Welcome to part nine of the column series on soybean micronutrients. The past several weeks I discussed boron, chloride, cobalt, copper, iron, manganese, and molybdenum. I will quickly cover how nickel (Ni) is essential to soybeans, known deficiencies or toxicities in the region, factors of nickel availability in soil, soil and plant tissue testing, and fertilizer recommendations. Micronutrients for Soybean Production in the North Central Region is a good regional publication that addresses nickel that I utilized as a resource for this news column.
In soybeans, nickel is a key micronutrient for nitrogen metabolism of urea-like compounds and can benefit symbiosis between Rhizobia bacteria and soybeans. Nickel was not determined to be an essential micronutrient until 1987. Nickel deficiency symptoms include browning of leaf tips because of toxic levels of the urea-like compound accumulating. Nickel deficiency has not been observed in soybean or any other crop in the north-central United States. Nickel toxicity symptoms are actually similar to iron deficiency chlorosis. Nickel accumulation in plants or toxicity would most likely occur through over application from some land-applied biosolids, but heavy metals concentration in biosolids can be quite different.
Soybeans take up nickel as a cation (Ni2+) from the soil similar to zinc and copper. Nickel is found in soil minerals and held by the cation exchange capacity of the soil. High soil pH above 7.0 to 7.5 will make nickel less available to soybeans. Due to both Rhizobia bacteria and soybeans, it is beneficial to maintain soil pH above 6.0 and closer to a pH of 6.5 to maximize yield potential. Elevated levels of zinc, copper, or nickel could influence or reduce uptake of the other. Nickel soil and tissue testing is not routine. Special heavy metal analysis (EPA 503 package) for nickel would cost around $215. Based on my work in Dodge County with the City of Fremont Biosolids, soil nickel concentrations prior to application were around 20 part per million (ppm) and the biosolids nickel concentration was only 30 ppm. This means Fremont Biosolids were low or not likely to change soil nickel concentrations.
Similar to molybdenum, the amount needed by soybeans is truly micro or small, with most plants only containing 1 ppm in tissue. There is no published research in this area on nickel and no current agronomic soil and tissue testing available. It is very unlikely that nickel is a concern for us in southeast Nebraska and we have many other agronomic challenges to address. If you are still concerned about nickel, I encourage you to conduct your own on-farm research through the UNL On-Farm Research Network by contacting me. I look forward to writing about zinc in next week’s column. You can share or read this news column online through my local website for Saline, Jefferson, and Gage counties at croptechcafe.org. Know your crop, know your tech, know your bottom line.
