Long-term manure application to improve soil macroaggregates and plant-available nitrogen in a Mollisol

Long-term incorporation of manure has shown many benefits to improve soil productivity, but its effects on nitrogen (N) partitioning in aggregates and availability plants is not well understood. The aim this study was examine the influence different long-term field fertilization regimes N aggregates. Soils from a after 25-yr treatments no (CK), mineral fertilizer (NPK), NPK with stover return (NPKS), application (NPKM) were examined for adding 15N-labelled urea incubating 42 days. Using wet sieving procedure, separated into macroaggregates (> 250 ?m, coarse particulate organic matter or cPOM), microaggregates (53–250 ?m), silt + clay (< 53 inter mineral-associated OM inter-MOM). further fine free POM (ffPOM), physically protected intra-aggregate (iPOM), intra (intra-MOM). Total 15N concentrations determined. All fractions except ffPOM (limited mass) used cultivate ryegrass (Lolium perenne L.) uptake Mass macroaggregate 10 % higher NPKM NPKS significantly use efficiency than that while opposite true intra-MOM fraction differences other fractions. retained cPOM, intra-MOM, inter-MOM ranged 24 34%, 28–37 %, 33–38 respectively, iPOM 1–4% all Ryegrass range 14–19 14–24 3–5% inter-MOM, respectively. However, total amount treatment (14 %) lowest due (86 15N) as soluble phase compared (78–83 %). This research concludes resulted increased formation macroaggregates, plant-available aggregates, larger contributed high yield illustrating role productivity sustain crop production.