus the high ionic exchange compounds cellulose and lignin. The MBFs were tested for their efficacy to reduce Escherichia coli and Enterococcus spp. and nutrients in leachate and soil after dairy manure application. One day after the first 15 Mg ha-1 dairy manure application, E. coli numbers were greater in leachate from control columns than in leachate from columns receiving MBFs. After three 15 Mg ha-1 dairy manure applications, E. coli and Enterococcus spp. numbers in leachates were not consistently different between columns receiving MBFs and controls. After a massive amount (three separate 15 Mg ha-1 applications) of dairy manure we did not find a breakthrough point for nutrients. In a separate experiment MBFs leached from 5 to 30 times less metolachlor and from 8 to 2678 times les diazinon than the untreated controls. The improved MBF matrix may potentially reduce fertilizer application rates and costs by enhancing the supply of nutrients from nutrient-bearing (polluted) surface waters.

Fresh water quality affects nearly every aspect of every ecosystem on earth as well as the human activity it supports. Ongoing degradation of freshwater ecosystems poses a serious threat to both ecosystem function and human health (Akpor and Munchie, 2011; Black et al., 2011). The amount of N and P deposited into surface waters has drastically increased over the past decade (Akpor and Munchie, 2011; Black et al., 2011; USEPA, 2009). There is urgent need for cost-effective action (Batz et al, 2011). Most federal and state regulations fail to adequately address non-point source pollution, which contributes massive nutrient loads to both surface and ground waters. Nitrogen and P pollution has the potential to become one of the most costly and challenging environmental problems in the 21st century. The Urgent Call to Action: Report of the State-USEPA Nutrients Innovations Task Group, found that 50% of U.S. streams have medium to high concentrations of N and P, 78% of coastal waters exhibit eutrophication (USEPA, 2009).  The incidence of harmful algal blooms in lakes, streams and ocean coastal waters has dramatically increased in recent years. Transport of N and P from both urban and agricultural activities to surface waters has been linked to eutrophication in fresh and marine waters (Akpor and Munchie, 2011; Hudnell, 2010). Eutrophication is widespread and rapidly expanding in fresh waters throughout the world and accounts for about 50% of the impaired lake area and 60% of the impaired rivers in the U.S. (Black et al., 2011). Excess N and P in freshwater can lead to excessive algal production, especially cyanobacteria (Leigh et al., 2010). Algal blooms deplete oxygen in freshwater causing a wide range of aquatic problems including production of algal toxins (i.e., cyanotoxins), benthic invertebrate toxicity, fish kills, stock deaths, and often human illness (Akpor and Munchie, 2011; Hudnell, 2010). Increasing conversion of native lands to agriculture has increased the land area receiving fertilizer, contributing to N and P pollution of surface waters. Nutrient pollution of U.S. freshwater carries potential cost risks of $2.2 to $4.6 billion annually (Dodds, et al., 2009). Current practices and control strategies do not adequately support public health and protect the environment. Nutrient pollution of our nation’s waters has the potential to become one of the costliest, most difficult environmental problems in the 21st century (USEPA, 2009). Current efforts to control nutrients have been inadequate at both a state and national scale. As the U.S. population expands, nutrient pollution from storm water runoff, manure discharges, agricultural livestock activities, and row-crop runoff is expected to increase (USEPA, 2009).

The Use of Manure for Fertilization:

Manure is used widely as a crop fertilizer because it contains N, P and K, and manure can increase soil organic matter and increase water-holding capacity. Manure is commonly transported from animal confinement and manure storage facilities and spread or incorporated into the soil. Manure is a partial substitute for commercial fertilizers, whose prices rose in recent years along with prices for other products derived from fossil fuels and minerals (MacDonald et al., 2009). Nitrogenous commercial fertilizer prices doubled between 2000 and 2007, and then rose again by 62 % between December of 2007 and September of 2008. Phosphorus fertilizer prices rose by 115 % between 2000 and 2007, and then rose by 177 % between December 2007, and September 2008.  Higher commercial fertilizer prices are making manure fertilizers more attractive (MacDonald et al., 2009; Maguire, et al., 2011). Opportunities for widespread manure substitution are limited because manure can be costly to transport for even short distances, and some crops are far from sources of manure production. Furthermore, manure may not have the precise combination of nutrients needed for specific crops and fields (Maguire, et al., 2011).

