«A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Crop, Soil, and Environmental Sciences ...»
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Urea-TSP 6.8 de 283 d tPoultry litter + urea (PLU), PLU + dicyandiamide (DCD) (PLUDCD), PLU + biosolids (PLUB), PLUB + DCD (PLUBDCD), lignosulfonate (LS), urea formaldehyde (UF), water (W), and triple super phosphate (TSP).
|Means followed by the same letter are not significantly different at;?0.10 within each column.
Poultry litter (PL) and municipal biosolids (BS) are valuable fertilizer sources due to significant nutrient concentrations. However, if applied on a P basis, low N:P ratios coupled with low total N availability provide inadequate fertilization. Nitrogen fortification is needed to increase PL and BS utility as agronomic and horticultural fertilizers. The objective of this study was to model N release characteristics from Nfortified PL and BS granular fertilizers containing additives. A 2 x 2 x 3 8 factorial arrangement of granules with and without BS, with and without a nitrification inhibitor [dicyandiamide (DCD)] and bound with lignosulfonate, urea formaldehyde, or water was tested in a 112 d non-leached aerobic incubation study. The investigation was conducted on a silt loam soil in a randomized complete block design. Extraction procedures for inorganic N were conducted at 0, 3, 7, 14, 28, 56, 84, and 112 d. Granular product mineralization patterns were also compared to fresh PL, ground PL, BS, Milorganite, DCD, and urea treatments. Averaged over the entire incubation period, granulated products had 71.5% of N mineralized while urea, BS and PL averaged 80.5, 16.8, and 36.7%, respectively. Granules containing DCD had 6.7% less N mineralization and suppressed nitrification in granular treatments until 56 d after fertilizer application.
Binding agent and BS additions had no statistical impact on NH4-N or NO3-N soil concentrations. Nitrogen-fortified PL and BS granules may improve N efficiency over fresh PL and BS due to more N availability and less potential environmental N losses over a growing season.
BS, biosolids; DCD, dicyandiamide; epm, evolutions per minute; LS, lignosulfonate;
LSD, least significant difference; PL, poultry litter; PLU, PL + urea; PLUB, PLU + BS;
PLUBDCD, PLUB + DCD; PLUDCD, PLU + DCD; UF, urea formaldehyde; W, water.
Poultry litter is a proven fertilizer and possesses restorative qualities when applied to soils that are severely eroded or precision leveled (Shortall and Liebhardt, 1975; Bitzer and Sims, 1988; Sistani et al., 1988; Miller et al., 1990; Miller et al., 1991; Edwards and Daniel, 1992; Cooperband et al., 2002; Brye et al., 2005; Mitchell and Tu, 2005).
Biosolids, municipal sewage sludge treated to land application standards, were first used in published fertilizer research in 1924 and have been successfully used in production systems since (Reynolds, 1926; Hinesly et al., 1972; Gilmour et al., 2003). While the utility of using PL and BS in agronomic settings is well established, limitations exist with large scale use in its unaltered form. Both materials have low N:P ratios, requiring N fortification for agronomic acceptability when applied on a P basis (Edwards and Daniel, 1992). The unaltered material is also too bulky and irregular for practical and efficient land spreading, has an inconsistent analysis, odor, and a negative stigma (Mitchell and Tu, 2005). Formulating PL and BS into value added fertilizer sources will allow them to be more competitive in the market; thereby, increasing use and decreasing environmental concerns in nutrient surplus watersheds.
Poultry litter contains approximately 35 g total N kg"1, with most N in the organic form (-70%) and the remainder (30%) residing in inorganic fractions (Sims, 1986; Sims, 1987; Westerman et al., 1987). Pratt (1973) proposed that 90% of the PL organic fraction
approximately 69% organic N mineralization. Similar to PL, USEPA (1995) reported mean BS values of 39 g total N kg"1 with 18% of total N present as inorganic N. Gilmour and Skinner (1999) found that 40% of BS total N was available during the growing season during incubation and field trials with non-dried BS. However, processing PL and BS into fertilizers changes nutrient release characteristics over fresh ingredients. For instance, Hadas and coworkers (1983) showed more inorganic N release from pelletized litter compared to fresh PL while greenhouse studies by Cox (1995) indicated lower N mineralization rates from pelletized BS compared to fresh BS. Grinding PL for granulation purposes may also impact mineralization since fine particles have larger surface area for microbial activity compared to fresh PL (Hadas et al., 1983; Cabrera, 1994).
Additives to granulated PL and BS products may enhance N use efficiency by resisting N transformations to NO3-N or by physically releasing N at slower rates during the growing season. Several studies indicated that DCD, a nitrification inhibitor, can effectively reduce N loss in agronomic systems and increase plant N assimilation and yield (Cowie, 1918; Ashworth and Rodgers, 1981; Norman et. al., 1988; Norman et. al.
