Urea-ammonium Nitrate Solution Research Articles

Tillage and Fertilizer Effects on Yield, Profitability, and Risk in a Corn‐Wheat‐Potato‐Wheat Rotation

Reduced tillage results in lower production costs and thus may have economic advantages for farmers. However, yield penalties, specific yield risks, or higher nutrient requirements may counteract the positive effects of reduced tillage. This study investigates long‐term tillage effects (moldboard plow, and deep and shallow chisel plow) and their interactions with N fertilizer input on yields and economic performance in a corn (Zea mays L.)‐wheat (Triticum aestivum L.)‐potato (Solanum tuberosum L.)‐wheat rotation in southern Germany. Conventional tillage (CT) and reduced tillage systems provided comparable economic returns. The systems of reduced tillage required higher surface‐dribbled urea ammonium nitrate solution (UAN) fertilizer to corn and potato to be as efficient as the CT system. This may have implications for the overall environmental assessment of reduced tillage systems. For moderate‐ and higher‐risk‐averse producers, CT with usual fertilizer practice was more efficient than all other management options for the whole rotation. Farmers' risk aversion has no impact on the choice of the most efficient tillage and fertilizer management for potato (CT with usual fertilizer practice) and for corn (reduced tillage with increased fertilizer level). For wheat, the results show a high impact of risk aversion on the optimal choice of the tillage and fertilizer system. With increased energy prices, the economic savings of the reduced tillage systems due to reduced fuel use may be offset by higher fertilizer requirements since nitrous fertilizer prices are highly determined by energy costs.

Macronutrient concentration in plant parts of cotton fertilized with broiler litter in a marginal upland soil

Effectiveness of surface-applied unincorporated broiler litter as a fertilizer relative to conventional inorganic fertilizers under no-till or conventional-till cotton ( Gossypium hirsutum L.) production systems in the upland soils of the southern and southeastern USA is not well documented. The objectives of this research were to (1) test if broiler litter improves plant macronutrient (N, P, K, and Mg) nutrition of cotton above that of cotton fertilized with conventional inorganic fertilizers and (2) determine if lack of incorporating litter into the soil reduces macronutrient concentration in cotton plant parts in an upland soil considered marginal for cotton. Six treatments consisting of an unfertilized control, a fertilized standard (STD), two litter-only, and two litter plus inorganic N as urea–ammonium nitrate solution (UAN) were tested in two adjacent fields, one under no-till (NT) and the other under conventional-till (CT) systems. Litter alone, UAN, or a combination of litter plus UAN were applied to supply 101 kg ha −1 plant available N assuming nearly all of the UAN-N and 50% of the total litter N becomes plant available during the cotton growing season. Concentration of N, P, K, and Mg were measured in leaves, stems, and reproductive parts on three or four dates between early flowering and maturity. Cotton fertilized with the litter-only treatments always had less N concentration but greater P and K concentration in leaves, stems, and reproductive parts than cotton that received the STD treatment. Leaf and stem Mg concentration seems to depend on the N concentration in these plant parts. Lack of incorporating litter into the soil reduced N concentration in nearly all plant parts at all growth stages, suggesting some amount of the litter-derived N is lost due to lack of incorporation. Lack of incorporation also reduced leaf and stem Mg concentration, which seemed to be due to its reducing effect on N concentration. Unlike N and Mg, lack of incorporation did not consistently affect concentrations of P and K in all plant parts. Regardless of the incorporation treatment, fertilization with the litter-only treatments increased tissue P and K concentration and supported lint yield exceeding that of the STD without increasing tissue N concentration.

Corn Residue and Nitrogen Source Effects on Nitrogen Availability in No‐Till Corn

Effective N management practices are needed in high residue corn (Zea mays L.) production systems to enhance N fertilizer efficiency and avoid yield reductions due to inadequate N supplies. This 4‐yr study was conducted on a well‐drained silt loam soil in southern Wisconsin (43°17′ N, 89°22′ E) to determine the effects of corn residue cover amounts on soil and residue N supplying capability, the effectiveness of several surface‐applied N fertilizers, and the relative importance of mechanisms potentially contributing to reduced N efficiency in no‐till corn systems. Treatments consisted of corn residue level [none (0×), normal (1×), twice normal (2×), and artificial (polypropylene) residue (AR1×)], N fertilizer source (ammonium nitrate, urea, and urea–ammonium nitrate solution), and N rate (0–225 kg N ha−1 in 45‐kg increments). Increasing residue levels lowered soil temperatures and early season soil NO3–N production, and reduced corn grain yields without applied N. Ammonia losses reduced the effectiveness of urea‐containing fertilizers but did not completely explain the observed N source differences. Nitrogen source effects were similar at all residue levels, suggesting that added N can overcome yield reductions at high residue levels. Yields, N mineralization, and soil temperature were similar in the 1× and AR1× residue treatments, indicating that soil temperature rather than N immobilization is the main contributor to decreased yields at higher residue levels. Differences in early season soil NO3–N production and a similar difference in mean corn N requirement at the 0× and 1× residue levels, suggest that applying about 30 kg ha−1 of extra N will provide yield benefits in some years in no‐till corn residue systems.

