Use Of Nitrification Inhibitors Research Articles

Nitrous Oxide Emissions from New Zealand Agriculture – key Sources and Mitigation Strategies

In most countries, nitrous oxide (N2O) emissions typically contribute less than 10% of the CO2 equivalent greenhouse gas (GHG) emissions. In New Zealand, however, this gas contributes 17% of the nation’s total GHG emissions due to the dominance of the agricultural sector. New Zealand’s target under the Kyoto Protocol is to reduce GHG emissions to 1990 levels. Currently total GHG emissions are 17% above 1990 levels. The single largest source of N2O emission in New Zealand is animal excreta deposited during grazing (80% of agricultural N2O emissions), while N fertilizer use currently contributes only 14% of agricultural emissions. Nitrogen fertilizer use has, however, increased 4-fold since 1990. Mitigation strategies for reducing N2O emissions in New Zealand focus on (i) reducing the amount of N excreted to pasture, e.g. through diet manipulation; (ii) increasing the N use efficiency of excreta or fertilizer, e.g. through grazing management or use of nitrification inhibitors; or (iii) avoiding soil conditions that favour denitrification e.g. improving drainage and reducing soil compaction. Current estimates suggest that, if fully implemented, these individual measures can reduce agricultural N2O emissions by 7–20%. The highest reduction potentials are obtained from measures that reduce the amount of excreta N, or increase the N use efficiency of excreta or fertilizer. However, New Zealand’s currently used N2O inventory methodology will require refinement to ensure that a reduction in N2O emissions achieved through implementation of any of these mitigation strategies can be fully accounted for. Furthermore, as many of these mitigation strategies also affect other greenhouse gas emissions or other environmental losses, it is crucial that both the economic and total environmental impacts of N2O mitigation strategies are evaluated at a farm system’s level.

Legume-based farming in Southern Australia: developing sustainable systems to meet environmental challenges

Development of legume-based farming systems has resulted in Australian agriculture being globally competitive. There is now political pressure for agriculture to become accountable for ‘off-site’ environmental consequences. Farming systems relying on annual species are unsustainable because of a mismatch between the supply and demand of water and N, resulting in N leakage to streams or groundwater. Rainfall in excess of plant requirements coupled with N build-up, permeable soils, limited opportunities for reduction and proximity to surface or groundwater present risks for leakage of NO 3–N. We present examples of N leakage from legume systems in southern Australia, where rainfall exceeds 450 mm yr −1, and the evidence suggesting that leakage contributes to stream and groundwater pollution. N build-up in autumn through mineralisation of organic-N from legume-based systems often exceeds 100 kg N ha −1 and N leakage losses can be 15–35 kg N ha −1 yr −1. Stream and groundwater N pollution issues are emerging. Surface water quality problems are already apparent in Victoria although the contribution from legumes, N fertilisers and point sources remains unresolved. Examples of groundwater problems where legumes are a contributing factor have been recorded in New South Wales (NSW), South Australia (SA), Western Australia (WA) and Victoria. In Victoria, areas at risk of N groundwater contamination are found along the Great Dividing Range and in southern Victoria. Groundwater pollution causes concern because once problems are found they take decades to reverse. Stores of N in the unsaturated zone combined with limited N monitoring in groundwater suggests that early detection is unlikely. Solutions for reducing off-site consequences are outlined and include management to prevent water and N leakage happening, capture of N before it reaches waterways or groundwater and low input systems including land retirement. For scientists interested in N fixation and biological mediation, future research areas include increasing the proportion of perennials in farming systems, better control of N supply and demand through improved technology and us of N fertiliser, use of nitrification inhibitors and studies of the potential for N immobilisation and reduction through denitrification, both within and below the root zone. Integrated management strategies that address environmental implications from point/micro-scale to paddock and catchment scales are needed as are considerations of other environmental consequences. Research priorities will change from maximising N fixation for profitability towards balancing profitability and environmental goals for more sustainable systems.