On average a broiler chicken produces 5 kg of manure, with 0.54 g of N, 16 g of P, and 31 g of K, in the seven weeks that it is fed. A large-scale operation can produce 600,000 broilers in a year (MacDonald et al., 2009). With 32,658 kg of N in the 3,000 metric tons (mt) of manure, a producer would need as much as 233 ha-1 of corn at the application rates noted above. Many broiler operations are specialized, with no crop production, and very few grow that many acres of any crop (USEPA. 2003; MacDonald et al., 2009). But broiler litter is relatively dry and thereby less costly to transport, and its high nutrient content gives it value. As a result, most litter is removed from the operation and spread on other farms. With most production in the South, broiler litter is used on crops like cotton and peanuts, and on Bermuda grass (MacDonald et al., 2009; MacDonald and McBride, 2009). 

A large cattle feedlot might fatten 35,000 cattle for slaughter. Nearby farms incorporate this manure or compost into the soil for fertilizer. Approximately 40 % of U.S. broiler production, and 45 % of total poultry production, occurs on farms with no crop area. Beef cattle produce less manure than dairy cows because the steer will not spend a full year in a feedlot (MacDonald et al., 2009; MacDonald and McBride, 2009). The average large feedlot produces almost 156,520 metric tons of manure each year, with 873,160 kg of N, 116,119 kg P, and 603,275 kg of K (MacDonald and McBride, 2009). A feedlot of that size, with that amount of N, would need to find over 6,070 ha-1 of corn for utilization of the N produced, or a greater area for other crops. Substantial quantities of manure solids must still be moved to farm land and tilled into the soil. The manure is best disposed of by applying it to fields to meet P demand, with application of additional mineral fertilizer N to meet crop N demand. Manure and mineral fertilizers are complementary, not competitive (MacDonald and McBride, 2009; Maguire, et al., 2011). 

Manures are bulky, expensive to transport, contain pathogenic microorganisms, and antibiotics. It is more difficult to effectively utilize the nutrients contained in animal manure than those contained in mineral fertilizers. The N and P content of manure varies between and within livestock species and with food type and quality given to each animal (Maguire, et al., 2011). The nutrient concentrations in manure rarely match what is necessary for maximum crop growth and yield. Since manure N occurs in inorganic and organic forms, N mineralization depends on the temperature and moisture content of the manure and the microbial community (Bradford et al., 2008). When manure application rates match crop P uptake, the volume of raw manure that can be applied per land area is generally insufficient to meet crop N requirements because the N:P ratio is lower in manure than in crops. Therefore, additional N must be applied to gain the most efficient use of manure nutrients to not only maximize crop yield and quality but also minimize nutrient leaching into surface and ground waters (Bittman et al., 2011).

Environmental and Human Health Risks:

Manure can also pose environmental and human health risks. Manure constituents (nutrients and pathogens) can be transmitted from cropland to surface waters through surface runoff and via percolation to ground waters (Bradford and Segal, 2009; Lewis et al., 2010; Entry, et al., 2010). Industrialized livestock production concentrates manure on limited areas, some producers apply manure at intensities in excess of crops needs. Farmers store manure in pits and lagoons, posing environmental risks from seepage and / or flooding (Bradford et al., 2008). Federal and state governments require livestock production units to have nutrient management plans, which impose an additional cost on confined animal feeding operations (CAFOs).  These new regulations mandate manure to be applied relative to crop nutrient demand (MacDonald and McBride, 2009). A dairy cow produces about 68 kg of manure d-1, which is about 24,493 kg of manure annually, including 150 kg of N, 25 kg of P, and 16 kg of K.  If N were applied to corn at a rate of 140 kg ha-1, the farm would need 1.1 ha-1 of corn to absorb each cow’s excreted manure (MacDonald et al., 2009). Dairy farmers rotate corn with alfalfa and other forage crops and fertilize them with manure. Unlike corn, most crops take up fewer nutrients than corn and, therefore, have greater land requirements to absorb each cow’s as-excreted manure (USEPA. 2003; MacDonald et al., 2009). These estimates are maximums, assuming no volatilization from manure occurs. As wet manure dries, some nutrients volatilize—N, for example, becomes airborne NH3. Because volatilization reduces the amounts of nutrients remaining in stored manure, it also reduces the amount of farm land needed for spreading manure at agronomic rates (MacDonald et al., 2009).