Rate and mode of application of the urease inhibitor N‐(n‐butyl) thiophosphoric triamide on ammonia volatilization from surface‐applied urea

AbstractA laboratory study evaluated the effect of rate (0, 100, 250, 500, 750 or 1000 mg/kg) and mode of application of the urease inhibitor N‐(n‐butyl) thiophosphoric triamide (nBTPT) (coating the urea granule, adding to the urea melt or adding to urea ammonium nitrate (UAN) solutions) on NH3 volatilization from urea, at three temperatures (5, 15 and 25 °C), with four contrasting soil types. Daily ammonia loss was measured for up to 21 days after surface N application, using ventilated soil enclosures. Ammonia loss from unamended urea varied with soil type and temperature and ranged from 8.2 to 31.9% of the N applied. nBTPT was highly effective in lowering NH3 volatilization from urea and in delaying the time of maximum rate of loss. The average % inhibition over all soils, temperatures and formulations was 61.2, 69.9, 74.2, 79.2 and 79.8% for the 100, 250, 500, 750 or 1000 mg/kg nBTPT concentration, respectively. The % inhibition with nBTPT was lower at 15 °C compared with at 5 or 25 °C and was lower in UAN solutions than in granular products. There was little difference between the melted and coated granular products in lowering NH3 loss or in soil N transformations. The stability of nBTPT in urea products was dependent on its mode of application and on the storage temperature. Incorporating nBTPT in the urea melt produced a more homogeneous product with superior stability than coating the urea granule.

No‐Till and Conventional‐Till Cotton Response to Broiler Litter Fertilization in an Upland Soil: Lint Yield

The effectiveness of poultry litter as cotton (Gossypium hirsutum L.) fertilizer is not well documented for upland soils in the southern and southeastern United States. The objective of this research was to measure cotton yield response to broiler litter fertilization in contrast to inorganic N fertilization and to quantify yield reduction due to lack of incorporation under no‐till and conventional‐till systems in an upland soil. Six treatments were tested in two unreplicated adjacent fields, one under no‐till (NT) and the other under conventional‐till (CT) management, from 2003 to 2006 near Pontotoc, MS. The treatments consisted of an unfertilized control (UTC), a standard fertilization (STD) with urea‐ammonium nitrate solution (UAN), fertilization with ∼5.2 Mg ha−1 incorporated or unincorporated broiler litter to supply 67% of the N need plus 34 kg ha−1 UAN‐N to supply 33% of the N need, and fertilization with ∼7.8 Mg ha−1 incorporated or unincorporated broiler litter. Lint yield results showed broiler litter was a more effective cotton fertilizer than inorganic fertilizers under both NT and CT systems. The UTC produced an average across years of 870 kg ha−1 lint under NT and 1105 kg ha−1 under CT. The STD treatment increased yield over the UTC by only 121 kg ha−1 (14%) under the NT and did not affect yield under the CT. Fertilization with litter‐only when incorporated, relative to the UTC, increased lint yield by 260 kg ha−1 (30%) under NT and by 137 kg ha−1 (12%) under CT. The yield of this incorporated litter‐only treatment exceeded the yield of the STD treatment by 139 kg ha−1 (14%) under NT and by 115 kg ha−1 (10%) under CT. Fertilization with litter also resulted in greater leaf area index but less chlorophyll index than the STD treatment. Lack of litter incorporation reduced yield by up to 84 kg ha−1 under NT but did not affect yield under CT. Overall, broiler litter appears to be a more effective cotton fertilizer than conventional inorganic N fertilizers for this upland soil, but the inherent inability to incorporate under no‐till may reduce this benefit.