IMPLICATIONS OF ON‐GROUND NITROGEN LOADING AND SOIL TRANSFORMATIONS ON GROUND WATER QUALITY MANAGEMENT1

ABSTRACT: This paper presents a modeling approach based on a geographic information system (GIS) to estimate the variability of on‐ground nitrogen loading and the corresponding nitrate leaching to ground water. The methodology integrates all point and nonpoint sources of nitrogen, the national land cover database, soil nitrogen transformations, and the uncertainty of key soil and land use‐related parameters to predict the nitrate mass leaching to ground water. The analysis considered 21 different land use classes with information derived from nitrogen sources such as fertilizer and dairy manure applications, dairy lagoons, septic systems, and dry and wet depositions. Simulations were performed at a temporal resolution of one month to capture seasonal trends. The model was applied to a large aquifer of 376 square miles in Washington State that serves more than 100,000 residents with drinking water. The results showed that dairy manure is the main source of nitrogen in the area followed by fertilizers. It was also seen that nitrate leaching is controlled by the recharge rate, and there can be a substantial buildup of soil nitrogen over long periods of time. Uncertainty analysis showed that denitrification rate is the most influential parameter on nitrate leaching. The results showed that combining management alternatives is a successful strategy, especially with the use of nitrification inhibitors. Also, change in the land use pattern has a noticeable impact on nitrate leaching.

Approaches to Management Zone Definition for Use of Nitrification Inhibitors

Site-specific use of nitrification inhibitors has been proposed as one means of reducing the cost of nitrification inhibitor use on fields that vary in their potential for leaching or denitrification. This study evaluated one approach for site-specific use of the nitrification inhibitor nitrapyrin (2-chloro-6-[trichloromethyl] pyridine) based on slope and surface texture. Treatments of uniform and variable N fertilizer and nitrapyrin were applied to field length strips in a center-pivot irrigated field planted to maize (Zea mays L.) from 1995 to 1998. Nitrapyrin application was controlled spatially according to an arbitrary leaching potential derived from slope and surface soil texture. Growing seasons were grouped into dry, wet, or average precipitation years. Alternative approaches for nitrapyrin management zones based on fuzzy cluster analysis of grain yield or soil apparent electrical conductivity (EC,) were compared with the slope-texture management zone approach. There were small effects of nitrapyrin application method (none, uniform or variable) on grain yield. Uniform nitrapyrin application increased yield in a wet year. Fuzzy cluster analysis of grain yield or soil EC a identified unique patterns of yield or soil EC a . Yield clusters corresponded to patterns of water availability or excess. There were small effects of N or nitrapyrin application method on soil residual NO 3 -N. Yield Cluster 3 soils had higher residual NO 3 -N levels all 4 yr. In a wet year (1996) NO 3 -N levels were lowest in yield Cluster 2 soils-in the other 3 yr of the study, there was no difference in NO,-N levels between yield Clusters 1 and 2. Soil EC a clusters corresponded closely to soil series. There were significant correlations between soil EC a and yield clusters. Fuzzy cluster analysis has the potential to define management zones for use of nitrification inhibitors from relatively easily obtained spatial yield or soil EC a , rather than expensive grid sampling of soil chemical and physical properties.

Approaches to Management Zone Definition for Use of Nitrification Inhibitors

Site-specific use of nitrification inhibitors has been proposed as one means of reducing the cost of nitrification inhibitor use on fields that vary in their potential for leaching or denitrification. This study evaluated one approach for site-specific use of the nitrification inhibitor nitrapyrin (2-chloro-6-[trichloromethyl] pyridine) based on slope and surface texture. Treatments of uniform and variable N fertilizer and nitrapyrin were applied to field length strips in a center-pivot irrigated field planted to maize (Zea mays L.) from 1995 to 1998. Nitrapyrin application was controlled spatially according to an arbitrary leaching potential derived from slope and surface soil texture. Growing seasons were grouped into dry, wet, or average precipitation years. Alternative approaches for nitrapyrin management zones based on fuzzy cluster analysis of grain yield or soil apparent electrical conductivity (ECa) were compared with the slope-texture management zone approach. There were small effects of nitrapyrin application method (none, uniform or variable) on grain yield. Uniform nitrapyrin application increased yield in a wet year. Fuzzy cluster analysis of grain yield or soil ECa identified unique patterns of yield or soil ECa Yield clusters corresponded to patterns of water availability or excess. There were small effects of N or nitrapyrin application method on soil residual NO3-N. Yield Cluster 3 soils had higher residual NO3-N levels all 4 yr. In a wet year (1996) NO3-N levels were lowest in yield Cluster 2 soils—in the other 3 yr of the study, there was no difference in NO3-N levels between yield Clusters 1 and 2. Soil ECa clusters corresponded closely to soil series. There were significant correlations between soil ECa and yield clusters. Fuzzy cluster analysis has the potential to define management zones for use of nitrification inhibitors from relatively easily obtained spatial yield or soil ECa, rather than expensive grid sampling of soil chemical and physical properties.

