Search results for "forest"
showing 10 items of 3780 documents
Dependence of seed nitrogen concentration on plant nitrogen availability during the seed filling in pea
1999
Abstract The final seed nitrogen (N) concentration of the pea ( Pisum sativum L.) varies greatly with environment. These variations seem to be related to N availability in the plant. To understand such an effect, the pattern of seed N concentration during seed filling was analysed at a given node as the ratio of seed N accumulation rate and seed dry matter accumulation rate. Three experiments were conducted in the field and glasshouse. Pea genotypes ‘Solara’, ‘Frisson’ and its non-nodulating mutant ‘P2’ were grown and different treatments were applied to manipulate N availability during seed filling. Treatments included N supply (addition of N fertiliser), depodding (removal of pods) and de…
: J. Sci. Food Agric.
2017
Background: The measurement of carbon isotopic discrimination in grape sugars at harvest (δ13 C) is an integrated assessment of water status during ripening. It is an efficient alternative to assess variability in the field and discriminate between management zones in precision viticulture, but further work is needed to completely understand the signal.; Results: This work, spanning over 3 years, performed in a hillslope toposequence in Burgundy, delineates the relationships between main soil properties (gravel amount, slope, texture) and the grapevine water status assessed by δ13 C. The highest δ13 C, indicating most severe water deficit, was recorded in gravelly soils on steep slopes. The…
Contamination of rapeseed harvest by volunteers of other varieties : a study of intergenotypic competition
2004
Rapeseed volunteers in rapeseed crops can cause contamination in harvest through pollen and seeds. The aim of the study was to predict pollen and seed production by volunteers in winter rapeseed crops according to the genotypes of the crop and the volunteers. Firstly an experimental analysis of intraspecific competition was carried out in 2000 and 2001 on two and six genotypes, respectively. The main competition period begins with vegetation onset and affects pollen and seed production of the volunteers. Relations between density, height, yield and number of flowers were developed based on results from experiments and literature. Knowing the densities and heights of volunteers and crop on t…
Assessing non-chemical weeding strategies through mechanistic modelling of blackgrass (Alopecurus myosuroides Huds.) dynamics
2010
; Because of environmental and health safety issues, it is necessary to develop strategies that do not rely on herbicides to manage weeds. Introducing temporary grassland into annual crop rotations and mechanical weeding are the two main features that are frequently used in integrated and organic cropping systems for this purpose. To evaluate the contribution of these two factors in interaction with other cropping system components and environmental conditions, the present study updated an existing biophysical model (i.e. AlomySys) that quantifies the effects of cropping system on weed dynamics. Based on previous experiments, new sub-models were built to describe the effects on plant survi…
Cropping system dynamics, climate variability, and seed losses among East African smallholder farmers: a retrospective survey.
2014
Abstract Climate variability directly affects traditional low input and rain-fed farming systems, but few studies have paid attention retrospectively to the cropping system’s ability to mitigate climate risk. This study analyzes the impacts of rainfall variability on farmers’ seed variety losses over time, considering changes in smallholder farming systems. The cropping system dynamics, in favoring maize at the expense of sorghum and pearl millet, have induced an increasing risk of seed loss during drought. Combining ecological anthropology and climatology, a retrospective survey asking farmers about the period 1961–2006 was carried out at three altitudinal levels (750, 950, and 1100 m) on …
Optimizing Hough transform for fertilizer spreading optical control
2006
International audience; In Europe, centrifugal spreading is a widely used method for agricultural soil fertilization. In this broadcasting method, fertilizer particles fall onto a spinning disk, are accelerated by a vane, and afterward are ejected into the field. To predict and control the spread pattern, a low-cost, embeddable technology adapted to farm implements must be developed. We focus on obtaining the velocity and the direction of fertilizer granules when they begin their flight by means of a simple imaging system. We first show that the outlet angle of the vane is a bounded value and that its measurement provides the outlet velocity of the particle. Consequently, a simple camera un…
[div]Long-term dynamics of the atrazine mineralization potential in surface and subsurface soil in an agricultural field as a response to atrazine ap…
2012
Abstract The dynamics of the atrazine mineralization potential in agricultural soil was studied in two soil layers (topsoil and at 35–45 cm depth) in a 3 years field trial to examine the long term response of atrazine mineralizing soil populations to atrazine application and intermittent periods without atrazine and the effect of manure treatment on those processes. In topsoil samples, 14 C-atrazine mineralization lag times decreased after atrazine application and increased with increasing time after atrazine application, suggesting that atrazine application resulted into the proliferation of atrazine mineralizing microbial populations which decayed when atrazine application stopped. Decay …
Microalgae community structure analysis based on 18S rDNA amplification from DNA extracted directly from soil as a potential soil bioindicator
2005
International audience; Soil algae are photosynthetically active microorganisms showing changeable community structure, depending on the soil type, the agricultural practices and the application of pesticides. To characterise algal community structure, molecular approaches complementary to classical microbiological approaches based on the isolation and the culture of soil algae are required. Our study describes a polymerase chain reaction (PCR) approach targeting algal 18S rDNA sequences of desoxyribonucleic acid (DNA) samples extracted either from unialgal eukaryotic microalgae culture, complex assemblages of microalgae populations or natural soil communities. Our first results showed that…
Enhanced isoproturon mineralisation in a clay silt loam agricultural soil
2005
International audience; 14C-ring-labelled isoproturon mineralisation was investigated in a French agricultural soil previously exposed to isoproturon. 50 different soil samples collected every 2 m along a transect of 100 m in length were treated one or two times with isoproturon under laboratory conditions and analysed by radiorespirometry. 94% of the soil samples showed a high ability to mineralise isoproturon with a relatively low variability in the cumulative percentage of mineralisation ranging from 30 to 51% of the initially added radioactivity for the samples treated once with the herbicide. About 45 to 67% of the initially added radioactivity was transformed into 14CO2 in soil sample…
Soil DNA evidence for altered microbial diversity after long-term application of municipal wastewater
2010
International audience; Water resources constitute a social, agricultural and economic problem in most countries of the southern Mediterranean Basin. Alternative strategies have been developed such as the reuse of municipal wastewater for irrigation in agriculture. Despite numerous advantages for soil fertility and crop productivity, recycling wastewater in soils also has several ecotoxicological and sanitary problems. Few investigations have assessed the risk by evaluating the impact of wastewater irrigation on soil microbes. Here, we report for the first time the short- and long-term effects of treated municipal wastewater irrigation on the density and genetic structure of bacterial and f…