Global assessment of limitation to symbiotic nitrogen fixation by phosphorus availability in terrestrial ecosystems using a meta‐analysis approach

Abstract

[1] Symbiotic nitrogen fixation (SNF) is the main natural source of nitrogen (N) in terrestrial ecosystems worldwide. Previous studies have shown that fixation of N by plants can be limited by the availability of phosphorus (P) in soils. We used global meta-analysis to investigate how P availability controls SNF. In experiments in which plants were grown in an artificial medium, severe P deficiencies in the nutritive solution ([PO 4 ] < 5-42 μM) depressed SNF flux through both a direct decrease in the plant fixation rate (i.e., decreased N fixed per unit of plant biomass) and an indirect effect (i.e., through plant biomass). In most experiments with plants grown in soils, SNF was proportional to plant biomass and was consequently only indirectly limited by P. Some cases using unfertilized and weathered soils (ultisols or oxisols), where plants were particularly P stressed, were an exception with both direct and indirect P limitations. Our global analysis of the P-SNF relationship indicated that P bioavailability commonly limited SNF flux. We conclude that the main driver of in situ P limitation is indirect via limitation of plant growth, except in certain cases where both indirect and direct constraints may play a role. These cases of severe P deficiency may be mainly found in weathered tropical soils of Africa and South America, probably in unfertilized croplands which are depleted in P due to repeated biomass harvests.Citation: Augusto, L., F. Delerue, A. Gallet-Budynek, and D. L. Achat (2013), Global assessment of limitation to symbiotic nitrogen fixation by phosphorus availability in terrestrial ecosystems using a meta-analysis approach, Global Biogeochem. Cycles, 27,[804][805][806][807][808][809][810][811][812][813][814][815]

Nutrient limitation of terrestrial free‐living nitrogen fixation

“…The lack of a strong relationship between N fixation rates and NPP runs counter to predictions of current global biogeochemical models used to forecast future carbon–nutrient–climate interactions. Our findings extend past evidence for nutrient limitation of symbiotic N fixation (Hungate et al ., ; Augusto et al ., ) and show widespread nutrient limitation of free‐living N fixation as well. Decoupling of N fixation rates from NPP may be particularly important in tropical forests, where free‐living N fixation is especially high and P limitation of N fixation becomes more pronounced under warmer and wetter conditions.…”

Investigating patterns of symbiotic nitrogen fixation during vegetation change from grassland to woodland using fine scale δ15Nmeasurements

“…The latter could result from increasing access to resources (such as phosphorus or soil moisture) that might limit fixation (Hartwig ; Augusto et al . ). At this site, available P in the rooting zone increases significantly with Prosopis age (Kantola ), and larger root systems increase access to soil moisture, shown to correlate with nodule abundance (Zitzer et al .…”

“…; Augusto et al . ), and variation in this system could be used to test hypotheses about long‐term controls over fixation during succession. Finally, Prosopis fixation rates may vary on seasonal time scales in response to pronounced changes in temperature and rainfall (Archer et al .…”

Impact of land management system on crop yields and soil fertility in Cameroon

“…Previous works had reported that OM application, whether incorporated or applied as mulch or as part of alley cropping, increased crop yields and with a positive interaction with lime, P, or K. Higher yields require more nitrogen, so it could be concluded that the system released more nitrogen to produce higher yields (Sudjadi et al, 1989). It was noted that in order to increase the levels of nitrogen or OM in the soils it was necessary to increase P reserves through fertilizer application (Sudjadi et al, 1989;Augusto et al, 2013). However, if nitrogen was the most important nutrient for crop growth and yield levels, it was also an element difficult to manage in fertilization.…”

“…So, it could be deduced that no-till farming techniques would need fertilizer supplements to express their productive potential. Combined with quantities of herbicide that required DS, as indicated by Barruiso et al (1994), this system would induce excessive use of chemical elements. This involved expenses and highlights the risks of environmental pollution (Thapa and Yila, 2012).…”