Nitrogen Loss Research Joel Ransom NDSU Extension Agronomist

Background Nitrogen fertilizer third most costly input in corn production Nitrogen losses can be significant (only ~1/3 of N applied is used by the crop) Off site loses are environmental concerns

Why worry about N use efficiency? N is biologically and chemically very active in the soil Each N compound behaves differently in the soil affecting potential for loss Nitrous oxide is a potent greenhouse gas (impacts climate change?) Excess nitrate in surface waters causes eutrophication and anoxia

Wet cycle increases likelihood of N losses

Nitrification

Principles to guide N loss reductions 4 R’s of nutrient stewardship Right fertilizer source Right rate Right time Right place

Addressing sources of loss Volatilization Placement, urease inhibitors, polymer coated urea, soil moisture status (AA), application timing relative to rain (surface applications) Leaching and denitrification Delaying the conversions from ammonium to nitrate Nitrification inhibitors Soil temperature at time of application Polymer coated urea or slow release Banding vs. broadcasting Applying nearer the time of greatest uptake Slow release urea Split applications

Urease inhibitors NBPT is the most commonly available and widely tested (Agrotain, SuperU, etc.) Volatilization of NH3 from urea anytime moisture, urea and urease are present in temperatures that range from 11ºF to 105ºF. Urease inhibitors block the conversion of urea to ammonia for a period of one to two weeks allowing time for incorporation by rainfall or other means UAN contains 50% urea

Nitrification inhibitors Slow the conversion of NH4+ to NO3- by killing or reducing the activity of populations of Nitrosomonas and Nitrococcus bacteria. Two most common commercial inhibitors are nitrapyrin and DCD

Rate of nitrification Source: Schwab and Murdock, U of K

Goos, unpublished

Release rate of ESN compared to corn N uptake, Manitoba (Heard and Ginter, MAFRD).

Treatments included in recent research Standard treatment – urea pre-plant incorporated Instinct – new formulation of nitrapyrin that inhibits nitrification (ammonium to nitrate) Polymer coated urea – (ESN) coated so that it will release gradually and when temperatures are warmer (30% of total N applied) Split application – UAN applied at the 6 lf dribbled between rows Split with UAN + Agrotain Plus – urease inhibitor plus nitrification inhibitor in powder form for ease of mixing with UAN

Experimental locations 2011 two locations 2012 and 2013 five locations 2012 dry but productive year, limited N loss in most environments 2013 excess moisture early, dry later in the season

Effect of additive yield of corn, Fargo and Prosper, 2011.

Effect of nitrogen management practices on yield of corn in five environments, 2012.

Effect of nitrogen management practices at lowest N rate on yield of corn in five environments, 2012.

Effect of nitrogen management practices on yield of corn in five environments, 2013.

Effect of nitrogen management practices at lowest N rate on yield, all locations, 2013.

Effect of nitrogen management practices at lowest N rate on yield of corn in Casselton, 2013.

Prices Urea $550/ton ($60 per 100 lbs/N) ESN $675/ton ($73 per 100 lbs N = 22 lbs N) 28% UAN $360/ton ($64 per 100 lbs N) SuperU ~$660-690/ton (~$190 over price of urea) Instinct ~$11 per acre Agrotain $56 per ton ($6 per 100 lb N) Agrotain Plus $65 per ton ($11 per 100 lb N)

Conclusions No compelling evidence that additives were profitable in any of the environments included Split applications were both positive and negative depending on the environment Protection of UAN with urease inhibitor in one environment in 2013 Additional research would be beneficial to sample additional environments Rate of Instinct may need adjustment Ratio of ESN may have been too low to pick up response