Fertilizer replacement value and leaching of nitrogen applied to spring barley in cattle deep litter: A 3-year lysimeter study

Abstract

On farms with intensive animal production, manure represents a significant source of nitrogen (N) in crop production. Cattle deep litter is a common manure type in Denmark due to concerns regarding animal welfare. With a low ammonium to total N ratio, large quantities of deep litter are needed to meet crop N requirements. However, documentation regarding the N fertilizer value of deep litter and its effects on nitrate leaching losses needs further scrutiny. We investigated the N fertilizer effect of cattle deep litter in the year of amendment and in two residual years, and determined nitrate leaching losses in the two seasons following amendment, both with and without use of a cover crop.Spring barley (Hordeum vulgare) grew in outdoor lysimeters (1 m2 and 1.5 m deep) with two soil types, a loamy sand and a sandy loam. Crop N uptake was measured after incorporation of two rates of deep litter (362 and 725 kg total N ha−1), and compared with uptakes following mineral N fertilizer. After harvest, the lysimeters were vegetation-free or established with a cover crop (fodder radish, Raphanus sativus). The residual effect of the treatments was monitored in two following seasons.In the year of amendment (2017), crop yields in deep litter amended lysimeters were similar to those obtained with mineral N fertilizer on sandy loam while yields were lower on loamy sand. The N effect of the deep litter equaled its ammonium content on the loamy sand while it was higher on the sandy loam. The corresponding N fertilizer replacement value (NFRV) of manure total N was 9.7% and 16.2%. In the first residual year (2018), NFRV of the deep litter was 9.5% on the loamy sand and 6.8% on the sandy loam. The third year (2019) effect was small on both soils. In the first autumn-winter, marginal nitrate leaching of N was unaffected by type of amendment. It equaled 8.1% of total N applied when lysimeters were without a cover crop and 1.4% with a cover crop. In the second leaching season, marginal nitrate leaching was 4.6% of total N applied in the previous year.We conclude that deep litter can supply spring barley with sufficient N for optimal growth and has a considerable residual effect in the year after amendment. Marginal nitrate leaching was unaffected by N source and soil type, and nitrate leaching losses can be effectively reduced by introducing a cover crop.