Search results for "Geta"

Seasonal variations of leaf area index of agricultural fields retrieved from Landsat data

2008

Abstract The derivation of leaf area index (LAI) from satellite optical data has been the subject of a large amount of work. In contrast, few papers have addressed the effective model inversion of high resolution satellite images for a complete series of data for the various crop species in a given region. The present study is focused on the assessment of a LAI model inversion approach applied to multitemporal optical data, over an agricultural region having various crop types with different crop calendars. Both the inversion approach and data sources are chosen because of their wide use. Crops in the study region (Barrax, Castilla–La Mancha, Spain) include: cereal, corn, alfalfa, sugar bee…

2021

Nitrogen (N) is one of the key nutrients supplied in agricultural production worldwide. Over-fertilization can have negative influences on the field and the regional level (e.g., agro-ecosystems). Remote sensing of the plant N of field crops presents a valuable tool for the monitoring of N flows in agro-ecosystems. Available data for validation of satellite-based remote sensing of N is scarce. Therefore, in this study, field spectrometer measurements were used to simulate data of the Sentinel-2 (S2) satellites developed for vegetation monitoring by the ESA. The prediction performance of normalized ratio indices (NRIs), random forest regression (RFR) and Gaussian processes regression (GPR) f…

Sentinel-1 & Sentinel-2 Data for Soil Tillage Change Detection

2018

In this paper, an algorithm using Sentinel-1 (S-1) and Sentinel-2 (S-2) data to identify changes of tillage over agricultural fields at approximately similar to 100m resolution is presented. The methodology implements a multiscale temporal change detection on S-1 VH backscatter in order to single out VH changes due to agricultural practices only. The algorithm can be applied over bare or scarcely vegetated agricultural fields, which are identified from S-2 NDVI measurements. An initial assessment at farm scale using in situ and S-1 and SPOT5-Take5 data, acquired over the Apulian Tavoliere in southern Italy in 2015, is illustrated. A full validation of the approach is in progress over three …

An agent-based model of a cutaneous leishmaniasis reservoir host, Meriones shawi

2021

International audience; Meriones shawi (M.shawi) is the main reservoir host for zoonotic cutaneous leishmaniasis (ZCL) in Central Tunisia. The incorporation of environmental and climatic effects on the spread of ZCL in M. shawi remains difficult. This study presents an agent-based model (ABM) to overcome these difficulties and examine the impact of environment (i.e. vegetation cover) and climate (i.e. temperature) on M. shawi movement and prevalence. The model simulation considers two agent types: rodent agent and field unit agent. We tested the model according to two types of rodent movement: random and thoughtful. We integrated time dependent normalized difference vegetation index (NDVI) …

The effect of substituted urea herbicides on the growth of excised tomato roots

1983

Summary The action of 23 herbictdal substituted ureas on the growth of excised tomato roots was studied in order to determine whether there is a link between the effects of these herbicides on oxidative phosphorylation and on the growth of non-photosynthetic tissues. Fourteen of these herbicides were inhibitory; chlortoluron and TBU were stimulatory but only in the light. Substituted ureas known to affect plant mitochondria inhibited root growth but to a lesser extent than some which had no action on mitochondria. No clear relationship was found between actions on mitochondria and on root growth. It is suggested that targets other than photosynthesis and oxidative phosphorylation exist for …

Behaviour of the herbicide EL-107 in wheat and rape grown under controlled conditions

1987

Summary The behaviour of 14C-EL-107 has been evaluated in winter wheat and rape, which are tolerant and susceptible, respectively, under field conditions. After 10- to 13-days’growth under controlled conditions, seedlings were allowed to absorb the herbicide through the roots. Two experiments were conducted to study the absorption and the metabolism of EL-107. Absorption was estimated during a 5-day treatment at the rate of 1–47 μM, and metabolism was studied after a 1-day treatment at 14.7 μM. The results showed that (i) rape plants absorbed more herbicide than wheat, and translocated less radioactivity into their shoots, and (ii) the metabolism of EL-107 proceeded actively only in the sho…

Seasonal evolution of the quality of fresh glasshouse tomatoes under Mediterranean conditions, as affected by air vapour pressure deficit and plant f…

2000

Abstract Changes in yield and quality of fresh tomatoes in response to air vapour pressure deficit (VPD) and plant fruit load were studied under Mediterranean summer conditions. Plants thinned to three or six fruits per truss were grown in two compartments, one at a VPD below 1.5 kPa, the other without VPD control. The seasonal trend in fruit yield and quality was assessed from April to September by weekly measurement of number, fresh weight and dry matter content of harvested fruits, together with the occurrence of blossom-end-rot (BER) and cracking. On two occasions, in July and September, sugar and acid content was measured at three ripening stages. The seasonal decrease in fresh yield w…

Managing arbuscular mycorrhizal fungi in cropping systems

2005

Market globalization, demographic pressure, and environmental degradation have led us to reconsider many of our current agricultural systems. The heavy use of chemical inputs, including fertilizers and pesticides, has resulted in pollution, decreased biodiversity in intensively-farmed regions, degradation of fragile agro-ecosystems, and prohibitive costs for many farmers. Low input sustainable cropping systems should replace conventional agriculture, but this requires a more comprehensive understanding of the biological interactions within agro-ecosystems. Mycorrhizal fungi appear to be the most important telluric organisms to consider. Mycorrhizae, which result from a symbiosis between th…

Soil feedback does not explain mowing effects on vegetation structure in a semi-natural grassland

2009

Due to its ability to create aboveground conditions that favour plant diversity, mowing is often used to preserve the high conservation value of semi-natural species-rich grasslands. However, mowing can also affect belowground conditions. By decreasing plant carbon supply to soil, mowing can suppress the activity of soil decomposers, diminish plant nutrient availability and thus create a feedback on plant growth. In this study, we first documented the effects of three-year mowing on plant community structure in a species-rich grassland. We found that mowing decreased the total areal cover of woody plants and increased the total cover of leguminous forbs. At the species level, mowing further…

Plant removal disturbance and replant mitigation effects on the abundance and diversity of low-arctic soil biota

2014

Abstract Due to the dependence of soil organisms on plant derived carbon, disturbances in plant cover are thought to be detrimental for the persistence of soil biota. In this work, we studied the disturbance effects of plant removal and soil mixing and the mitigation effects of replanting on soil biota in a low-arctic meadow ecosystem. We set up altogether six replicate blocks, each including three randomized treatment plots, at two distinct fells at Kilpisjarvi, northern Finland. Vegetation was removed in two thirds of the plots: one third was then kept barren (the plant-removal treatment), while the other third was replanted with a local herb Solidago virgaurea. The remaining plots of int…