Spatial Variability of Soil Phosphorus in Relation to the Topographic Index and Critical Source Areas

Abstract

A measure of soil P status in agricultural soils is generally required for assisting with prediction of potential P loss from agricultural catchments and assessing risk for water quality. The objectives of this paper are twofold: (i) investigating the soil P status, distribution, and variability, both spatially and with soil depth, of two different first-order catchments; and (ii) determining variation in soil P concentration in relation to catchment topography (quantified as the "topographic index") and critical source areas (CSAs). The soil P measurements showed large spatial variability, not only between fields and land uses, but also within individual fields and in part was thought to be strongly influenced by areas where cattle tended to congregate and areas where manure was most commonly spread. Topographic index alone was not related to the distribution of soil P, and does not seem to provide an adequate indicator for CSAs in the study catchments. However, CSAs may be used in conjunction with soil P data for help in determining a more "effective" catchment soil P status. The difficulties in defining CSAs a priori, particularly for modeling and prediction purposes, however, suggest that other more "integrated" measures of catchment soil P status, such as baseflow P concentrations or streambed sediment P concentrations, might be more useful. Since observed soil P distribution is variable and is also difficult to relate to nationally available soil P data, any assessment of soil P status for determining risk of P loss is uncertain and problematic, given other catchment physicochemical characteristics and the sampling strategy employed.

Potential contributions of remote sensing to ecosystem service assessments

“…However, some authors note that these models may have limited generality (Thompson et al, 2006) or that unmeasured variables such as local management practices may be more important (Page et al, 2005). b Hydrological variables.…”

Spatial Variation of Soil Available Phosphorous in the Dal Lake Catchment of Lesser Himalayas

“…Robinson and Metternicht used three different techniques including Inverse Distance Weight (IDW), cokriging and spline methods for predicting the level of soil salinity, acidity and organic matter in South West of Australia and the results showed that the cokriging and spline methods were the best techniques for estimation of the soil salinity level and organic matter content. Results also showed that the IDW method was suitable for prediction of soil acidity level (Zare-Mehrjardi, 2010 and Dal Lake Catchment of Lesser Himalayas Robinson and Metternicht, 2006 Page et al (2005) investigated the soil P status, distribution, and variability, both spatially and with soil depth, of two different first-order catchments; and determined variation in soil P concentration in relation to catchment topography (quantified as the "topographic index") and critical source areas.…”

Real-Time Forecast of Hydrologically Sensitive Areas in the Salmon Creek Watershed, New York State, Using an Online Prediction Tool

“…Tools such as the New York State (NYS) Phosphorus (P) Runoff Index (P-Index) were developed, e.g., [4,18,28,32] that support planners in creating farm level nutrient management plans (NMPs) and the risk assessment of P export from agricultural fields to streams [33]. However, there still exists a gap between the scientific understanding of processes controlling NPS nutrient transport in watersheds dominated by VSA hydrology and the tools used by watershed planners to determine these high-risk areas [4,9,14,22,34].…”