Adoption of nutrient management techniques to reduce hypoxia in the Gulf of Mexico

Data were collected from 1011 land owner-operators within three watersheds located in the North Central Region of the USA to examine use of selected water protection practices. A theoretical model developed from selected components of the traditional diffusion paradigm and the farm structure model was used to predict adoption and use of conservation practices at the farm level within the study watersheds. Study findings revealed that factors commonly purported to be highly correlated with adoption of conservation production systems were not useful for predicting use of conservation production practices assessed. The production practices examined in the study were percent of cultivated fields surrounded by grass filter strips, percent of waterways in cultivated fields protected by grass, use of banded fertilizer, use of side dressing of fertilizer, and use of nitrification inhibitor. Study findings revealed that the theoretical model developed to guide the study was relatively ineffective for predicting adoption of the conservation practices assessed in the study. None of the statistical models developed from analysis of study data explained more than nine percent of the variance in any of the conservation practices assessed. Research findings suggest that existing conservation programs are no longer useful policy instruments for motivating land owner-operators to adopt and use production systems designed to reduce agricultural pollution of waterways.

Nitrapyrin Behavior in Soils and Environmental Considerations

AbstractUsing nitrification inhibitors is a well‐established fertilizer best management practice affording improved fertilizer use efficiency in crop production that may benefit profitability, crop quality, and the environment. The environmental benefit of nitrification inhibitor use in terms of managing N mobility in agroecosystems must be balanced against any environmental costs associated with the practice itself. Nitrapyrin exhibits multiple routes of degradation in the environment (hydrolysis, aerobic and anaerobic metabolism), which along with sorption and volatilization restrict its ability to mobilize to ground or surface water. Management practices (timing, rate, and method of application) that maximize nitrapyrin efficacy, additionally, favor the ultimate fate of nitrapyrin to occur by the linked processes of sorption and degradation within the upper soil profile. Thus, when nitrapyrin is used as a best management practice conducive of optimal fertilizer use efficiency, its environmental fate and behavior attributes minimize potential environmental exposure.

Use of nitrification inhibitors (neem and DCD) to increase N efficiency in maize-wheat cropping system

A 2-year field experiment was conducted to study the effects of the nitrification inhibitors dicyandiamide (DCD) and neem cake on the efficiency of applied prilled urea nitrogen in a maize-wheat cropping system. Prilled urea (PU), neem cake coated urea (NCU) and DCD blended urea (DCDU) were applied to maize at two levels (60 and 120 Kg N ha−1) and two methods (all preplant and split) of N application along with a no-nitrogen control and their relative residual effect was studied on succeeding wheat grown with three levels of N as PU.

Effect of encapsulated calcium carbide and urea application methods on denitrification and N loss from flooded rice

Poor N fertilizer use efficiency by flooded rice is caused by gaseous losses of N. Improved fertilizer management and use of nitrification inhibitors may reduce N losses. A microplot study using15N-labelled urea was conducted to investigate the effects of fertilizer application method (urea broadcast, incorporated, deep-placed) and nitrification inhibitor [encapsulated calcium carbide (ECC)] treatments on emission of N2+N20 and total loss of applied N on a grey clay near Griffith, NSW, Australia. Both incorporation and deep placement of urea decreased N2+N2O emission compared to urea broadcast into the floodwater. Addition of ECC significantly (P < 0.05) reduced emission of N2+N20 from incorporated or deep-placed urea and resulted in increased exchangeable ammonium concentrations in the soil in both treatments. Fifty percent of the applied N was lost when urea was broadcast into the floodwater. Total N loss from the applied N was significantly (P < 0.05) reduced when urea was either incorporated or deep placed. In the presence of ECC the losses were reduced further and the lowest loss (34.2% of the applied N) was noted when urea was deep-placed with ECC.

