Agricultural soils have a C:N ratio of around 10-13:1. What would happen to the available N in these soils if straw (C:N of 40:1) were added to them?

Question

Agricultural soils have a C:N ratio of around 10-13:1. What would happen to the available N in these soils if straw (C:N of >40:1) were added to them?

BlackTom AI · Accepted Answer

Question restatement: The soil has a typical agricultural C:N ratio of about 10–13:1. If straw, which has a high C:N ratio (>40:1), is added to such soil, what happens to the soil’s available nitrogen (N)?

Option 1: Nitrogen from the soil available N pool will be temporarily immobilized. This is the core concept: when a carbon-rich material with a high C:N ratio is added, soil microbes decompose it but require additional nitrogen to build their own biomass. Since the straw provides relatively little N, microbes scavenge N from the soil's mineral N pool, converting it into microbial biomass and thereby reducing the pool of readily available inorganic N temporarily. This immobilization means less N is available for plant uptake in the short term.

Option 2: There is an increase in soil available N pool due to mineralization of straw and release of mineral N to soil. This would be true if the substrate had a favorable C:N ratio (low enough) or if microbial activity released N; however, with straw’s very high C:N, microbial metabolism tends to immobilize N rather than mineralize it, at least in the short term. Therefore this statement contradicts the typical immobilization process observed with high-C substrates.

Option 3: There is no effect on the mineral N pool. In reality, the addition of a high-carbon material often causes a measurable shift in the N pool due to microbial uptake for biomass synthesis. Saying there is no effect ignores the well-documented immobilization response that accompanies high C:N inputs, making this option inaccurate.

Additional context: The balance between carbon inputs and nitrogen availability governs whether mineralization or immobilization dominates. High C inputs relative to N (as with straw) generally drive immobilization, slowing N mineralization temporarily until microbial turnover and straw decomposition progress.

Summary of why option 1 is correct and the others are not: The introductory C:N mismatch (straw >40:1 vs soil 10–13:1) creates demand for soil N by microbes, leading to temporary immobilization, whereas option 2 describes mineralization that is unlikely under these conditions, option 3 ignores the expected microbial N uptake dynamics under high-C input.

Agricultural soils have a C:N ratio of around 10-13:1. What would happen to the available N in these soils if straw (C:N of >40:1) were added to them?单项选择题

类似问题

以下哪张图属于私密照片？

What is difference between ‘disclosures’ and ‘complaints’ at the University of Sydney?

Which of the following best describes intersectionality in the context of understanding relationship dynamics?

28岁的杰米患有精神分裂症，经常出现妄想和思维混乱。一天晚上，他和伴侣泰勒在沙发上讨论性行为。杰米似乎心不在焉，难以清晰地表达自己的想法。哪些因素可能会影响杰米做出知情同意的能力？

What are some barriers international students might face when reporting sexual harm or gender-based violence?

Which scenario best demonstrates an unhealthy power imbalance in a relationship?

更多留学生实用工具

智能学习助手

风格化写作助手

论文查重助手

文献引用助手

课堂转译助手

课堂笔记助手

Quiz搜索助手

学校历年真题

智能刷题助手

智能匹配练习

希望你的学习变得更简单