Biological Value of Red Beets in Relation to Nitrogen Fertilization

Biological Value of Red Beets in Relation to Nitrogen Fertilization Effects of nitrogen fertilizer and fertilization method on biological value of red beet roots (cv. Boro F1) were studied in pot experiments conducted in 2005 and 2006 years. Pre-sowing nitrogen fertilizers were either UAN (urea-ammonium nitrate solution) or ENTEC 26 (nitrogen fertilizer containing nitrification inhibitor). For both fertilizers the following methods of application were studied: pre-sowing superficially 90 kg N·ha-1 (S-100%), pre-sowing superficially 67.5 kg N·ha-1 with additional foliar nitrogen application during vegetation (S-75%+F), pre-sowing localized 67.5 kg N·ha-1 (L-75%) and pre-sowing localized 67.5 kg N·ha-1 with additional foliar nitrogen application during vegetation (L-75%+F). In harvested roots the contents of dry matter, sugars, phenols, NO3 -, NH4 +, N-protein and P, K, Mg and Ca were determined. Type of nitrogen fertilizer had no effect on dry matter, NH4 +, N-protein, sugars, phenols, Ca and Mg contents in both years and on K in 2005 year. ENTEC 26 reduced nitrates content, particularly in 2005 year. The effect of fertilization method was not univocal, particularly for NO3 - content. In 2005 the lowest NO3 - content was found in treatment S-100% roots, whereas in 2006 in L-75%. In both years the highest sugars content was observed in L-75% roots, and the lowest N-protein in S-100% roots. In both years the method of fertilization had no effect on dry matter, NH4 + and phenols contents. The effect of fertilization method of on mineral composition was apparent only in 2006 year. It can be concluded that by using the fertilizer with inhibitor of nitrification the biological value of red beets assessed by nitrate content can be improved. The effect of method of fertilizer application on the biological value of red beets is not univocal and may depend on the year of cultivation.

Phosphorus Extraction by Cotton Fertilized with Broiler Litter

Knowledge of the magnitude of P extracted and removed by harvested crop is an important component of effectively managing poultry litter to minimize or prevent the buildup of P in soil. This knowledge does not exist or is not well documented in cotton fertilized with litter as the primary fertilizer. The objective of this research was to quantify the magnitude of P extracted by cotton when fertilized with broiler litter and to determine whether supplementing litter with inorganic N improves P extraction. The research was conducted from 2002 to 2004 on two commercial farms representing a conventional‐till at Cruger and a no‐till at Coffeeville, MS, USA. At each location, the treatments consisted of an unfertilized control; a farm standard (STD) fertilized with inorganic fertilizers; and broiler litter of 2.2, 4.5, and 6.7 Mg ha−1 in an incomplete factorial combination with 0, 34, or 67 kg ha−1 N as urea ammonium nitrate (UAN) solution. The unfertilized control extracted an average across years of 27.7 kg P ha−1 at Cruger and 26.0 kg P ha−1 at Coffeeville. Application of both litter and UAN‐N decreased tissue P concentration but increased extracted amount of P because of increases in dry weight. The largest end‐of‐season P extraction in this research, which included 53.9 kg P ha−1 in 2004 at Cruger and 49.3 kg P ha−1 in 2002 at Coffeeville, was recorded for the treatment that received the largest litter rate of 6.7 Mg ha−1 supplemented with 34 or 67 kg ha−1 UAN‐N. Applied P always exceeded extracted P in all 3 yr at both locations when the litter rate was 4.5 or 6.7 Mg ha−1. Extracted P equaled or exceeded applied P when 2.2 Mg ha−1 litter was applied. Increasing litter rate decreased phosphorus extraction efficiency (PEE) while supplemental UAN‐N increased PEE. An average of 53% of the total P extracted was partitioned to seed with an additional 2.4% partitioned to lint for a total of 55% that would be removed with harvested crop. Nitrogen fertilization appeared to shift P partitioning from vegetative to reproductive parts. Supplementing litter with inorganic N may be an effective strategy not only in extracting additional P from soils but also in increasing the fraction partitioned to seed so that more P is removed from the field.

