Although the uses of plant growth stimulating bacteria (PGPR) to improve the yield of graminaceous crops have been studied for over seventy years the utility of the technology remains uncertain. Increases in crop yield have often been inconsistent, reflecting a lack of understanding of the mechanisms by which PGPR exert their effects. Because PGPR are able to fix N2, this was initially assumed to boost crops by supplementing soil N. However, it is now clear, that for most free living PGPR, other mechanisms affecting root development, and nutrient uptake can account for the observed increase in crop yields. Here we review the current state of our understanding of PGPR in graminaceous crop cultivation, identifying their potential contribution to more sustainable agricultural practices but also highlighting issues that need to be addressed before this technology can be appropriately assessed as a replacement for inorganic N addition.
Nitrogen fixing bacteria have been used for centuries to improve the fertility of agricultural soils. Since the introduction of inorganic nitrogen (N) fertiliser that provides a reliable boost to crop yields whilst reducing land and labour requirements, the use of biological nitrogen fixation has been in decline. Recently, concerns have been expressed about the sustainability of inorganic N fertiliser application, however, there remain doubts about whether N2 fixing bacteria alone can provide agriculture with sufficient fixed N to feed a burgeoning global population. In this paper we review the current state of our knowledge regarding those diazotrophic bacteria that have a role to play in agriculture. We focus on our current areas of research, particularly, the importance of understanding the classification and mechanism of action of N2 fixing bacteria that are used in agricultural soils. We discuss the applications of N2 fixing bacteria that illustrate their potential to provide sustainable N, particularly focussing on Australian and South American agricultural systems where these bacteria are widely exploited to maintain soil fertility. We also identify problems with the use of bacteria as inoculants, including ineffective inoculation due to poor quality preparation, the use of appropriate isolates and issues with sustainability. We review the outlook for biological N fixation highlighting how molecular biology may enable the expression of N fixation in non-leguminous crops.
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.