Phosphorus Loss in Drainflow from Intensively Managed Grassland Soils

Abstract

The loss of P in subsurface drainage from lysimeters (0.5 ha), managed as either monoculture grass or grass‐clover for the last 9 yr have been quantified. Both systems received two to three cattle slurry applications annually and were cut two to three times before being grazed by dairy cattle. Mineral fertilizer‐P was applied only to the grass‐clover (about 25 kg P ha−1 yr−1). After 9 yr, NaHCO3‐soluble P in the topsoil (0–10 cm) averaged 38 and 47 mg P kg−1 for the grass and grass‐clover respectively, giving an average increase of 1.0 mg OIsen‐P kg−1 yr−1 in the grass‐clover. Drainage‐weighted molybdate‐reactive phosphorus (MRP) and total phosphorus (TP) concentrations ranged from 0.16 to 0.38 mg P L−1 and 0.45 to 0.79 mg P L−1, respectively during the 2‐yr study period. The MRP and TP losses in subsurface‐flow from the grass‐clover (1.68–2.03 and 3.47–5.03 kg P ha−1 yr−1, respectively) were significantly larger than those from the grass (1.27–1.34 and 2.97–3.58 kg P ha−1 yr−1, respectively). Averaged across years and pastures, MRP accounted for 42% of the TP loss, while a non‐MRP form accounted for 41% of the TP loss through field drains. Particulate‐associated P represented about 17% of the TP loss. The P losses in subsurface runoff measured in the present study were much larger than previous estimates. The results also showed that, despite the subsoil having much larger P‐sorption capacity than the topsoil, significant amounts of P losses could occur through preferential hydrological pathways.

Distributed hydrological modeling of total dissolved phosphorus transport in an agricultural landscape, part II: dissolved phosphorus transport

“…In particular, soils exhibiting preferential flow through macropores can quickly transport a significant amount of P to deeper soils Stamm et al, 1998;Gupta et al, 1999;Akhtar et al, 2003) and to subsurface drains (Hooda et al, 1999;Geohring et al, 2001). Baseflow chemistry has been shown to vary temporally and spatially with changes in land use, representing an integrated signal of climate, geology, and historical land use (Wayland et al, 2003).…”

Alterações no teor de fósforo no solo com aplicação de dejetos líquidos de suínos

“…A interação entre o O do fosfato e o cátion do grupo funcional, principalmente o aluminol dos argilominerais, e os grupos Fe-OH e Al-OH da superfície dos óxidos ocorre pelo compartilhamento eletrônico e, portanto, apresenta diferentes graus de energia de ligação (Barrow, 1983;Barrow et al, 1998;Barrow, 1999Barrow, ). et al, 1996Stamm et al, 1998;Hooda et al, 1999). O monitoramento dos teores de P biodisponível no solo pode auxiliar nas tomadas de decisão com relação às doses suportáveis ambientalmente, desde que se tenham valores referenciais, como em algumas regiões dos Estados Unidos (Sharpley & Halvorson, 1994).…”

The Potential of P Loss from Livestock Farms to Watercourses in Wensleydale; A Risk Mapping Approach

“…However, Hooda [49] demonstrated that limited slurry storage capacity and hence, slurry application during winter months is linked to high P concentrations in drainflow. In spite of this, it is discouraging that 90 of the farmers do not consider increasing the capacity to store manure.…”

“…This is strongly associated with the application rate of manure to soil in this time of year [49]. The role played by regulations is determinant in these results and in turn, makes difficult to understand the current policies.…”

“…Also important is the rise of the proportion of P in soluble form transported in this type of run-off. The presence of tracks, and overflows coming from these hardstandings result in shorter interactions between subsoil and runoff and hence, larger amounts of SRP reaching freshwaters [49]. In addition to this, it should be stressed that this type of management operations occur throughout the year and hence, SRP delivered to surface waters in spring/summer periods contributes to increasing the risk of rivers eutrophication [10].…”