Environmental Problems:

Transport of N and P from agricultural soils to surface waters has been linked to eutrophication in fresh water and estuaries (Daniel et al., 1998; Bush and Austin, 2001; Broesch et al., 2001). Eutrophication is widespread and rapidly expanding in fresh surface waters and coastal seas of the developed world.  Eutrophication accounts for about 50% of the impaired lake area and 60% of the impaired rivers in the United States. It is also the most widespread pollution problem in estuaries (Bricker et al., 1999). In most lakes, streams and coastal ecosystems, N is the element most limiting to production of plant material such as algae. Algal blooms cloud the water and block sunlight, causing native underwater flora to die contributing to a wide range of aquatic problems including summer fish kills, foul odors, and unpalatable tastes in drinking water (Zimmerman and Canuel, 2000). Native underwater flora provide food, shelter and spawning and nursery habitat for aquatic fauna. When algae die and decompose, oxygen is depleted, suffocating aquatic fauna.  Phosphorus is also an essential element that contributes to both freshwater and coastal eutrophication. The incidence of harmful algal blooms in lakes, streams and coastal oceans has dramatically increased in recent years (Bricker et al., 1999). This increase is linked to eutrophication and other factors, such as changes in aquatic food webs that may increase decomposition and nutrient recycling or reduce populations of algae-grazing fish. Increasing conversion of native lands to agriculture or development has increased the land area receiving fertilizer and contributes to N and P pollution of surface waters.

Nitrogen and P concentrations were higher in agricultural streams than in streams draining urban, mixed land use, or undeveloped areas. Nitrogen concentrations in streams were highest in areas where fertilizer and manure applications were elevated due to intensive crop production (Dubrovsky and Hamilton, 2010). Nutrient input to streams can be increased in areas where subsurface tile drains soils have been installed. Total N concentrations were lower in urban streams than in agricultural streams however, some of the highest N concentrations in urban streams were downstream of manure water-treatment facilities. Total P concentrations were highest in streams in agricultural and urban areas and as is the case with N, high P concentrations occur in areas associated with high applications of fertilizers and manure (Delgado and Follett 2011). Urban sources may include treated manure water effluent and septic-system drainage, as well as runoff from lawns, golf courses, and construction sites. The amounts of N and P in stream flow increased with increase nutrient inputs from nonpoint sources. Phosphorus is less soluble and mobile than N and thus, P yields are lower than N yields for most streams.

Nutrients in Groundwater:

Nitrate (NO3) exceeded background concentrations in 64 % of shallow wells in agricultural and urban areas. Other nutrient concentrations in groundwater were not significantly greater than background concentrations. Concentrations of NO3 in groundwater were highest in shallow wells in agricultural areas that are associated with high fertilizer and manure applications. Nitrate concentrations were lowest in shallow wells in urban areas and in deep wells in major aquifers. The NO3 in shallow aquifers depends on groundwater age and geochemical conditions that govern NO3 concentrations in groundwater. Groundwater contributions of nutrients to streams can be significant. At least one-third of the total annual load of NO3 in two-thirds of 148 streams studied across the U.S. was derived from base flow, which was essentially from groundwater (Dubrovsky and Hamilton, 2010). Groundwater contributes significant amounts of dissolved P to streams particularly where natural sources of P are upstream. Nutrients also can be removed by plants in the riparian zone. In lakes and streams that are at high risk for agricultural input of nutrients and pesticides, crop-management practices designed to reduce or slow the movement of overland flow to streams are essential. Improvements in water quality as a result of reductions in nutrient inputs on the land may not be apparent in streams for decades because of the slow rate of groundwater movement from the land surface through the subsurface to streams (Daroub et al., 2009; Lang et al. 2010).