Lint Yield and Fiber Quality of Cotton Fertilized with Broiler Litter

Poultry litter is generated in large quantities in the same southeastern U.S. states where cotton (Gossypium hirsutum L.) is a dominant field crop, but is rarely used as a primary cotton fertilizer partly because of lack of adequate management recommendations. This research was conducted to determine adequate rates of broiler litter and whether supplementation with inorganic N would be necessary for optimum cotton lint yield and fiber quality. The research was conducted from 2002 to 2004 on two commercial farms representing conventional‐till (CT) and no‐till (NT) systems. The treatments consisted of an unfertilized control, a farm standard (STD) fertilized with inorganic fertilizers, and broiler litter of 2.2, 4.5, and 6.7 Mg ha−1 in an incomplete factorial combination with 0, 34, or 67 kg ha−1 N as urea–ammonium nitrate solution (UAN). Litter without supplemental UAN–N increased yield by 23 to 110 kg lint ha−1 for every 1.0 Mg ha−1 litter under both CT and NT. The often‐recommended litter rate of 4.5 Mg ha−1 was not adequate to increase yield to be equivalent to that of the STD that received 101 to 135 kg ha−1 as UAN. It was necessary to supplement this or the other litter rates with 34 or 67 kg ha−1. UAN–N to support yield equal to or greater than the yield of the STD. The most consistently well‐performing treatment under both tillage systems in all years was the 4.5 Mg ha−1 litter supplemented with 67 kg ha−1. UAN–N. Lint yield was highly correlated (r2 = 0.83–0.97) with applied total plant‐available N (NTPA) under both systems. Fiber quality, fiber length and micronaire in particular, also responded to NTPA, but the responses were smaller than lint yield. Litter when adequately supplemented with UAN–N did not adversely affect fiber quality. These results show broiler litter as much as 4.5 Mg ha−1 should be supplemented with inorganic N fertilizers when used as a primary cotton fertilizer and when the expected yield is ≈1700 kg ha−1 under CT and ≈1500 kg ha−1 under NT.

In-crop application effect of nitrogen fertilizer on grain protein concentration of spring wheat in the Canadian prairies

Due to the price premium for high-protein wheat (Triticum aestivum L.), many producers are interested in the efficacy of in-crop application of low rates of N fertilizer for increasing grain protein concentration (GPC). We conducted field studies at 26 site-years in Alberta, Saskatchewan and Manitoba from 1998 to 2000 to determine if in-crop application (tillering, boot stage or anthesis) of N fertilizer [broadcast ammonium nitrate (AN) or foliar urea-ammonium-nitrate solution (UAN); 15 kg N ha-1] could economically increase GPC of a Canada Western Red Spring (CWRS) wheat cultivar (AC Barrie). Basal N fertilizer rates were 60 and 120 kg N ha-1. The average increase in GPC due to in-crop N application was 3 g kg-1. The increase in GPC was similar at basal N rates of 60 and 120 kg N ha-1. Broadcast AN and foliar-applied UAN were generally equally effective at increasing GPC, but were not more effective than application at the time of seeding. Late application tended to increase GPC more effectively than early application. The increase in GPC due to application of in-crop N was not economic at most sites in this study, but might be greater if applied under more N deficient conditions. Key words: Split N application, foliar, timing

Imazamox Rates, Timings, and Adjuvants Affect Imidazolinone-Tolerant Winter Wheat Cultivars

Irrigated field experiments were conducted near Torrington, WY, during the 2001 to 2002 (year 1) and 2002 to 2003 (year 2) winter wheat growing seasons to evaluate cultivar response to different imazamox rates, adjuvants, and application timings. Five cultivars were treated postemergence in the early fall (EF), late fall (LF), or early spring (ES) with imazamox at 54 or 108 g ai/ha, including either nonionic surfactant (NIS) at 0.25% or methylated seed oil (MSO) at 1% (v/v) as adjuvants. A 28% urea ammonium nitrate solution at 1% (v/v) was included with all treatments. Spring injury was more severe in year 1 than year 2. Severe spring injury on ‘AP502 CL’, ‘Above’, ‘IMI-Fidel’, ‘IMI-Jagger’, and ‘IMI-Madsen’ was linked to fall application of 108 g/ha imazamox with MSO. Imazamox applied at 108 g/ha plus MSO applied in the fall consistently injured all cultivars more than the same rate with NIS and 54 g/ha imazamox regardless of adjuvant and timing, although severity of injury in the experiments differed between EF and LF timings in years 1 and 2, respectively. Correlation analysis supports injury reduced reproductive tillers per meter of row and wheat yields and increased the number of seeds per spike in year 1. The reduction of reproductive tillers per meter of row in year 1 was likely the result of severe injury caused by 108 g/ha imazamox applied in the EF coupled with little snow cover to protect against cold winter temperatures. Wheat yield in year 1 was reduced by 108 g/ha imazamox applied in the early fall; however, imazamox applied at 54 g/ha with either adjuvant in EF, LF, or ES were safe. Yield parameters and wheat yields in year 2 were not affected by imazamox rate, adjuvant, timing, or interactions of these factors.

