The influence of climate and management on surface soil health within the Inland Pacific Northwest

Jason G. Morrow

Surface soils influence ecosystem health through their role in nutrient cycling and decomposition, gas exchange, water infiltration, and erosion. Soil organic matter (SOM) is critical to soil functioning and subsequently to soil and ecosystem health. Across four dryland sites and one irrigated site within the inland Pacific Northwest (PNW), the objectives were to assess the influence of climate, tillage, and cropping intensity on surface soil health by measuring soil C and N properties related to SOM as well as nutrient availability (NO3 - , NH4 + , Ca, Mg, P, K, S, Mn, Fe, Zn, B, Cu) quantified by PRSTM probes (Western Ag Innovations, Saskatoon, Canada). A multivariate regression of mean annual temperature (MAT) and precipitation (MAP), tillage, and cropping intensity revealed that MAP explained 57% of soil organic carbon (SOC) variability and 69% of total soil N variability. When MAP was removed from the model, MAT explained 42% and 49%, respectively, of SOC and total N variability. Both the hydrolyzable and non-hydrolyzable fractions of SOC were equally sensitive to climate, indicating no relationship between chemical recalcitrance and climate sensitivity. Permanganate oxidizable carbon (POXC) was representative of SOM stabilization, while one-day carbon mineralization was v representative of microbial activity and SOM mineralization. Both POXC and mineralization potential may be increased by cropping diversification, and stabilized inputs, such as compost, along with no-till, may increase POXC. An increase in MAT across the region was associated with a decrease in potential nitrogen mineralization (PNM) (r = -0.73), potential denitrification (PDR) (r = -0.66), and basal denitrification (BDR) (r = -0.34). An increase in MAP was associated with an increase in PNM (r = 0.60) and PDR (r = 0.55), but was not related to BDR. Tillage intensity was correlated with PNM (r = -0.32), PDR (r = 0.32), and BDR (r = 0.32), whereas cropping intensity was correlated only with PNM (r = 0.40). Plant available nutrients displayed varying correlations with soil C and N properties, management, and climate factors. Overall, POXC and carbon mineralization were the most important indicators of surface soil health.

The influence of climate and management on surface soil health within the Inland Pacific Northwest

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