Soil nitrogen dynamics and crop residues. A review

Abstract

International audienceNitrogen (N) is a major fertiliser for agriculture and food production. About 67.84 million tons of N are annually applied to agricultural fields, without which nearly half of the world’s population would not be alive today. Returning plant residues to the soil is an alternative and sustainable way of N fertilisation. Although impacts of returning plant residues on plant available N in soil have been widely studied, there is still no systematic review of their mechanisms and models. In this review we highlight the following advances: (1) When plant residues are returned to the soil, N undergoes biotic immobilisation–remineralisation, abiotic immobilisation, soil organic N mineralisation and plant residue organic N mineralisation. (2) Plant residues modify inorganic N fate using three mechanism mineralisation, immobilisation–mineralisation and immobilisation, depending on plant residue nature and soil properties. (3) The use of plant residue C/N ratio is not always effective to predict the effect of plant residues. Instead, soil properties and the forms of carbon and nitrogen should be considered. (4) Mineralisation always promotes N uptake by crops and increases the risk of N loss. In addition, although net immobilisation is involved in immobilisation–mineralisation and immobilisation, it does not necessarily induce lower crop nitrogen uptake. Results also depend on the synchronism between the changing soil inorganic N and the crop N uptake. (5) N loss during mineralisation can be reduced by an immobiliser. Net N immobilisation during immobilisation–mineralisation and immobilisation can be reduced by changing the timing of ploughing and fertilising or by changing the plant residues placement

Carbon Inputs from Miscanthus Displace Older Soil Organic Carbon Without Inducing Priming

“…Kaňová et al [95] also observed that rhizosphere respiration under Miscanthus was limited by nitrogen, potassium and calcium, further reinforcing the idea that a lack of priming in our study may, in part, be due to the high C:N of Miscanthus biomass. Other studies have also suggested a mechanistic links between N-availability and priming SOM decomposition [96,97]. Rhizospheric priming in particular is intrinsically linked to Nmineralisation, with the extent of live root biomass being strongly linked to the microbial activity associated with decomposition.…”

Recycling nutrients from horse manure: effects of bedding type and its compostability

“…Horse manure typically has a high carbon (C) to N (C:N) ratio, meaning that decomposing microbes absorb released N to satisfy their growth requirements (Chen et al 2014). Due to this net N immobilization, horse manure is not a desired fertilizer.…”

Crop residue management and fertilization effects on soil organic matter and associated biological properties

“…In addition, returning crop residues to fields rather than burning them is strongly encouraged by the government of China and environmental scientists to mitigate air pollution and improve nutrient availability in agricultural ecosystems (Chen et al 2006;Chen et al 2014).…”

“…Although there are many studies on changes in soil microbial community and nutrient dynamics by manure and crop residues return (e.g. Zhao et al 2013;Chen et al 2014), few studies have documented linkages between the changes in soil nutrient availability and soil quality indicators with alterations in functioning and composition of soil microbial community in a field with crop residues return in the first few years. Moreover, it is impossible in real practice when all N is applied using the organic manure due to its high cost.…”