Tillage and Urea Ammonium Nitrate Fertilizer Rate and Placement Affects Winter Wheat following Grain Sorghum and Soybean

In the eastern Great Plains, winter wheat (Triticum aestivum L.) is often rotated with other crops to diversify cropping systems. In these multicropping systems, wheat typically is planted with conservation tillage methods, but previous crop residues influence fertilizer N management. This field study was conducted from 1992 through 2001 in southeastern Kansas on a Parsons silt loam soil (fine, mixed, thermic, Mollic Albaqualf). The objectives were to determine effects and interactions of previous crop {grain sorghum [Sorghum bicolor (L.) Moench] and soybean [Glycine max (L.) Merr.]}, tillage system [reduced tillage (RT) and no‐tillage (NT)], N rate (67 and 134 kg ha−1), and preplant placement (surface‐broadcast and subsurface‐knife) of urea ammonium nitrate solution (UAN, 280 g kg−1) on wheat grain yield, yield components, and plant N uptake in a 2‐yr cropping rotation. Wheat yields averaged 3.39 Mg ha−1 following soybean compared with 2.90 Mg ha−1 following grain sorghum. Tillage effects on grain yield were smaller than other treatment factors, averaging 3.23 Mg ha−1 for RT and 3.06 Mg ha−1 for NT. Grain yields were greatest in all cropping systems for the high‐N‐rate subsurface‐knife treatment. Plant N uptake responses indicated that grain yield differences were primarily related to greater immobilization of both fertilizer and soil N following grain sorghum, compared with soybean, and to better utilization of subsurface‐knifed N than surface‐broadcast N. Results indicate that wheat yield potential is more strongly influenced by previous crop, fertilizer N rate, and N placement method than tillage system.

Effects of liquid swine manure applications on NO3–N leaching losses to subsurface drainage water from loamy soils in Iowa

Long-term applications of organic or inorganic sources of N to croplands can increase the leaching potential of nitrate– nitrogen (NO3–N) for soils underlain by subsurface drainage ‘‘tile’’ network. A field study was conducted for 6 years (1993– 1998) to determine the effects of liquid swine manure and urea ammonium nitrate (UAN) solution fertilizer applications on NO3–N concentrations and NO3–N losses with subsurface drainage water under continuous corn (Zea maize L.) and corn after soybean (Glycine max. L.) production systems. The field data collected at Iowa State University’s northeastern research center near Nashua, Iowa, under six N-management treatments and each replicated three times, were analyzed as a randomized complete block design. The flow weighted average (FWA) NO3–N concentrations in tile flow were affected significantly (P < 0.05) by N-application rates from swine manure, growing season and treatment effects. Peak (FWA) NO3–N concentrations values of 31.8 mg L 1 under swine manure and 15.5 mg L 1 under UAN in subsurface drain water were observed in 1995 following the dry year of 1994. The 6-year average crop rotation effects on NO3–N losses with tile flows were not found to be significantly affected either with swine manure or UAN-fertilizer applications but showed significant increase in corn grain yields under both the systems. Liquid swine manure, averaged across the 6-year period, resulted in significantly (P < 0.05) greater NO3–N losses with tile flows by 53% (26 kg N ha 1 versus 17 kg N ha 1 ) and showed no difference in corn grain yields in comparison with UAN-fertilizer applications under continuous corn production system. These results emphasize the need for better management of swine manure application system during the wet and dry growing seasons to reduce NO3–N leaching losses to shallow groundwater systems to avoid contamination of drinking water supplies. # 2005 Published by Elsevier B.V.

