Split application of stabilized ammonium nitrate improved potato yield and nitrogen-use efficiency with reduced application rate in tropical sandy soils

Authors: SOUZA, EMERSON - University Of Minnesota; SORATTO, ROGERIO - Sao Paulo State University (UNESP); SANDANA, PATRICIO - Universidad De Chile; Venterea, Rodney - Rod; ROSEN, CARL - University Of Minnesota

Submitted to: Field Crops Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/12/2020
Publication Date: 9/1/2020
Citation: Souza, E.F., Soratto, R.P., Sandana, P., Venterea, R.T., Rosen, C. 2020. Split application of stabilized ammonium nitrate improved potato yield and nitrogen-use efficiency with reduced application rate in tropical sandy soils. Field Crops Research. 254. https://doi.org/10.1016/j.fcr.2020.107847.
DOI: https://doi.org/10.1016/j.fcr.2020.107847

Interpretive Summary: Urea is the dominant nitrogen (N) fertilizer used for potato (Solanum tuberosum L.) cultivation in most parts of the world. Fertilizers containing nitrification inhibitors (NIs) claim to improve performance of crops including potato. No studies to date have conducted comprehensive assessment of the effectiveness of NIs under varying N rates or application timings to enhance potato yield, tuber quality or N-use efficiency (NUE) in tropical regions. Three field experiments were conducted on irrigated sandy soils in southeastern Brazil to determine whether single or split application of ammonium sulfate nitrate (ASN) with the NI 3,4-dimethylpyrazole phosphate (DMPP) at reduced (75%) or recommended N rates (RNR, 100% = 160 kg ha-1) could improve yield, quality and/or NUE of ‘Agata’ potato over conventional split-applied urea at 100% of RNR. Compared to the conventional practice, split-applied ASN+DMPP, at either 75% or 100% of RNR, increased fresh tuber yield by an average of 15% across all site-years, and reduced N surplus in site-years with greater rainfall events suggesting that reactive N losses to the environmental were also reduced. With split-applied ASN+DMPP at 75% of RNR, fresh tuber yield per unit of applied N increased by 34% compared to split-applied ASN+DMPP at 100% of RNR, and by 50-75% compared to a single application of ASN+DMPP at planting. These results demonstrate a mutually beneficial opportunity, where the rate of split-applied ASN+DMPP can be reduced by 25% while at the same time increasing yields, thus resulting in agronomic, economic and environmental benefits due to the decreased potential for off-site losses of reactive N. The findings of this study will assist producers and policy makers in developing and implementing improved practices that enhance crop production and resource use efficiency while reducing potential environmental impacts.

Technical Abstract: Urea is the dominant nitrogen (N) fertilizer used for potato (Solanum tuberosum L.) cultivation in most parts of the world. Fertilizers containing nitrification inhibitors (NIs) claim to improve performance of crops including potato. No studies to date have conducted comprehensive assessment of the effectiveness of NIs under varying N rates or application timings to enhance potato yield, tuber quality or N-use efficiency (NUE) in tropical regions. Three field experiments were conducted on irrigated sandy soils in southeastern Brazil to determine whether single or split application of ammonium sulfate nitrate (ASN) with the NI 3,4-dimethylpyrazole phosphate (DMPP) at reduced (75%) or recommended N rates (RNR, 100% = 160 kg ha-1) could improve yield, quality and/or NUE of ‘Agata’ potato over conventional split-applied urea at 100% of RNR. Compared to the conventional practice, split-applied ASN+DMPP, at either 75% or 100% of RNR, increased fresh tuber yield by an average of 15% across all site-years, and reduced N surplus in site-years with greater rainfall events suggesting that reactive N losses to the environmental were also reduced. With split-applied ASN+DMPP at 75% of RNR, fresh tuber yield per unit of applied N increased by 34% compared to split-applied ASN+DMPP at 100% of RNR, and by 50-75% compared to a single application of ASN+DMPP at planting. These results demonstrate a mutually beneficial opportunity, where the rate of split-applied ASN+DMPP can be reduced by 25% while at the same time increasing yields, thus resulting in agronomic, economic and environmental benefits due to the decreased potential for off-site losses of reactive N.