Impact of a conversion from cropland to grassland on C and N storage and related soil properties: Analysis of a 60-year chronosequence

https://doi.org/10.1016/j.geoderma.2006.03.033Get rights and content

Abstract:Land use change can lead to changes in a range of soil properties, including soil carbon (C) and nitrogen (N) content, bulk density and pH. Previous investigations on the effects of land use change have been biased towards the impact of forest clearing and afforestation in tropical environments. Therefore, the aim of this study is to determine the impact of a conversion from cropland to grassland on soil properties in two districts of the Lahn-Dill Highlands, Germany. We determined a land use history for the period 1945–2004 from aerial photographs and field surveys. This land use history was used to build a chronosequence of grassland sites with a different age since the conversion from cropland for both districts. Each chronosequence was sampled to determine bulk density, pH, coarse material fraction, C/N ratio and soil C and N content as a function of grassland age. Results showed that there was no clear dependency of soil properties on grassland age for both districts. It was concluded that observed differences within each district are much more related to differences in soil parent material or slope position, instead of land use. Interestingly, the reduction of the chronosequence analysis to a paired site survey led to an opposite conclusion for the Erda district because all investigated soil properties were significantly different for continuous grassland and cropland. This indicates that care is required when interpreting results from paired site surveys, especially when the equality of initial soil conditions is not (or cannot be) tested.

Agricultural conversion of floodplain ecosystems: Implications for groundwater quality ( Journal of Environmental Management Volume 153, 15 April 2015, Pages 74-83 )

Abstract: With current trends of converting grasslands to row crop agriculture in vulnerable areas, there is a critical need to evaluate the effects of land use on groundwater quality in large river floodplain systems. In this study, groundwater hydrology and nutrient dynamics associated with three land cover types (grassland, floodplain forest and cropland) were assessed at the Cedar River floodplain in southeastern Iowa. The cropland site consisted of newly-converted grassland, done specifically for our study. Our objectives were to evaluate spatial and temporal variations in groundwater hydrology and quality, and quantify changes in groundwater quality following land conversion from grassland to row crop in a floodplain. We installed five shallow and one deep monitoring wells in each of the three land cover types and recorded water levels and quality over a three year period. Crop rotations included soybeans in year 1, corn in year 2 and fallow with cover crops during year 3 due to river flooding. Water table levels behaved nearly identically among the sites but during the second and third years of our study, NO3–N concentrations in shallow floodplain groundwater beneath the cropped site increased from 0.5 mg/l to more than 25 mg/l (maximum of 70 mg/l). The increase in concentration was primarily associated with application of liquid N during June of the second year (corn rotation), although site flooding may have exacerbated NO3–N leaching. Geophysical investigation revealed differences in ground conductivity among the land cover sites that related significantly to variations in groundwater quality. Study results provide much-needed information on the effects of different land covers on floodplain groundwater and point to challenges ahead for meeting nutrient reduction goals if row crop land use expands into floodplains.

Most if not all research or study that presents daily loading has had concentration data, and combining with flow data to achieve daily loading figures. If you find studies with loading data that is specifically useful, contacting the author may help gain some concentration data. In many instances, concentration differences with be associated with streamflow rates, and stormwater responses add substantial energy for particles being dislodged and entrained into the landscape flow network, especially for larger and more intense events. The concentrations from this type conversion would depend on many factors, soils, slope, proximity to flow network, conservation practices (BMPs). But if you have daily loading and can obtain daily flow data, the conversion to a daily average concentration is possible, with the caveats that daily data may include substatial variabily, from day to day, and also within one day (eg, storms).

Hi Anoop Kumar Srivastava and William F. Hansen,

Thank you for the responses. I have developed a System Dynamics model that accounts for average TSS (mg/L) in four major river systems. Your comments have assisted me in making sure my consideration of sediment flux in river systems is adequate.

I found this article that relates TSS and land use change: Effects of Land-use Change on Nutrient Discharges from the

Patuxent River Watershed by Weller et al., 2003.