Response of Dry Bean and Weeds to Fomesafen and Fomesafen Tank Mixtures1

Field experiments were conducted in 2002 and 2003 to evaluate weed control and dry bean response to fomesafen and fomesafen tank mixtures. In the first experiment, six market classes of dry bean were treated at the first trifoliate growth stage with fomesafen nonionic surfactant (NIS) urea ammonium nitrate solution (UAN) at rates ranging from 210 to 840 g/ha. In the second experiment, fomesafen NIS UAN at 280 g/ha was applied alone or combined with imazamox at 36 g/ha, bentazon at 560 g/ha, or clethodim at 140 g/ha, and each treatment was applied postemergence at either the unifoliate, first trifoliate, or third trifoliate growth stage to six dry bean cultivars. Crop injury from fomesafen in the form of stunting and leaf crinkling was apparent 7 d after treatment (DAT), but crop injury was temporary and plants recovered. Common lambsquarters and hairy nightshade control increased from 61 to 71% and 74 to 92%, respectively, as fomesafen rate increased from 210 to 280 g/ha. Redroot pigweed, kochia, and common purslane were controlled at the ≥90% level by fomesafen at 210 g/ha. Applying fomesafen and fomesafen tank mixtures at the unifoliate growth stage caused less dry bean injury and improved redroot pigweed, common lambsquarters, and hairy nightshade control compared with treatments made at the first or third trifoliate growth stage. Decreased weed control caused by delaying herbicide application to the third trifoliate growth stage resulted in a 17% decrease in crop yield, compared with treatments where herbicides were applied at the unifoliate growth stage. Combining fomesafen with other herbicides increased crop injury 4%, 14 DAT. A tank mixture of fomesafen plus imazamox caused more crop injury than fomesafen plus bentazon. Combining fomesafen with imazamox or bentazon improved hairy nightshade control to 92 and 87%, respectively; however, common lambsquarters control was improved only with tank mixtures of fomesafen with bentazon.Nomenclature: Bentazon; clethodim; fomesafen; imazamox; common lambsquarters, Chenopodium album L. #3 CHEAL; common purslane, Portulaca oleracea L. # POROL; hairy nightshade, Solanum sarrachoides Sendt. # SOLSA; kochia, Kochia scoparia (L.) SCHRAD. # KCHSC; redroot pigweed, Amaranthus retroflexus L. # AMARE; dry bean, Phaseolus vulgaris L. black, Great Northern, light red kidney, navy, pink, pinto, ‘Shadow’, ‘Marquis’, ‘Chinook’, ‘Schooner’, ‘Viva’, ‘Poncho’.Additional index words: Field beans, interference, seed yield.Abbreviations: DAT, days after treatment; NIS, nonionic surfactant; POST, postemergence; UAN, urea ammonium nitrate solution.

Foliar Burn and Wheat Grain Yield Responses Following Topdress-Applied Nitrogen and Sulfur Fertilizers

The most common fertilizer sources for topdress nitrogen (N) applications to winter wheat (Triticum aestivum L.) in Virginia are a urea ammonium nitrate (UAN) solution (30-0-0) or a UAN solution with added sulfur (S) (UAN-S; 20-0-0-4). However, there are some concerns regarding leaf burning following foliar N applications, particularly at later growth stages. An experiment was conducted from 1999 through 2002 to evaluate and quantify foliar burn associated with various topdress-applied N sources, any subsequent effect on wheat grain yield, and any yield response to added S. Ammonium nitrate (AN; 34-0-0), UAN, UAN-S, and ammonium sulfate (AS; 21-0-0-24) were topdress-applied at either GS 30 or 32. Following the GS 30 and 32 foliar applications, digital images were obtained from each plot and pixel analysis was used to estimate the percentage of foliar burn. At GS 30, foliar burn increased with increasing N rate with no difference in the percentage of burn being observed between sources. At GS 32, foliar burn again increased with increasing N rate; however, UAN-S resulted in significantly greater foliar burn than UAN at both N rates. Despite the increased foliar damage that occurred when UAN-S was topdress-applied at GS 32, there was no reduction in grain yield compared with UAN or either of the soil-applied sources at either growth stage. Although there was no evidence of a grain yield response to added S in this study, many soil types common to the Coastal Plain of Virginia are likely to lack sufficient S for optimum winter wheat production.

Cotton Response to Source and Timing of Nitrogen Fertilization on a Sandy Coastal Plain Soil

A three‐year field study was conducted to evaluate cotton (Gossypium hirsutum L.) response to the source and timing of nitrogen (N) on an irrigated coastal plain soil (Lucy loamy sand; Arenic Kandiudults) in south Alabama. Cotton acreage in this region has increased in the past ten years and there was a need for current data describing cotton response to N fertilization. Treatments included N sources, timing of N application (ammonium nitrate), split applications of N (ammonium nitrate and ammonium sulfate), and a no‐N check. Nitrogen sources applied preplant included: (i) ammonium nitrate (34‐0‐0); (ii) ammonium sulfate (21‐0‐0‐24.2); (iii) urea (46‐0‐0); (iv) urea–ammonium nitrate solution (UAN; 32‐0‐0); (v) UAN + ammonium thiosulfate (28‐0‐0‐5). Non‐sulfur sources were applied with and without additional sulfur (S). Times of application were preplant, first true leaf, first square, and first bloom. Two treatments received split applications of N as a 50:50 mixture of ammonium sulfate with urea or ammonium nitrate. Supplemental applications of potassium (K) were evaluated by applying ammonium sulfate in combination with 56 kg K/ha. Yield data showed some minor differences among sources, but overall the results of this three‐year study show that there were no superior N sources. For ammonium nitrate, preplant applications of N were sufficient in two out of three years. Split applications of ammonium nitrate did not improve yields as compared to preplant N. Applying ammonium sulfate with supplemental K or as a 50:50 mixture with ammonium nitrate or urea did not improve yields as compared to ammonium sulfate or ammonium nitrate applied alone. Lint quality was not affected by N fertility treatments.

