Increased adoption of no‐till systems in the Northern Plains has led to an increased volume of post‐harvest crop residue. A cool climate coupled with short growing seasons benefits from a conservation tillage approach by increasing water storage in semi‐arid areas where weather conditions are variable each year. The short frost‐free period presents challenges for residue decomposition and the subsequent nutrient uptake period is reduced in heavy accumulated crop fields. A combination of soil management practices can be used to optimize nutrient utilization, particularly for nitrogen (N), including the use of cover crops, crop rotation and diversification, and variances in fertilizer form, method, and timing. Despite many management practices being effective in conserving N in the soil, they still may not meet nutrient demands for succeeding crops in short season and water‐ and N‐limited environments. Decomposition of crop residue is dependent on soil moisture, soil temperature, and the carbon/nitrogen (C/N) ratio of crop residue. Generally, post‐harvest crop residues have a wider C/N ratio than aged residue that accumulates on the soil surface over time. Adding fertilizer N may reduce the immobilization of nutrients near the soil surface of a post‐harvest residue in heavily accumulated crop fields, making it more available for utilization by plants. Recommendations for fertilizer N rates are inconsistent throughout the northern US for long‐term no‐till systems. This review highlights several decades of known research yet points to the continued gaps needed for producers to fully support fertilizer N recommendations for no‐till systems in temperate climates.

Core Ideas Hydromulch was applied to disturbed, bare soil at two rates. Micro‐Bowen ratio systems quantified soil temperature and evaporation. Hydromulch moderated temperature fluctuations, especially daily maximums. Hydromulch application reduced evaporation following rainfall. North Dakota State Univ., Dep. of Soil Science, Fargo, ND 58108. Soil disturbance reduces plant‐residue cover and can leave bare soil susceptible to erosion, extreme temperature fluctuations, and increased evaporation. Under such conditions, establishing vegetation is difficult. To overcome these difficulties, managing disturbed lands by applying surface cover may be a good step toward soil reclamation. Hydromulch is often applied to stabilize soil after disturbance, but its influence on soil temperature and evaporation has not been described. This study assessed soil temperature over time and used the surface energy balance to quantify evaporation from bare soil (0×), and two rates of hydromulch application, 1× and 3× (by weight) of manufacturer's recommended rate. Diurnal temperature extremes were highest in the 0× and least in the 3×. Evaporation was highest in the 0× during the final 18 d of data collection and lowest in the 3×. These findings indicate that temperature fluctuations decrease and evaporation is reduced when hydromulch is applied to bare soil, suggesting it may aid in soil reclamation.

In the US upper Midwest, the narrow growing season causes many farmers to presume yield losses when reducing tillage. The purpose of this study was to determine how four production-scale tillage systems affected residue cover, stand populations, crop yields, and soil chemical, biological, and physical properties. Tillage systems (chisel plow, fall strip-till with shanks, spring strip-till with coulters, and shallow vertical till) were continued for 4 yr. Tillage effects within a site were few and mixed (0.17-0.36 Mg ha-1 difference), whereas site effects were common (0.50-3.00 Mg ha-1 difference). Among 19 soil properties, only fungal/bacteria ratios differed among strip-till with shanks (0.078) and strip-till with coulters (0.066) at one site. Our results suggest that many farmers' concerns about using conservation tillage practices do not necessarily translate into yield losses when compared to standard chisel plow practices. Economics and the level of erosion control among the tillage practices compared here, rather than yield alone, should guide farmer preferences.

North Dakota producers have adopted conservation tillage practices to conserve soil moisture and reduce wind and water erosion. As a result, an accumulation of crop residue has been observed but current recommendations encourage a fertilizer N credit in fields under no-till for more than 6 yr. Producers are concerned that postharvest crop residues are not contributing to N needs of subsequent crops during the growing season. This study was established to assess N mineralization from common crop residue in conventional tillage systems using long-term incubation studies in order to establish a baseline for future studies on no-till systems. Three commonly cultivated North Dakota soil series were selected for study with seven residue treatments (varying C/N ratios) including corn (Zea mays L.), soybean [Glycine max (L.) Merr.], flax (Linum usitatissimum L.), forage radish (Raphanus sativus L.), winter pea (Pisum sativum L.), spring and winter wheat (Triticum aestivum L.), and a soilonly control. Biweekly leachings were collected for nine incubation periods and analyzed for nitrate-nitrogen (NO 3 -N). Soils with higher organic matter (OM) resulted in increased soil N mineralization (Fargo [1.63 mg kg -1 N] > Forman [0.65 mg kg -1 N] > Heimdal-Emrick [0.38 mg kg -1 N]). Radish and pea residues (narrow C/N ratios) were the only treatments showing N mineralization potential compared with the soil only controls. However, post-harvest residues with wide C/N ratios (>25:1) promote N immobilization when compared with mineralization by the soil alone. These findings raise the question of whether the N credits for >6 yr of no-till management are appropriate in the northern Great Plains.