Materials and Methods:

Current Fertilizer Technology:

Agricultural operations fertilize crops at rates recommended for maximum growth or yield. In addition, fertilizers vary widely in solubility, and lose different amounts of N and P to leaching when applied to varying soil types (Shober and Sims, 2007). Controlled-release fertilizers (CRFs) and slow-release fertilizers (SRFs) are designed to reduce fertilizer losses to ground water and runoff. Nutrient leaching from CRFs is reduced via organic or inorganic coatings around a core of soluble inorganic fertilizer; the coatings slowly degrade, resulting in eventual acceleration of nutrient release. SRFs are composed of non-coated urea-aldehyde and inorganic resins that release nutrients when water flows through sulfur aldehydes and inorganic resins. SRFs release nutrients in a slow but uncontrolled manner. When SRFs are applied to the soil, the water in the soil enters the SRF granule through micropores, dissolving the nutrients and releasing them into the soil. SRF and CRF release rates are hypothesized to not be influenced by microbiological decomposition, soil moisture, soil type or pH. However, release of nutrients from SRFs and CRFs depends on granule quality. A typical population of CRF granules consists of three types of coatings: 1) damaged coatings with cracks or damaged coatings whose cracks were sealed with wax, 2) intact coatings and 3) thick coatings (Shaviv, 2000). A typical population of SRF granules may have the same problems as CRF granules. The SRF granule may have 1) overly large micropores allowing water into the granule releasing a large amount of nutrients too quickly, 2) the correct micropore size allowing the granule to release the desired amount of nutrients at the desired time, and 3) micropores that are too small inhibiting water flow into the granule and inhibiting or preventing release of nutrients into the soil. “Failure release” is when damaged SRFs or CRFs immediately release nutrients when brought in contact with water. The proportion of the CRF and SRF nutrients that are not released into the soil over the growing season is termed “locked-off” (Shaviv, 2000). A population of CRF or SRF granules may consist of more than one third “failure-release” granules where nutrients are immediately released and about one third “locked-off” granules (Shaviv, 2000). Therefore, one third or more of the CRF or SRF content may be immediately released as an initial burst after being applied, and about one third may be “locked off” and released long after it is needed by the plant. Even if the controlled release (CRFs) or slow-release-fertilizers (SRFs) were applied at rates to meet crop N and P demand over a growing season and plants grew at their maximum potential, it would be difficult for the plants to take up enough N and P to prevent leaching. The problem is made more severe because agricultural managers and home owners often apply nutrients in quantities exceeding plant requirements (Hart et al., 2003). The concentration of N and P in water, necessary for eutrophication is an order of magnitude smaller than the soil N and P concentration necessary for plant growth (Daniel, et al., 1998). The MBFs were developed with ionic bonding and as such do not have shell coatings, which must be dependent on specified moisture or temperature ranges.

Matrix-Based Fertilizers:

The MBFs cover a range of inorganic N and P in compounds that are relatively loosely bound to more tightly bound in fertilizer formulations combined with mixtures of Al2(SO4)3●3H2O and/or Fe2(SO4)3●3H2O plus the high ionic exchange compounds cellulose and lignin (Figure 1)

Figure 1. A simplified diagram of Matrix Based Fertilizers. MBFs are comprised of cellulose having ionic binding sites and degrades at a moderate rate in soil, lignin having strong ionic binding sites and is recalcitrant to decomposition in soil. Aluminum sulfate (Al₂(SO₄)₃●3H₂O) and iron sulfate (Fe₂(SO₄)₃●3H₂O), which have strong ionic binding sites and are readily soluble, are attached to the cellulose-lignin base. Cellulose and lignin are incorporated into the matrix because of their high concentration of ionic exchange sites and their decomposition characteristics. The MBFs contain a range of inorganic N and P in compounds that are relatively loosely bound to more tightly bound in fertilizer formulations. The MBFs can be made to bind inorganic nutrients relatively tightly or loosely by altering the ratio of lignin - (Al₂(SO₄)₃●3H₂O) - Fe₂(SO₄)₃●3H₂O to other constituents in the formulation.