NEITHER BLOOM PERIOD NOR POSTBLOOM NITROGEN APPLICATION REDUCES COLD HARDINESS IN CRAPEMYRTLE

In a 2-year field study, 5-year-old field-grown ‘Natchez’ crapemyrtles were either not fertilized with nitrogen (N), or received 100 kg N/ha (89 lbs N/acre) as urea-ammonium nitrate solution applied in six biweekly applications either mid-June through early August (bloom stage) or late August through late October (post bloom). Treatments had virtually no effect on the development or degree of cold hardiness attained as measured by lowest survival temperature on twig samples collected monthly from November to March. Nitrogen application increased leaf N concentration in 1994, but not in 1995. Nitrogen fertilization reduced leaf phosphorus (P) concentrations both years, presumably due to the dilution effect, but only reduced the leaf potassium (K) concentration in August 1994. Nitrogen treatments increased stem diameter 4% compared to the control, but sidedress timing had no effect.

Corrosion Characteristics of Mild Steel in Urea Ammonium Nitrate Fertilizer Solutions

Abstract Anodic polarization studies have been conducted on mild steel in urea ammonium nitrate (UAN) fertilizer solutions comprising 31 wt% urea ([NH2]2CO), 39 wt% ammonium nitrate (NH4NO3), and 30 wt% H2O, with a total N content of 28 wt% (UAN 28-0-0). It was determined that mild steel can spontaneously exhibit either active-passive or passive behavior when immersed in UAN solutions. At 23°C, specimens exhibiting active-passive behavior experienced corrosion rates of ∼2 mm/y for pH values in the range of 3 to 8.5. At pH values <3, the corrosion rate increased rapidly, reaching a value of 92 mm/y at a pH of 1.1. Specimens exhibiting passive behavior experienced corrosion rates of ∼0.002 mm/y for the pH range of 6 to 8.5. An increase in temperature from 23°C to 60°C increased the corrosion rate of specimens exhibiting active-passive behavior from ∼2 mm/y to ∼15 mm/y. To minimize corrosion, mild steel storage tanks for liquid UAN fertilizer should be kept free of sludges and other contaminants, which could...

Weed Control in Dry Pea (Pisum sativum) Under Conventional and No-Tillage Systems1

Herbicides were evaluated for weed control and crop response in conventional and no-tillage dry pea production. Preplant or preemergence (PRE) applications of imazethapyr, sulfentrazone, flumetsulam, cloransulam, and BAY FOE 5043 metribuzin did not show crop injury within the locations, years, and tillage systems where applied. Postemergence applications of cloransulam had crop injury in excess of 60% where applied, and injury with flumiclorac and fomesafen ranged from 0 to greater than 40% with differences in crop injury as a result of dry pea growth stage at the time of application and surfactant use. Imazamox injury was as great as 24% when applied at a more advanced dry pea growth stage and was not different from 0% when applied at an earlier growth stage. Dry pea injury with bentazon was not significant, with an exception at one of the six locations where injury was 14%. Common lambsquarters was best controlled (80 to 90%) with sulfentrazone and imazamox. Preplant and PRE applications of sulfentrazone consistently provided the greatest mayweed chamomile control across tillage systems (control ranged from 59 to 93%), whereas bentazon provided the greatest postemergence (POST) control of mayweed chamomile (control ranged from 46 to 84%). Prickly lettuce control with preplant or PRE treatments was greatest with sulfentrazone (74 to 85%), whereas the greatest POST control was with imazamox in combination with urea-ammonium nitrate solution and surfactant or bentazon and crop oil concentrate (71 to 92%). Dry pea yields with herbicide treatments were not always greater than the nontreated and were often affected by crop injury.Nomenclature: BAY FOE 5043, N-(4fluorophenyl)-N-(1-methylethyl)-2-[[5-(trifluoromethyl)-1,3,4-thiadiazol-2-yl]oxy]acetamide; bentazon; cloransulam; flumetsulam; flumiclorac; fomesafen; imazamox; imazethapyr; metribuzin; sulfentrazone; common lambsquarters, Chenopodium album L. #3 CHEAL; dry pea, Pisum sativum L., ‘Columbia’, ‘Phantom’; mayweed chamomile, Anthemis cotula L. # ANTCO; prickly lettuce, Lactuca serriola L. # LACSE.Additional index words: Conservation tillage, herbicide efficacy, pea yield.Abbreviations: COC, Crop Oil Concentrate; DAT, days after treatment; FPP, fall preplant; NIS, nonionic surfactant; POST, postemergence; PPI, preplant incorporated; PRE, preemergence; SPP, spring preplant; UAN, urea-ammonium nitrate solution.

