Journal
PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES
Volume 368, Issue 1619, Pages -Publisher
ROYAL SOC
DOI: 10.1098/rstb.2012.0154
Keywords
phosphorus fertilizer; phosphorus sorption; Amazon; soya bean agriculture
Categories
Funding
- NSF [DEB-0640661]
- Fundacao de Amparo a Pesquisa do Estado de Sao Paulo [FAPESP 03/13172-2]
- Watson Graduate Student Fellowship from MBL
- Center for Latin American and Caribbean Studies at Brown University
- Direct For Biological Sciences
- Emerging Frontiers [0949370] Funding Source: National Science Foundation
- Division Of Environmental Biology
- Direct For Biological Sciences [0949996] Funding Source: National Science Foundation
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Fertilizer-intensive soya bean agriculture has recently expanded in southeastern Amazonia, and whereas intensive fertilizer use in the temperate zone has led to widespread eutrophication of freshwater ecosystems, the effects in tropical systems are less well understood. We examined the fate of fertilizer phosphorus (P) by comparing P forms and budgets across a chronosequence of soya bean fields (converted to soya beans between 2003 and 2008) and forests on an 800 km(2) soya bean farm in Mato Grosso, Brazil. Soya bean fields were fertilized with 50 kg P ha(-1) yr(-1) (30 kg P ha(-1) yr(-1) above what is removed in crops). We used modified Hedley fractionation to quantify soil P pools and found increases in less-plant-available inorganic pools and decreases in organic pools in agricultural soils compared with forest. Fertilizer P did not move below 20 cm. Measurements of P sorption capacity suggest that while fertilizer inputs quench close to half of the sorption capacity of fast-reacting pools, most added P is bound in more slowly reacting pools. Our data suggest that this agricultural system currently has a low risk of P losses to waterways and that long time-scales are required to reach critical soil thresholds that would allow continued high yields with reduced fertilizer inputs.
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