Nitrogen Fixation and Transfer in Agricultural Production Systems

Abstract

There is a consensus within the scientific community that nitrogenous fertilizers are almost indispensable in today's agriculture. However, the geometric increase in nitrogenous fertilizer applications and the associated environmental concerns call for focus on more sustainable alternatives. Biological dinitrogen (N 2 ) fixation (BNF) is one of the most sustainable approaches to meeting crop nitrogen (N) demands. The BNF is, especially, important in low value crops (e.g., forages) and in developing economies. However, just like synthetic N fertilizers, BNF has issues of its own. Among the issues of great importance is the low and highly variable proportion of fixed N 2 transferred to non-N 2 -fixing plants. The proportion of transfer ranges from as low as 0% to as high as 70%, depending on a myriad of factors. Most of the factors (e.g., N fertilizer application, species, and cultivar selection) are management related and can, therefore, be controlled for improved N 2 fixation and transfer. In this chapter, we discuss current trends in BNF in selected legume crops, the global economics of BNF, and recent reports on N 2 transfer in agricultural production systems. Additionally, factors affecting N 2 transfer and management considerations for improving N 2 fixation and transfer are discussed.

Contribution, Utilization, and Improvement of Legumes-Driven Biological Nitrogen Fixation in Agricultural Systems

“…The transfer of biologically fixed nitrogen to neighboring and/or succeeding crop plants is highly variable and can range from as low as 0% to as high as 73%, depending on various factors (Islam and Adjesiwor, 2017), which can be the highest reported levels of 75-110 kg N ha −1 y −1 (Louarn et al, 2015). A common practice in agricultural systems for utilizing nutrient transfer from BNF is intercropping N 2 -fixing legumes with non-N 2 -fixing crops.…”

“…The degree of nitrogen transfer depends upon the quantity and concentration of legume N, microbial mineralization and immobilization in the rhizosphere, the availability of other N sources, and the degree of utilization by the associated crop (Peoples and Craswell, 1992;Thilakarathna et al, 2016;Islam and Adjesiwor, 2017). The amount of N available and the pathway of transfer are also seen to depend on the legume species (Wolfe and Cormack, 2002).…”

“…Part of the symbiotically fixed nitrogen in legumes is available to succeeding crops through the decomposition and mineralization of the legume residues (Thilakarathna et al, 2016;Islam and Adjesiwor, 2017). The residues of legumes can be a source of more mineral nitrogen to succeeding crops than the residues of cereal due to their relatively high nitrogen contents and relatively low C:N ratio in legume residue as compared with cereal residues.…”

“…The quantities of nitrogen fixed and the amount transferred to soil or subsequent plants in different agricultural systems as taken fromIslam and Adjesiwor (2017).…”

How can we possibly resolve the planet's nitrogen dilemma?

“…At present, biological nitrogen fixation provides some 200 million tons of nitrogen to our planetary ecosystems. In terms of agriculture, biological nitrogen fixation plays a modest role; it provides some 25% of all nitrogen needed by crop plants (Islam, 2017 ). Indeed, chemical fertilizers are thus far sufficiently inexpensive and a technologically programmable method for crop production.…”