CROPPING SYSTEM EFFECTS ON NO3–N LOSS WITH SUBSURFACE DRAINAGE WATER

An appropriate combination of tillage and nitrogen management practices will be necessary to develop sustainable farming practices. A six–year (1993–1998) field study was conducted on subsurface–drained Clyde–Kenyon–Floyd soils to quantify the impact of two tillage systems (chisel plow vs. no tillage) and two N fertilizer management practices (preplant single application vs. late–spring soil test based application) on nitrate–nitrogen (NO3–N) leaching loss with subsurface drain discharge from corn (Zea mays L.) soybean (Glycine max L.) rotation plots. Preplant injected urea ammonium nitrate solution (UAN) fertilizer was applied at the rate of 110 kg ha–1 to chisel plow and no–till corn plots, while the late–spring N application rate averaged 179 and 156 kg ha–1 for the no–till and chisel plow corn plots, respectively. Data on subsurface drainage flow volume, NO3–N concentrations in subsurface drainage water, NO3–N loss with subsurface drainage flow, and crop yield were collected and analyzed using a randomized complete block design. Differences in subsurface drainage flow volume due to annual variations in rainfall significantly (P = 0.05) affected the NO3–N loss with subsurface drainage flows. High correlation (R2 = 0.89) between annual subsurface drainage flow volume and the annual NO3–N leaching loss with subsurface drainage water was observed. The flow–weighted average annual NO3–N concentrations varied from a low of 6.8 mg L–1 in 1994 to a high of 13.9 mg L–1 in 1996. Results of this study indicated that NO3–N losses from the chisel plow plots were 16% (16 vs. 19 kg–N ha–1) lower in comparison with no–till plots, while corn grain yield was 11% higher in the chisel plow plots (8.3 vs. 7.5 Mg ha–1). Late–spring N application applied as a sidedress resulted in 25% lower NO3–N leaching losses with subsurface drainage water in comparison with preplant single N application and also significantly (P = 0.5) higher corn grain yield by 13% (8.4 vs. 7.4 Mg ha–1). These results clearly demonstrate that chisel plow tillage with late–spring soil test based N application for corn after soybean can be a sustainable farming practice for the northeast part of Iowa.

Application of the Life Cycle Assessment methodology to agricultural production: an example of sugar beet production with different forms of nitrogen fertilisers

The suitability of the Life Cycle Assessment (LCA) methodology to analyse the environmental impact of agricultural production is investigated. The first part of an LCA is an inventory of all the resources used and emissions released due to the system under investigation. In the following step, i.e. the Life Cycle Impact Assessment the inventory data were analysed and aggregated in order to finally get one index representing the total environmental burden. For the Life Cycle Impact Assessment (LCIA) the Eco-indicator 95 method has been chosen, because this is a well-documented and regularly applied impact assessment method. The resulting index is called Eco-indicator value. The higher the Eco-indicator value the stronger is the total environmental impact of an analysed system. A sugar beet field experiment conducted in northeastern Germany was chosen as an example for the analysis. In this experiment three different nitrogen fertilisers (calcium ammonium nitrate=CAN, urea ammonium nitrate solution=UAN, urea) were used at optimum N rates. The obtained Eco-indicator values were clearly different for the N fertilisers used in the sugar beet trial. The highest value was observed for the system where urea was used as N source. The lowest Eco-indicator value has been calculated for the CAN system. The differences are mainly due to different ammonia volatilisation after application of the N fertilisers. For all the systems the environmental effects of acidification and eutrophication contributed most to the total Eco-indicator value. The results show that the LCA methodology is basically suitable to assess the environmental impact associated with agricultural production. A comparative analysis of the system, contribution to global warming, acidification, eutrophication and summer smog is possible. However, some important environmental issues are missing in the Eco-indicator 95 method (e.g. the use of resources and land).