Reducing denitrification loss with nitrification inhibitors following presowing applications of urea to a cottonfield

The effects of the nitrification inhibitors nitrapyrin, acetylene (provided by wax-coated calcium carbide), and phenylacetylene on nitrogen (N) transformations and denitrification losses following presowing applications of urea were determined in a cottonfield in the Namoi Valley of New South Wales. The study used 0.05-m-diameter microplots to follow the changes in mineral N, and 0.15-m-diameter microplots fertilised with 15N-labelled urea (6 g N/ m2; 5 atom % 15N) to assess losses of applied N. When urea was applied in February (34 weeks before sowing), 84% of applied N was lost from the soil. Loss of applied N was reduced by addition of nitrapyrin and phenylacetylene, to 53 and 57%, respectively. In the absence of nitrification inhibitors, less N was lost (72% of that applied) from an application in May than from the February application. Addition of acetylene, phenylacetylene, and nitrapyrin reduced losses over the 24 weeks to sowing to 57, 52, and 48%, respectively. These experiments show that N loss from presowing applications of urea can be significantly reduced by the use of nitrification inhibitors, but that the losses of N are still substantial.

Nitrification Inhibitor Influences on Potato

AbstractNitrification inhibitors may reduce loss of fertilizer N from the root zone by reducing leaching and denitrification. This reduced N loss should be reflected in increased crop yields. These studies were conducted to determine if potato yield, specific gravity, or leaf N at flowering would be increased by use of nitrification inhibitors. Nitrification inhibitors dicyandiamide (DCD) and 2‐chloro‐6‐(trichloromethyl)‐ pyridine (nitrapyrin) were evaluated in five studies on potato (Solanum tuberosum L. cv. Atlantic) in Northeast Florida on an Arenic Ochraqualf, a Grossarenic Paleudult, and a Grossarenic Paleaquult. Treatments were combinations of N at 67, 134, and 202 kg ha−1; DCD at 0, 5.6, and 11.2 kg ha−1; nitrapyrin at 0.56 and 1.12 kg ha−l; and isobutylidene diurea (IBDU) applied as one‐third of the N. Tuber yields were not affected by nitrification inhibitors in four of five tests but were increased 14% in one test. Nitrification inhibitors increased leaf N concentration at flowering in three of four tests. Tuber yields were higher with DCD than with nitrapyrin in three of five tests. In several year‐location combinations, use of IBDU resulted in greater tuber yield and leaf N concentration at flowering than did nitrification inhibitors. Based on these results, nitrification inhibitors can not be recommended for potato production on hyperthermic, sandy, irrigated soils.

Use of nitrification inhibitors to increase fertilizer nitrogen recovery and lint yield in irrigated cotton

This paper describes field experiments designed to evaluate the effectiveness of several nitrification inhibitors to prevent loss of fertilizer nitrogen (N) applied to cotton. The usefulness of nitrapyrin, acetylene (provided by wax-coated calcium carbide), phenylacetylene and 2-ethynylpyridine to prevent denitrification was evaluated by determining the recovery of N applied as15N labelled urea to a heavy clay soil in 1 m × 0.5 m microplots in north western N.S.W., Australia. In a second experiment, the effect of wax-coated calcium carbide on lint yield of cotton supplied with five N levels was determined on 12.5 m × 8 m plots at the same site.

Response of Corn to Preplant Applications of Nitrogen and to Nitrogen Plus Nitrapyrin

Several factors, including N rate, N source, timing of application, and use of nitrification inhibitors, can influence yield and N-use efficiency of corn (Zea mays L.). A field experiment was conducted for 7 yr to determine if the use of nitrapyrin [2-chloro-6-(trichloromethyl) pyridine] applied with preplant, broadcast N applications as urea or urea-NH4NO3 (UAN) solution could influence corn grain yield, grain moisture at harvest, ear weight, and other parameters. A zero N check and two rates of N with and without nytrapyrin were applied on the same plots each year for 6 yr. In the seventh year, a crop was planted on the test area without N application to evaluate residual effects due to various treatments. A consistent yield response was observed to N in all years, including the residual year. The use of nitrapyrin increased yields with both N rates with the greatest benefit occurring at the lower of the two N rates. Additionally, the yield produced with nitrapyrin and the low N rate were consistently equal to yields produced with the high N rate without nitrapyrin. Yield differences resulted from a combination of increased ears per plot and increased ear weight. Both increasing N rate and use of nitrapyrin resulted in lower grain moisture levels in some years. In the residual year, yields were higher where N had been applied previously. Higher yields occurred where nitrapyrin had been used, suggesting greater N carryover from product use.