After the starch-cellulose-lignin matrix with Al2(SO4)3●3H2O and/or Fe2(SO4)3 3H2O is applied to soil, soil microorganisms degrade the starch in the matrix comparatively rapidly and will lose some ionic exchange sites. Cellulose which degrades less rapidly than starch but more rapidly than lignin, is expected to retain most of its ionic exchange sites for about a year in most soil environments (Donnelly et al., 1990). Lignin degrades slower than starch or cellulose and is expected to retain its ionic exchange sites for several years in most soil environments (Donnelly et al., 1990). The MBF formulations can be made to bind inorganic nutrients, pesticides, and pathogenic bacteria relatively tightly or loosely by altering the ratio of Al2(SO4)3●3H2O and Fe2(SO4)3● 3H2O to other constituents in the formulation. When the matrix is applied to soil, microbes degrade cellulose more rapidly than lignin which retains its ionic exchange sites for a longer time than cellulose (Donnelly et al.,1990). Nutrients bound to the Al2(SO4)3●3H2O and Fe2(SO4)3● 3H2O - cellulose - lignin matrix become slowly available to plants as the organic components in the matrix degrade. MBF formulations can contain a range of N and P concentrations and availabilities to tailor the MBF to a specific crop nutrient demand. The initial MBFs were designed to provide nutrients to horticultural plants and turf grass and are being commercialized by Nutrigrown LLC. We found that Osmocote® 14-14-14 a slow release fertilizer (SRF), combined with Al(SO4)3 and Fe(SO4)3 leached 78-84% more NH4, 58-78% more TP, 20-30% more TRP and 61-77% more than MBFs (Entry and Sojka, 2007; 2008). The SRF treatment leached 34% less NO3, than MBF 3. Total plant weight did not differ among fertilizer treatments. Arbuscular mycorrhizal infection did not differ among plants receiving SRF and MBFs. Entry and Sojka (2007) found that in three soil textures the SRF leachate contained a higher amount of NH4, NO3 and TP than leachate from MBFs. However, wheat plants growing in soils receiving SRF had greater shoot, root and total biomass than all MBFs. Entry and Sojka (2008) found that SRF leachate contained a greater amount of NO3, NH4, DRP and TP than leachate from MBF1 and MBF3 regardless of fertilizer rate or whether MBFs were applied as pellets, bands or broadcast. St Augustine grass growing in soils receiving MBF1 and MBF3 decreased shoot biomass by 49 to 56% and decreased total biomass by 33 to 46% compared to grass receiving SRF. In greenhouse column studies Entry and Sojka (2008) tested the efficacy of MBFs with and without additional Avail®, a commercial release fertilizer (SRF), to improve Kentucky bluegrass, (Poa pratensis L.) growth while reducing NH4, NO3, dissolved reactive phosphorus (DRP), total reactive phosphorus (TRP), and total phosphorus (TP), compared to the commercial fertilizers. They found that the amount of NO3 and NH4 leached was greater from columns receiving Polyon®, ESN® fertilizers and the MBF1. The MBF1+ Avail® or MBF3+Avail® leached 64-68% less NO3- than Polyon® (43-0-0) and ESN® (46-0-0) and 73-76% less TDP and TP than Avail® (10-34-0). Shoot and root biomass were greater when plants received the Avail®, MBF1+Avail® and MBF3+Avail® than the other fertilizer treatments. Shoot biomass was greater when plants received the MBF1 and MBF3 high rate than the MBF1 and MBF3 low rate, Polyon® and ESN®. 