1989; Reeves and Touchton, 1989). Adding different fertilizer additives that double as a binding agent may also change granule N release characteristics. For instance, urea formaldehyde is commonly used in slow release fertilizers and was shown to release inorganic N over several weeks (Christianson et al., 1988; Mikkelsen et al., 1994). Urea formaldehyde is also used as a binder for forming ground organic material into stable pellets (Tabil et al., 1997). Lignosulfonate used as a binding agent will not offer slow
fertilizer application (Tabil et al., 1997). Reducing surface area of finely ground PL by formulating materials into granules may decrease overall PL and BS mineralization rates (Hadasetal., 1983).
Few research studies concerning fortification of PL and BS fertilizers with products that change N mineralization and transformation dynamics have been conducted. The objective of this study was to establish inorganic N release patterns from N-fortified PL and BS fertilizers containing different additives using a silt loam soil under non-leached aerobic conditions.
A non-leached aerobic incubation study was conducted with a Dewitt silt loam (Fine, smectitic, thermic Typic Albaqualf) to evaluate N mineralization characteristics of N-fortified PL and BS granular fertilizers. Selected soil and fertilizer chemical properties are presented in Table 6.1. Dicyandiamide was included in certain treatments at a 1:10 DCD-N:total N ratio. Total granular fertilizer C and N concentrations were estimated by dry combustion using a LECO CN2000 (LECO Corp., St. Joseph, MI 49085) (Colombo and Giazzi, 1982). Inorganic N was extracted by shaking 3 g of fertilizer with 30 mL 2 M KC1 at 200 evolutions per minute (epm) for 2 h (Hoskins et al., 2003).
Nitrogen fertilizers were applied at a rate of 330 mg N kg soil" to allow incorporation of several whole fertilizer granules. Fertilizers were mixed with 119 g "asis" soil (100 g on dry weight basis) in 1 L polyethylene wide mouth bottles. Double deionized water was added to each bottle to raise moisture content to 60% water filled
1984). Bottle weights were taken so water concentration could be corrected on a weekly basis. Uncapped bottles were placed in 100% humidity chambers and incubated at 25°C for 0, 3, 7, 14, 28, 56, 84, and 112 d. At each sampling interval, 1 incubation vessel per replication per treatment was sacrificed and approximately 10 g soil was subsampled from each bottle for moisture determination. Inorganic N from the remaining soil was extracted by adding 900 mL 2 MKC1 to the bottle and shaking for 1 h at 200 epm (Mulvaney, 1996). The suspension was allowed to settle for 30 min and supernatant was decanted and filtered through Whatman 42 filter paper (Whatman pic, Middlesex, UK).
Ammonium-N and NO3-N were determined using continuous flow analysis on a Sanp us System (SKALAR Inc., Norcross, GA 30071).
Carbon to N ratios for the bulk soil and fertilizers was calculated by dividing total C concentration by total N concentration. For the incubation study, unamended control soil inorganic N concentrations at each time interval (Fig. 6.1) were subtracted from the total amount extracted (soil + fertilizer inorganic N) to achieve fertilizer inorganic N mineralized. Fertilizer inorganic N mineralized was divided by total N applied to achieve a percentage of available total N.
Incubations were conducted in a randomized complete block design with treatments blocked per incubator. Each of 3 blocks served as a replication and was analyzed as a random effect. Nitrogen sources used were arranged i n a 2 x 2 x 3 x 8 factorial arrangement with the following treatments: with and without BS; with and
incubated for 0, 3, 7,14, 28, 56, 84, and 112 d. The 12 N-fortified PL and BS fertilizer combinations were also compared to BS, DCD, fresh PL, ground PL, Milorganite, and urea fertilizer N sources in a randomized complete block design. Data were analyzed using analysis of variance conducted with the General Linear Model procedure (PROC GLM) in SAS v. 9.1 (SAS, 2003) at the 5% significance level. Fisher's protected least significant difference (LSD) test was used to separate significant means (Steele and Torrie, 1980).
Available N mineralized from dry ingredients used to make our granular fertilizers and for fertilizers used as comparison are presented in Fig. 6.2. Urea had 98.5% of N represented as inorganic fractions 7 d after application. Urea quickly undergoes hydrolysis if sufficient urease enzymes are present in conjunction with desirable environmental conditions (Moyo et al, 1989; Han et al., 2004). Recovery of urea-N as inorganic N had decreased to 73 and 57% N availability for 84 and 112 d, respectively (Fig. 6.2). Norman and coworkers (1987) suggested N immobilization, denitrification and/or volatilization as the main inorganic N loss pathways during aerobic incubations on silt loam soils. Fresh PL had 38.6% of total N as inorganic fractions 7 d after application;