Urea and Anhydrous Ammonia Management for Conventional Tillage Corn Production

Nitrogen management for conventional tillage (CT) corn (Zea mays L.) production is highly dependent on local soil and climatic conditions. Nitrogen fertilizer source, time of application, and use of nitrification inhibitors (NI) are components of an N management program which easily can be varied by the producer. An 8-yr study was undertaken in Ohio to assess N fertilizer management for CT corn production on a Crosby silt loam soil (fine, mixed, mesic Aerie Ochraqualf). Nitrogen fertilizer treatments compared in the study were fall and spring-preplant broadcast and incorporated urea, and fall and spring-preplant anhydrous ammonia (AA), with and without the NI, nitrapyrin [2-chloro-6-(trichloromethyl) pyridine]. Each N treatment was applied at rates of 80 and 160 lb/acre. Spring urea also was applied at 240 and 320 lb N/acre. Both grain yield and percent N in the ear leaf at tasseling were increased with increases in N rate for all N source × application time × NI treatments. For increasing rates of N, anhydrous ammonia produced higher yields and gave greater increases in percent ear-leaf N than did urea. Spring-preplant application of both N sources gave higher yields than fall application. Nitrapyrin with spring-applied AA gave no yield or percent ear-leaf N increases. However, NI with fall-applied AA did increase grain yield over fall-applied AA without NI. While significant year-to-year and treatment year variability was present in the study, the 8-yr average results can be used in formulating N management recommendations for CT corn production in similar soils in the North Central USA.

Agronomic and public aspects of soil nitrogen research

Abstract. Public perceptions of agriculture as a contributor to environmental stress are resulting in changes within agricultural production systems. Increasingly, these systems will need to be economically viable, environmentally sound, socially and politically acceptable, and conserving of natural resources‐the characteristics that describe a sustainable agriculture. Improving and maintaining agricultural production systems with these characteristics must continue to be the objectives of agricultural research. Nitrogen research has contributed markedly to meeting the production and economic goals of agriculture, but it has not yet focused enough on answering socially and politically sensitive questions. Questions are posed about the environmental effects of various nitrogen management practices and the research needed to answer them is outlined. Emphasis is put on immobilization‐mineralization as affected by use of nitrification inhibitors and split‐application, release of nitrogen from animal manures, legumes, and other crop residues, and establishing acceptable yield goals.

Use of Nitrification Inhibitors with Summer Applications of Swine Manure

A two-year study was conducted to determine the effects of inhibiting nitrification on the fertilizer value of swine manure applied in the summer season. Nitrapyrin (0.56, 1.12, 1.68 kg/ha; 0.5, 1.0, 1.5 lbs/ac) or etradiazol (1.2 kg/ha; 1.0 lb/ac) was added to swine manure from a finishing house. All manures were injected at the rate of 22 450 to 35 078 L/ha (2400 to 3750 gal/ac) into an Odell silt loam soil following wheat (Triticum aestivum) harvested in early July. Total nitrogen application rates on the manure plots ranged from 168 to 224 kg N/ha (150 to 200 lbs N/ac) based on the corn plant requirement of 207 kg N/ha (185 lb N/ac) with a 9415 kg/ha (150 bu/ac) grain yield. At above optimal nitrogen application levels, average corn yields were increased 5% by the addition of a nitrification inhibitor. The beneficial effects of nitrification inhibitors on corn yields were greater (13.5%) when manure was applied at the 168 kg N/ha (150 lb N/ac) rate as compared to the 224 kg N/ha (200 lb N/ac) rate. Response to the higher rate of nitrogen indicated excess N was applied than needed for grain production, which compensated partially for N loss. Over the entire study, adding 1.12 kg/ha (1.0 lb/ac) of nitrapyrin to manure increased corn yields the most compared to other inhibitor levels or etradiazol. Soil nutrient levels did not increase from the manure applications. There was a lower incidence of stalk rot when nitrification was inhibited.

Effect of nitrogen rate, nitrogen timing, and nitrification inhibitors on grain sorghum production in Arkansas

Abstract Nitrogen efficiency may be improved in grain sorghum [Sorghum bicolor (L.) Moench.] production by using the optimum N rate, splitting the N applications, and by the use of nitrification inhibitors. Nitrogen rates of 0, 56, 112, 168, and 224 kg N/ha with and without nitrification inhibitors, dicyandiamide (DCD) and nitrapyrin, were evaluated in 1985 and 1986 at two locations in Arkansas. Selected N rates were evaluated when applied all preplant and when the applications were split. In 1986, at one location, two N rates (0 and 168 kg N/ha), DCD and nitrapyrin, and different times of N application were evaluated. These treatments were evaluated at two soil water deficits, 2 and 4 cm. The soils were a poorly drained Sharkey sc (Vertic Haplaquept) in northern Arkansas and moderately well drained Hebert sl (Aeric Ochraqualf) in southern Arkansas. Maximum grain sorghum yield occurred at a lower N rate on the silt loam soil than on the clayey soil in both years of the study. Based on soil inorganic N, th...

