Biochar can improve soil health and crop productivity. We studied the response of soil properties and wheat growth to four rates of wood biochar (0, 11.2, 22.4, and 44.8 Mg ha⁻¹) and two fertilizer rates [no fertilizer and fertilizer (90 kg N ha⁻¹, 45 kg P ha⁻¹, and 20 kg S ha⁻¹)]. Biochar application increased soil organic matter (SOM), soil pH, phosphorus (P), potassium (K), sulfur (S) contents, and the shoot and root biomass of wheat. However, these responses were observed at biochar rates below 22.4 Mg ha⁻¹, particularly in treatments without fertilizer. In fertilizer-applied treatments, soil nitrate levels decreased with an increase in biochar rates, mainly due to better crop growth and high nitrate uptake. However, without N addition, the high C:N ratio (500:1) possibly increased nutrient tie-up, reduced plant biomass, and SOM buildup at the highest biochar rate. Based on these results, we recommend biochar rates of about 22.4 Mg ha⁻¹ and below for Walla Walla silt loams.

Core Ideas: Effect of cover crops on selected soil health indicators and wheat yield was monitored. Response of soil organic matter pools varied with cover crops and sampling dates. Oat and its mixtures as cover crops have potential to improve soil health. Cover cropping has a potential to improve soil health in semiarid regions. This research evaluated the effects of spring‐planted cover crops on selected soil health indicators in limited‐irrigated winter wheat (Triticum aestivum L.)–fallow system. Soil health parameters measured include soil water content (SWC), soil organic carbon (SOC), soil total nitrogen (STN), potentially mineralizable carbon (PMC), potentially mineralizable nitrogen (PMN), permanganate oxidizable carbon (POXC), inorganic N, and available P. Cover crops tested were pea (Pisum sativum L.), oat (Avena sativa L.), canola (Brassica napus L.), pea + oat (PO), pea + canola (PC), pea + oat + canola (POC), pea + oat + canola + hairy vetch (Vicia villosa L.) + forage radish (Raphanus sativus L.) + barley (Hordeum vulgare L.) (SSM), and a fallow. Cover crops were planted in February and terminated in May after 85 to 90 d. Cover crop biomass was 33 to 142% greater with oat, PO, PC, POC, and SSM than pea and canola. The SWC was 2 to 3% lower under cover crops than fallow plots at their termination, but was 2 and 4% greater in SSM and POC than fallow at wheat planting in October. Soil inorganic N was 41 to 49% lower with cover crops than fallow at termination date. Soil PMC and POXC varied with cover crop species and sampling dates. The SOC and STN contents were 18 to 20% greater with oat than PC. Oat and its mixture with other cover crops show promises to improve soil health and resilience.

Decline in soil organic carbon (SOC) and the associated impacts on crop production under conventional farming raises concerns on how alternative management practices increase SOC sequestration and improve agricultural sustainability. This study aimed to understand SOC mineralization kinetics with different cover crop (CC) residue amendments. Soil samples were collected from a fallow and three CC (pea, oat, and canola) plots. Soil samples from the CC plots were manipulated with zero, five, and 10 Mg ha⁻¹ of the respective CC residues. All soil samples were incubated for eight weeks, SOC mineralization was monitored, and the first order kinetic and parabolic equation models were fitted to the observed data for estimating labile SOC (C₀), and the decomposition rate constant (k). Subsequent comparisons of fitted model parameters were based on the first order kinetic model. The C₀ varied with the residue amount while k varied with CC type. C₀ was 591–858% greater with 10 Mg ha⁻¹ and 289–456% greater with five Mg ha⁻¹ residue additions while k was 122–297% greater with 10 Mg ha⁻¹ and 94–240% greater with five Mg ha⁻¹ residue additions when compared to the fallow treatment. The CC residue stimulated cumulative carbon mineralization (C_min) irrespective of CC type, suggesting that cover cropping has potential to improve SOC cycling in agroecosystems.