Optimizing Nitrogen and Phosphor Use Efficiencies from Liquid Manure by Slurry Injection to Reduce Environmental Pollution

Abstract

The increase of livestock husbandry and the extension of biogas production in north-west Germany has led to a rising production of organic manure and an increasing acreage of maize. Although the nutrient demand of maize is more or less already covered by broadcast application of organic manure, usually a mineral nitrogen (N) and phosphorous (P) fertilizer (“starter fertilizer”) is side dressed to ensure proper early growth development. This fertilization practice often leads to nutrient surpluses which might be lost into non-agricultural ecosystems.Most recent techniques for slurry injection allow the banded application of liquid manures below the maize seeds. Due to high nutrient concentrations in the fertilizer band N immobilization and nitrification is reduced and roots have a better spatial access to the applied P. This might lead to an increased nutrient use efficiency from organic manures and the substitution of starter fertilizer without impairing maize yields and quality.In 2013 3-year field trials at eight sites (factorial block design, 4 replications) started in cooperation with the chambers of agriculture in Lower Saxony, North Rhine-Westphalia and Schleswig-Holstein to compare slurry injection (with/without addition of a nitrification inhibitor) versus broadcast application with starter fertilizer. During the vegetation period maize growth was assessed and at harvest yield, silage quality and nutrient uptake were determined. Compared to slurry broadcast application with starter fertilizer no significant differences in yield, quality or nutrient uptake were observed for slurry injection treatments. However, at least a trend to higher yield (+2% on average for 8 sites) and N-uptake (+3%) for slurry injection as well as a yield increase (+4%) and higher N-uptake (+6%) for slurry injection with nitrification inhibitor were found. Based on these preliminary results it can be concluded that slurry injection might lead to a reduced N and P input for maize growing.