Sarah Garré

Combining δ13C measurements and ERT imaging: improving our understanding of competition at the crop-soil-hedge interface

Background and aimsHedgerow cropping decreases erosion in hillside agriculture but also competes for water and nutrients with crops. This study combined two methods for an improved understanding of water and nutrient competition at the crop-soil-hedge interface.Methodsδ13C isotopic discrimination in plants and soil electrical resistivity tomography (ERT) imaging were used in a field trial with maize monocropping (MM) vs. leucaena hedgerow intercropping with and without fertilizer (MHF+ and MHF−) in Thailand.ResultsHedges significantly reduced maize grain yield and aboveground biomass in rows close to hedgerows. ERT revealed water depletion was stronger in MM than in MHF+ and MHF- confirming time domain reflectometry and leaf area data. In MHF+, water depletion was higher in maize rows close to the hedge compared to rows distant to hedges and maize grain δ13C was significantly less negative in rows close to hedges (-10.33‰) compared to distant ones (-10.64‰). Lack of N increased grain δ13C in MHF- (-9.32‰, p ≤ 0.001). Both methods were correlated with each other (r = 0.66, p ≤ 0.001). Combining ERT with grain δ13C and %N allowed identifying that maize growth close to hedges was limited by N and not by water supply.ConclusionCombining ERT imaging and 13C isotopic discrimination approaches improved the understanding of spatial-temporal patterns of competition at the hedge-soil-crop interface and allowed distinguishing between water and N competition in maize based hedgerow systems.

Estimating the parameters of a 3-D root distribution function from root observations with the trench profile method: case study with simulated and field-observed root data

Background and aimsRoot length density (RLD) is a parameter that is difficult to measure, but crucial to estimate water and nutrient uptake by plants. In this study a novel approach is presented to characterize the 3-D root length distribution by supplementing data of the 3-D distribution of root intersections with data of root length density from a limited number of soil cores.MethodsThe method was evaluated in a virtual experiment using the RootTyp model and a field experiment with cauliflower (Brassica oleracea L. botrytis) and leek (Allium porrum, L.).ResultsThe virtual experiment shows that total root length and root length distribution can be accurately estimated using the novel approach. Implementation of the method in a field experiment was successful for characterizing the growth of the root distribution with time both for cauliflower and leek. In contrast with the virtual experiment, total root length could not be estimated based upon root intersection measurements in the field.ConclusionsThe novel method of combining root intersection data with root length density data from core samples is a powerful tool to supply root water uptake models with root system information.

An Integrated Quantitative Method to Simultaneously Monitor Soil Erosion and Non-Point Source Pollution in an Intensive Agricultural Area

Abstract In China, some areas with intensive agricultural use are facing serious environmental problems caused by non-point source pollution (NPSP) as a consequence of soil erosion (SE). Until now, simultaneous monitoring of NPSP and SE is difficult due to the intertwined effects of crop type, topography and management in these areas. In this study, we developed a new integrated method to simultaneously monitor SE and NPSP in an intensive agricultural area (about 6 000 km 2 ) of Nanjing in eastern China, based on meteorological data, a geographic information system database and soil and water samples, and identified the main factors contributing to NPSP and SE by calculating the NPSP and SE loads in different sub-areas. The levels of soil total nitrogen (TN), total phosphorus (TP), available nitrogen (AN) and available phosphorus (AP) could be used to assess and predict the extent of NPSP and SE status in the study area. The most SE and NPSP loads occurred between April to August. The most seriously affected area in terms of SE and NPSP was the Jiangning District, implying that the effective management of SE and NPSP in this area should be considered as a priority. The sub-regions with higher vegetation coverage contributed to less SE and NPSP, confirming the conclusions of previous studies, namely that vegetation is an effective factor controlling SE and NPSP. Our quantitative method has both high precision and reliability for the simultaneous monitoring of SE and NPSP occurring in intensive agricultural areas.