Performance of dicyandiamide in the north central states

Abstract The effectiveness of the nitrification inhibitors, nitrapyrin and dicyandiamine, in reducing nitrogen loss from soil and preventing reduction in crop yield was evaluated in field studies conducted over dozens of site years in Illinois, Iowa, Minnesota, and Wisconsin on corn, wheat, and a vegetable crop, potato. Both chemicals were effective in retarding the nitrification of ammoniacal fertilizers, including nitrogen from liquid animal manures, but this inhibitor did not always result in yield increases above that obtained with equivalent amounts of nitrogen applied without inhibitor. Greatest benefits for nitrification inhibitor use was obtained on coarse‐textured soils under conditions that were conducive to nitrate nitrogen loss when nitrogen was applied at rates not considered to be excessive.

OVERWINTER LOSSES OF NITROGEN-15 LABELLED UREA FERTILIZER

Field studies using 15N microplots were conducted to quantify the uptake and disappearance of fall- and spring-applied urea N on low organic matter, irrigated soils. Urea was mixed with the surface soil to maximize the potential for overwinter nitrification and subsequent losses of the fertilizer N. In three irrigated soils, losses of fall-applied urea averaged 24–31% compared with 11–21% of that applied at seeding. Barley took up 33–42% of spring-applied urea N but only 16–36% of fall-applied urea N. The lower uptake of fall-applied N apparently resulted from higher N losses rather than from the immobilization of fall-applied urea. Fall application resulted in lower soil reserves of residual fertilizer N after the growing season, as compared to spring application, in two of the three studies. Sixty percent of the fertilizer N recovered from the soil remained in the surface 15 cm. The application of 50 mm of water in the fall or 100 mm in the early spring, to intensify any effects of moisture, had a minimal effect on N losses or the distribution of N in the soil. This suggests that an individual rainfall event would not greatly affect the uptake or losses of fall-applied fertilizer on well-drained soil. The observed fertilizer losses, however, support practices such as concentrating fall-applied fertilizers in bands or the use of nitrification inhibitors. Key words: Denitrification, nitrogen, fertilizer, N balance, N losses, urea

Use of Nitrification Inhibitors and Ammonia Enrichment with Swine Manure Applications

A 3-yr study was conducted to determine the effects of inhibiting nitrification and addition of anhydrous ammonia on the fertilizer value of swine manure. Nitrapyrin (0.56, 1.12, 1.68 kg/ha), etradiazol (0.6, 1.2 kg/ha) and sodium methyl dithiocarbamate (1.2 kg/ha) were added to swine manure enriched with either 3.59 kg NH3/IOOO L for finishing, nursery and gestation house manure or 4.79 kg NH3/1000 L for farrowing house manure. All manures were injected in an Odell silt loam soil cropped to corn (Zea Mays L.) during fall or spring seasons at the rate of 28,062 to 30,868 L/ha for finishing, nursery and gestation house manure and 42,093 to 46,770 L/ha for farrowing house manure. Total nitrogen application rates on the manure plots ranged from 133 to 295 kg N/ha based on the corn plant requirement of 207 kg N/ha with a 7493 kg/ha grain yield. At above optimal nitrogen application levels, average corn yields were increased over 6% by addition of nitrification inhibitors. The beneficial effects of nitrification inhibitors on corn yields were greater when manure was applied in the fall compared to spring application. Over the entire study, adding 1.12 kg/ha of nitraprin or etradiazol to manure increased corn yields the most compared to other inhibitor levels or sodium methyl dithiocarbamate. Addition of 0.56 kg/ha of nitrapyrin in the fall also increased corn yields compared to manure applications without the inhibitor. Soil nutrient levels did not increase from the manure applications. Ammonia enrichment of the manure increased the proportion of the manure N in the NH4-N form. Lower stalk rot incidence and a trend towards increased N in grain and corn leaves were observed with the use of nitrification inhibitors.