Soil health indicators and crop yield in response to long-term cropping sequence and nitrogen fertilization

Abstract

There is a need for including soil physical and biological properties along with chemical properties to accurately measure soil health and relate to crop yields. The objective of this study was to determine a suite of soil health indicators that were sensitive to cropping systems and N fertilization and relate to soil properties and dryland crop yield in a 14-yr-old cropping sequence and N fertilization study in eastern Montana, USA. Main-plot (cropping sequence) treatments were conventional till barley (Hordeum vulgaris L.)/spring wheat (Triticum aestivum L.)-fallow (CTWF), no-till continuous barley/spring wheat (NTCW), no-till barley/spring wheat-fallow (NTWF), and no-till barley/spring wheat-pea (Pisum sativum L.) (NTWP) and split-plot (N fertilization) treatments were 0 (N0) and 80/100 kg N ha−1 (N1) applied to barley and spring wheat. Barley was grown for the first six years that was replaced by spring wheat for the last eight years. The NTCW increased aggregate stability, wet aggregate stability index, average slake aggregate, P concentration, KMNO4-extractable C, CO2 flush (1 d incubation), potentially mineralizable N, and N-acetyl β-glucosaminidase (NAG), but reduced NO3-N concentration compared to other treatments. Water-stable aggregation, macro-porosity, volumetric water content at water saturation, and Mg concentration were greater with N0, but water-extractable total N and NO3-N concentration were greater with N1. Mean crop (barley/spring wheat) yield from 2006 to 2019 were greater in NTCW with N1 than other treatments. Multivariate analysis showed that phospholipid-derived fatty acid (PLFA) and CO2 flush at 4-d incubation were negatively related to Ca and Al concentrations, but positively to crop yield. Microbial abundance and activity can be used as important soil health indicators that were enhanced by no-tillage with increased cropping intensity and related to crop yield.