Long-term fertilisation strategies and form affect nutrient budgets and soil test values, soil carbon retention and crop yield resilience

Abstract

The aim of this study was to evaluate the effects of long-term mineral and organic fertilisation on crop performance and soil fertility. The Long-Term Nutrient Depletion Trial (Denmark) was used to analyse changes in concentrations of Olsen-P, exchangeable potassium (K) and soil carbon (C). Yield responses (2010–2016) were evaluated making use of an early-season temperature model, fertilisation practices were evaluated by nutrient budgets, and nitrogen use efficiency by calculation of apparent recovery (ANR) in subplots receiving mineral N. Olsen-P (r2 = 0.68, P < 0.001) and exchangeable K (r2 = 0.86, P < 0.001) were correlated with the nutrient budgets. Soil C concentrations increased from 10.0 g kg−1 (1995) to between 11.1–14.6 g kg−1 (2016), with the greatest accumulation under slurry applications (P < 0.05, equalling 17–47% retention of slurry-C inputs). Relative yield responses of spring barley were associated with early season cold stress, but the model was not applicable to other crops. Increases of ANR in response to long-term phosphorus (P) applications were not significant. Balanced fertilisation is an effective way to maintain nutrient availability, and to ensure high and stable crop productivity and efficient use of nutrients. Direct C inputs from animal slurry are a major driver for increases of soil C concentrations.