Selenium Uptake and Maize (<i>Zea mays</i> L.) Growth as Affected by Different Rates and Forms of Nitrogen

ABSTRACT Background Selenium (Se) concentration is low in animal meat and human beings due to its insufficient levels in forage and feed sources. Aims This study investigates the effects of nitrogen (N) rates and N forms to improve the biomass and Se concentration in maize forage. Methods The soil in the pots was fertilized with N at the rates of 165 and 330 mg kg −1 without and with 3,4‐dimethylpyrazole phosphate (DMPP). DMPP was added to soil at the rate of 0.01% of added N, whereas Se was added at the rate of 40 µg kg −1 . In the following experiment, the effect of N forms (NH 4 + ‐N, NO 3 − ‐N and NH 4 + ‐N +O 3 − ‐N) was evaluated on the growth and the accumulation of Se, N and phosphorus (P) in maize shoots in Se‐fertilized (40 µg kg −1 ) and control soils. The Se‐fertilized and controls soils were designated as Se(+) and Se(−), respectively. The soil texture was sandy and its pH was moderately acidic (5.40). Results The DMPP‐treated soil had 27%–42% higher NH 4 + ‐N content at harvest than the non‐treated soil. The DMPP treatment of soil also increased shoot Se content by 19%–23% and Se uptake by 37%–42%. A negative correlation was found between NO 3 − ‐N: NH 4 + ‐N ratio and shoot Se uptake, suggesting that NO 3 − ‐N negatively affected Se uptake by maize. Results of second experiment depicted that applying NH 4 + ‐N led to higher shoot Se content and uptake than NO 3 − ‐N. In case of Se‐unfertilized soil, adding NH 4 + ‐N produced 14% and 56% more shoot Se content and uptake, respectively, whereas these increases were 39% and 83% on Se‐fertilized soils. Similar to Se uptake, plants fed with NH 4 + ‐N had higher P and N uptake by maize shoots than that fed with NO 3 − ‐N. The SPAD value and shoot biomass were also higher by applying NH 4 + ‐N than NO 3 − ‐N. Conclusion These results imply that N fertilization, specifically combined application of Se and ammonium‐based fertilizers could improve biomass yield and Se content of maize, which is likely to yield maize grains with improved Se contents.