Use and efficiency of a liquid nitrogen fertilizer on grassland

Abstract

Liquid nitrogen fertilizers are, per unit of N, generally cheaper than granulated ammonium nitrate because of lower production costs. Although very corrosive, the storage and handling of liquid nitrogen fertilizers does not usually present any problems. The applicability and efficiency of a commercial liquid nitrogen fertilizer (containing 39% N, half urea and half ammonium nitrate) on grassland was investigated in comparison with granulated ammonium nitrate (27% N). The liquid nitrogen fertilizer was applied on continuously grazed paddocks without any repercussions for animal health. No scorching was observed provided that certain measures were adopted while spraying the fertilizer: i.e. little dilution with water, use of low pressure and large droplets and application on dry grass in cloudy whether. In comparison with the granulated ammonium nitrate, the liquid nitrogen fertilizer was less efficient; dry matter yield and N-uptake of the grass treated with the liquid nitrogen fertilizer were 76% and 73% respectively of the dry matter yield and N-uptake of the grass treated with the granulated ammonium nitrate fertilizer.

Fertilization, especially with nitrogen, represents the biggest single cost in grass production. Because liquid nitrogen fertilizers can be produced less expensively then granulated ones, their price per unit of N, delivered to the farmer, is also lower.

Another advantage is that liquid fertilizers are easy to handle (despite being corrosive) and can be distributed uniformly over the field. The greatest advantage can be expected on the large grass areas of continuous grazing systems. Because of these benefits, an investigation was carried out to assess the potential use and efficiency of liquid nitrogen fetilizer in comparison with granulated ammonium nitrate nitrogen, from 1983 up to 1987. In 1983 and 1984, the grass quality, especially NH₃ and NO₃ concentration directly after spraying, and animal behaviour were assessed. From 1985 to 1987, the grass yield and nitrogen uptake were measured under mowing conditions.