The MBFs were then tested for their efficacy to reduce E. coli and Enterococcus spp. and nutrients in leachate and soil after dairy manure application (Entry and Sojka, 2007; 2008; 2009; Entry et al., 2010). One day after the first 15 Mg ha-1 dairy manure application, E. coli numbers were greater in leachate from control columns than in leachate from columns receiving MBFs. After three 15 Mg ha-1 dairy manure applications, E. coli and Enterococcus spp. numbers in leachates were not consistently different between columns receiving MBFs and controls. Lignin reduces E. coli and Enterococcus spp. survival in manure amended soils where application rates were not excessive (Baurhoo et al., 2008). We found a breakthrough point for E. coli and Enterococcus spp. at or near 15 Mg ha-1 dairy manure application (Entry et al., 2010). Microbial cells have both positive and negative surface charges and can be bound to the MBF matrix reducing leaching or runoff. When MBFs were applied to the soil, the total amount of DRP, TP, NH4, and NO3 in leachate was lower than in the control columns. After a massive amount (three separate 15 Mg ha-1 applications) of dairy manure we did not find a breakthrough point for nutrients.

The widespread presence of pesticides and their degradation products in ground water of the USA has been documented in many large- and small-scale investigations (Hallberg, 1989; Barbash and Resek, 1996; Gilliom et al., 2006). Leaching through soil has been identified as a major pathway for introduction of agrochemicals into groundwater (Flury, 1996). The intensity of pesticide use is a significant predictor of pesticide detection in ground water (Barbash et al., 1999), but soil permeability, available water capacity, organic carbon content, and land management practices are also important controlling factors (Barbash and Resek, 1996). Evidence has established that nonuniform or preferential transport in the subsurface occurs in a wide variety of hydrogeologic settings (Barbash and Resek, 1996; Flury, 1996; McMahon et al., 2006). One consequence of this phenomenon is that substantial amounts of pesticides and their degradates move more rapidly through preferential pathways in the unsaturated zone in response to individual recharge events, bypassing most of the soil matrix (Barbash and Resek, 1996).

The MBFs were also tested for their efficacy to reduce 2, 4-D, metolachlor, thiophanate methyl, carbaryl, diazinon and malithion leaching in soil columns (Entry and Sojka, 2012).  Pesticide leaching through soil has been identified as a major cause for the occurrence of these chemicals in surface and ground water. After 21 days 2, 4-D, thiophanate methyl, carbaryl, and malathion did not leach is sufficient quantities to determine if the MBFs reduced leaching compared to the control and the slow release fertilizer Polyon® (Entry and Sojka, 2012). The control and Polyon® treatment leached from 5 to 30 times more metolachlor than the MBFs. The control treatment leached from 2 to 72 times more diazinon than the MBFs. The Polyon® treatment leached from 8 to 2678 times more diazinon than the MBFs. The MBFs allow compounds with both anionic and cationic charges to bind with their Al2(SO4)3●3H2O and/or Fe2(SO4)3●3H2O-lignin-cellulose matrix components. We postulate that when pesticides are added to soil amended with MBFs the metolachlor and diazinon bind to the Al2(SO4)3●3H2O and/or Fe2(SO4)3 3H2O-starch- cellulose-lignin matrix components of the fertilizer, thereby substantially reducing leaching.  The new MBFs may allow pesticides with both anionic and cationic charges to bind with the Al2(SO4)3●3H2O and/or Fe2(SO4)3 3H2O -lignin-cellulose matrix. We postulate that when pesticides are added to the soil, MBFs bind the pesticides to the Al2(SO4)3●3H2O and/or Fe2(SO4)3 3H2O-starch- cellulose-lignin matrix, thereby substantially reducing leaching. Pesticide leaching is expected to be controlled to a large degree by varying the relative amounts of starch-cellulose- lignin matrix with Al2(SO4)3●3H2O /or Fe2(SO4)3 3H2O in the mixture. Improved pesticide retention technology via use of MBFs cannot substitute fully for adhering to sound land management practices, but could be potentially beneficial. Although further research is necessary MBFs have the potential to limit both nutrient and some pesticides leaching from agricultural fields.

Although further greenhouse and field testing are necessary, results of this and previously published initial investigations are promising. Cost estimates of these MBFs have been calculated to be $0.03-0.08 kg-1 above the cost of conventional fertilizers. One of the main goals of future research should be to reduce the cost of MBF production. MBFs initially may be economically feasible for use by homeowners on their lawns, turf grass or golf course managers and growers of high value agricultural crops. The MBF could prove particularly important for soils whose surface or internal drainage affects water quality of sensitive ecosystems.