Effects of a ‘one film for 2 years’ system on the grain yield, water use efficiency and cost-benefit balance in dryland spring maize (Zea mays L.) on the Loess Plateau, China

ABSTRACT ‘One film for 2 years’ (PM2) has been proposed as a practice to control the residual film pollution; however, its effects on grain-yield, water-use-efficiency and cost-benefit balance in dryland spring maize production have still not been systematically explored. In this study, we compared the performance of PM2 with the annual film replacement treatment (PM1) and no mulch treatment (CK) on the Loess Plateau in 2015–2016. Our results indicated the following: (1) PM2 was effective at improving the topsoil moisture (0–20 cm) at sowing time and at seedling stage, but there was no significant influence on soil water storage, seasonal average soil moisture or evapotranspiration; (2) PM2 induced significantly higher cumulative soil temperatures compared to CK, and there was no significant difference between PM2 and PM1; (3) no significant differences were identified in grain-yield and water-use-efficiency between PM1 and PM2, and compared to CK, they improved by 16.3% and 15.5%, respectively; (4) because of lower cost of plastic film, tillage, film laying and remove in PM2, economic profits improved by 21% and 70% compared to PM1 and CK. This research suggested that PM2 was effective at alleviating the spring drought and was beneficial in reducing poverty traps in dryland.

Impact of crop residue management on crop production and soil chemistry after seven years of crop rotation in temperate climate, loamy soils

Society is increasingly demanding a more sustainable management of agro-ecosystems in a context of climate change and an ever growing global population. The fate of crop residues is one of the important management aspects under debate, since it represents an unneglectable quantity of organic matter which can be kept in or removed from the agro-ecosystem. The topic of residue management is not new, but the need for global conclusion on the impact of crop residue management on the agro-ecosystem linked to local pedo-climatic conditions has become apparent with an increasing amount of studies showing a diversity of conclusions. This study specifically focusses on temperate climate and loamy soil using a seven-year data set. Between 2008 and 2016, we compared four contrasting residue management strategies differing in the amount of crop residues returned to the soil (incorporation vs. exportation of residues) and in the type of tillage (reduced tillage (10 cm depth) vs. conventional tillage (ploughing at 25 cm depth)) in a field experiment. We assessed the impact of the crop residue management on crop production (three crops—winter wheat, faba bean and maize—cultivated over six cropping seasons), soil organic carbon content, nitrate (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}

Ground-Based Soil Moisture Determination

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Three-Dimensional Electrical Resistivity Tomography to Monitor Root Zone Water Dynamics

\end{document}NO3−), phosphorus (P) and potassium (K) soil content and uptake by the crops. The main differences came primarily from the tillage practice and less from the restitution or removal of residues. All years and crops combined, conventional tillage resulted in a yield advantage of 3.4% as compared to reduced tillage, which can be partly explained by a lower germination rate observed under reduced tillage, especially during drier years. On average, only small differences were observed for total organic carbon (TOC) content of the soil, but reduced tillage resulted in a very clear stratification of TOC and also of P and K content as compared to conventional tillage. We observed no effect of residue management on the \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}

Comparison of heterogeneous transport processes observed with electrical resistivity tomography in two soils.

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The dual role of roads in the visual landscape: A case-study in the area around Mechelen (Belgium)

\end{document}NO3− content, since the effect of fertilization dominated the effect of residue management. To confirm the results and enhance early tendencies, we believe that the experiment should be followed up in the future to observe whether more consistent changes in the whole agro-ecosystem functioning are present on the long term when managing residues with contrasted strategies.

Noninvasive Monitoring of Soil Water Dynamics in Mixed Cropping Systems: A Case Study in Ratchaburi Province, Thailand

Soil water content is a key variable for understanding and modeling ecohydrological processes. In this chapter, we review the state of the art of ground-based methods to characterize the spatiotemporal dynamic of soil water content, from point to field scale. First, point measurements methods are briefly discussed. Then, field-scale hydrogeophysical approaches such as ground-penetrating radar, ground-based L-band radiometry, electromagnetic induction, electrical resistivity tomography, cosmic-ray neutron probes, global navigation satellite system reflectometry, and nuclear magnetic resonance are described in more details. The basic principles of the different techniques, the spatial and temporal characteristics of their measurements, their advantages and limitations, as well as the recent developments in the data processing are presented.