Chapters authored
Nitrogen Fixation and Transfer in Agricultural Production Systems
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 (N2) 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 N2 transferred to non-N2-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 N2 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 N2 transfer in agricultural production systems. Additionally, factors affecting N2 transfer and management considerations for improving N2 fixation and transfer are discussed.
Part of the book: Nitrogen in Agriculture
Understanding Species Traits and Biodiversity Indices to Solve Problems Associated with Legume Persistence in Cropping Systems
Shading and competition for mineral nutrients by grass impair legume functions and production in mixed cropping systems. Sustained stress from competition and adverse environments contribute to shortened legume life spans in such cropping systems. This creates negative consequences to forage productivity. There are opportunities to solve the challenge of legume persistence by understanding species traits and plant community dynamics that foster coexistence and complementary resource use. Together with species’ unique ability to tolerate adverse soil factors such as water stress, acidity and salinity, self-seeding, and shade tolerance are positive traits among legume species that grow in mixed crops. In communities, converging leaf and shoot conformations as well as asynchrony in dry matter distribution among species can avert negative effects of species competition. While seeding ratios can influence forage production and quality, management including harvest frequency and optimizing phosphorus (P) and potassium (K) fertilizers have crucial roles in perpetuating legume growth and function in mixtures with grass. Some facts on species competition for light, water, and nutrient resources; shade avoidance; and biodiversity mechanisms are highlighted in this chapter.
Part of the book: Plant Competition in Cropping Systems