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

Abstract

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.

Post‐harvest crop residue contribution to soil N availability or unavailability in North Dakota

“…An observation of immobilization of NO 3 -N by nonleguminous post-harvest crop residues is consistently observed in our studies and is supported by other studies (Alghamdi & Cihacek, 2021). Kaur et al (2018) observed similar results in other North Dakota soils in short-term incubations.…”

“…However, in cooler climates with highly variable precipitation, the rate of residue decomposition is less predictable, resulting in less certain N mineralization. This brings to question if changes are necessary in N management for no-till production in the cooler climates of the northern Great Plains and other parts of the United States (Alghamdi & Cihacek, 2021). Research in the region has not yet validated N availability of specific crop residues, which is essential to determine if producer fertilizer application needs are being met.…”

Effects of fertilizer type on nitrous oxide emission and ammonia volatilization in wheat and maize crops

“…The balance of the competition for N in the soil between plants and microbes (Inselsbacher et al, 2010; Kuzykov & Xu 2013; Shimel & Bennet, 2004) influences N 2 O emissions. Microbial N demands can be increased after N fertilization because of the interaction between crop residues and the soil (Alghamdi & Cihacek 2021; Wang et al, 2021) and low plant cover contributes to high N availability. But, because of the short life cycle of rhizosphere microorganisms and the insufficient C to maintain its fast initial growth rates, N is released into the soil, becoming available for growing plants (Jacoby et al, 2017; Richardson et al, 2009).…”

Cover crop residue influence on soil N2O and CO2 emissions under wetting‐drying intensities: An incubation study

“…The average$$$ {\mathrm{NH}}_4^{+} $$$:$$$ {\mathrm{NO}}_3^{-} $$$ ratio under wetting to 70% WFPS was 1.6 for winter wheat while it was 1.0 for crimson clover (Table 2). Limited nitrification or greater $$$ {\mathrm{NO}}_3^{-}\hbox{--} \mathrm{N} $$$ immobilisation perhaps reduced soil $$$ {\mathrm{NO}}_3^{-}\hbox{--} \mathrm{N} $$$ availability during winter wheat residue decomposition (Alghamdi et al, 2022; Alghamdi & Cihacek, 2022). Therefore, $$$ {\mathrm{NO}}_3^{-}\hbox{--} \mathrm{N} $$$ limitation perhaps influenced a lower rate of N 2 O production from nitrification and denitrification under winter wheat with greater potential for complete denitrification to reduce N 2 O to N 2 in presence of available C (Table 2).…”