Do post-harvest crop residues in no-till systems provide for nitrogen needs of following crops?

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.