Performance of conventional and enhanced-efficiency nitrogen fertilizers on potato tuber mineral composition and marketability

BACKGROUND: Potato is an essential crop for global food security, and its cultivation requires a significant amount of readily available nitrogen (N) to ensure tuber quality. Therefore, managing N with enhanced-efficiency fertilizers becomes a potential strategy to meet the seasonal potato N demand. A 3 site-years (SYs) study was conducted to assess the marketable attributes and mineral composition of table-stock potato in response to N rates and fertilizers urea, ammonium sulfate and ammonium sulfate nitrate (ASN) with nitrification inhibitor dimethylpyrazole phosphate (DMPP). RESULTS: At 75% of recommended N rate (RNR), ammonium sulfate and ASN+DMPP ensured marketable tuber yields equivalent to that observed at 100% of RNR. Urea promoted greater tuber K and Mg concentrations than ammonium sulfate and ASN+DMPP. Although inconsistent across SYs, ASN+DMPP generally reduced starch and reducing sugars contents and increased pulp pH and protein content than other fertilizers. Increasing N rates from 50% up to 75% and 100% of RNR increased marketable tuber yields and protein content, whereas soluble solids increased from 50% to 100% of RNR. Conversely, increasing N rates from zero to 75% of RNR reduced tuber firmness, whereas N application reduced tuber P concentration, regardless of N rates. CONCLUSION: Although ASN+DMPP showed potential for increasing marketable tuber yield and protein content, potatoes receiving ammonium sulfate and ASN+DMPP lowered tuber K and Mg concentrations compared to those receiving urea. Overall, potato tuber quality improvements are N source-specific, demanding strategies under which these fertilizers can ensure/improve tuber nutritional composition along with size quality.