Studies on the Nitrogen Use Efficiency (NUE) of Spring Applied Liquid Pig Manure to an Irish Winter Wheat crop.

The disposal of animal waste products is an on-going problem on specialised livestock farms including intensive pig (hog) enterprises. Exporting product to farms including cropping-based farms with nutrient deficits offers one solution.  Separation of this pig manure into liquid and solid fractions offers different organic-based ‘fertilisation’ products for utilisation in intensive crop-based production systems. This study examines the nitrogen (N) replacement value of the separated liquid (SLPM) fraction when applied to winter wheat crops in spring. Field experiments were carried out in 2007 and 2008 at 2 locations, a clay-loam site in Dublin (cv. Alchemy – 2007, cv. Lion – 2008) and a sandy-loam site in Carlow (cv. Cordiale). In a 2 x 5 factorial experimental design (2 SLPM rates and 5 chemical N rates) with 4 replications, the manure product (4% N) was applied at a rate of 30,000 l/ha using a modified sprayer to span individual plots (1.8m*20m) at G.S 30-31. Grain and straw N uptakes were analysed to calculate total crop N uptake (CNU) and NUE at harvest, grain yield and grain protein were also recorded. Crop response to both the organic and inorganic N was poor in both seasons, primarily attributed to a period of prolonged moisture deficit in late-spring (GS 32-37) and followed by a wet summer period during grain filling which resulted in below average grain yields. In 2007 significant grain yield and CNU increases (P<0.05) were recorded in Carlow site but not Dublin. A similar weather pattern occurred in 2008 but increases (P<0.05) in CNU, grain yield and grain N% were recorded to SLPM treatments at both sites. These experiments indicate that SLPM can be applied successfully to winter wheat crops in spring and can make a significant contribution to the N requirements for the crop in combination with an appropriate fertiliser N application.