Search

This review illuminates established knowledge of root–arbuscular mycorrhizal fungi (AMF)–plant mutualism to study the uptake of phosphorus (P) as a critical element for plant nutrition. We focus on P cycling, underscoring the role of AMF in enhancing P acquisition and plant resilience in the rhizosphere. The role(s) of plant roots, root exudates, and biomolecules in relevant soil processes is emphasized in this manuscript. Enhancing P uptake efficiency through AMF interaction presents a promising avenue for sustainable agriculture, with future research opportunities focusing on understanding underlying mechanisms and developing innovative technologies as a need to transition from the use of AMF as a biofertilizer or as an inoculation alternative for seeds to being an inspiration for the development of technology adapted to different crops. This is important to promote responsible agricultural practices and improve crop yields. We provide definitions of key terms and concepts for one of the best-known natural sustainable phosphorus systems. This manuscript illuminates and aims to inspire technology development to overcome the challenge of plant nutrition under P scarcity conditions. [ABSTRACT FROM AUTHOR]

Soil Organic Carbon (SOC) is a key indicator for understanding the carbon dynamics in agroecosystems. Carbon fractions, on the other hand, can be more sensitive over short periods and can detect changes in the distribution and relationship patterns of SOC pools. To test this hypothesis nine, 16-year-old agroforestry systems (AFS) were tested and compared with control at 0-15 cm and 15-30 cm soil depths for K2Cr2O7 oxidizable carbon (SOC), pH, Electrical Conductivity (EC), Microbial Biomass Carbon (MBC) and carbon fractions, viz. very labile (C1frac), labile (C2frac), less labile (C3frac), and non-labile (C4frac). Carbon lability index (CLI) and Stratification Ratio (SR) were calculated to assess the lability and vertical distribution of SOC. The study found that from the time of plantation, SOC stocks significantly improved in the range 19.82%-46.33% under different AFS with SOC sequestration ranging from 0.111 ± 0.002 to 0.697 ± 0.017 MgC ha-1 yr-1. Among different AFS, Bambusa vulgaris showed significantly higher SOC sequestration than all other treatments at both soil depths. AFS also demonstrated a significant improvement in SOC lability, leading to an increase in CLI by 0.08%-4.48% at 0-15 cm depth and a more pronounced improvement of 2.08%-18.32% at 15-30 cm depth. Among different AFS the highest improvement in CLI was observed in Bambusa vulgaris and the lowest in fallow land. The vertical distribution of carbon fractions in the soil was also affected by AFS, with the labile carbon fraction mostly concentrated in the topsoil layer as indicated by high SR values (1.133-1.203) for C1frac. The highly significant positive correlation (p < .05) of labile carbon fractions with SOC (r = .872** for C1frac, r = .900** for C2frac and r = .915** for C3frac) indicated the high dependence of SOC on labile carbon. The study revealed that AFS have the potential to significantly enhance carbon sequestration, while also impacting the lability and vertical distribution of SOC. [ABSTRACT FROM AUTHOR]

Cattle-based agriculture on sandy soils has generated concern over P leaching within the basin of Lake Okeechobee, Florida. Elevated P concentrations in surface and groundwater relate to P retention capacity of soils. To evaluate P release and storage capacity of impacted soils with fluctuating water tables, four intact soil cores were analyzed (one upland and three wetland) to determine their maximum sorption capacity ([S.sub.max]), equilibrium P concentration (EPC0), and soil P storage capacity (SPSC) up to 160-cm depth. Sorption isotherms were measured for samples at 10-cm depth increments and data fitted to a Langmuir model ([r.sup.2][greater than or equal to] 0.88). Both [EPC.sub.0] and water-soluble P were higher at the surface and decreased with depth. Oxalate-extractable Fe and Al correlated with (i) oxalate- extractable P ([r.sup.2] = 0.83), and (ii) [S.sub.max]([r.sup.2] = 0.71). In situ pore water concentrations collected using multisamplers were consistently higher than [EPC.sub.0] values. This discrepancy was much greater for near-surface horizons for which the difference may partially be due to redox-induced release of P previously scavenged by Fe under anaerobic (flooded) conditions. The SPSC values were positive, however, even when discounting Fe (i.e., assuming in situ chemical reduction) for samples from deeper horizons, suggesting that the small discrepancies for these horizons are not attributable to Fe oxidation. All cores had negative SPSC at the surface and high [EPC.sub.0], suggesting that neither wetland nor upland soils safely sequester additional P. High pore water P values in the surface horizons are consistent with the inference of the surface soils potentially being a source for P. doi: 10.2136/sssaj2010.0063