29 research outputs found
Maize grain yield response to changes in acid soil characteristics with yearly leguminous crop rotation, fallow, slash, burn and liming practices
Open Access JournalAn experiment was conducted for 4 years to assess the effectiveness of fallow, slash and burn farming systems on maize grain yield and soil chemical characteristics. It was also meant to measure the response to yearly rotation of maize and leguminous crops (cowpea and mucuna), as options for managing the acidity of the soil of the study site. The maize tolerant cultivar (cvr) out yielded the sensitive cvr and the farmers’ variety by 43% and 16% respectively. On the maize/grain legume rotation plots, the tolerant and sensitive cvr yielded 5% and 7% respectively more than their corresponding yields on plots with fallow, slash and burn rotation. Maize/grain legume rotation demonstrated one of the least soil acidifications, exhibiting the least increase in exchangeable Al (23%), H (24%), and Al saturation (5%) resulting in improved soil fertility through increase in available Ca (2%), Mg (85%), P (75%), and CEC (14%). The fallow, slash and burn rotation, associated with the tolerant cvr showed similar grain yield with grain legume rotation, but contributed more to soil acidification. Maize/leafy legume rotation gave a similar yield to the above mentioned practices. The yearly application of 250 kg ha-1 of dolomitic lime for four consecutive years did not result in significant changes in soil characteristics and grain yield especially for the Al tolerant cvr. However, application of 2250 kg ha-1 of lime neutralized the Al toxicity, regardless of the rotation scheme. The study concluded that the four years maize cultivation through fallow/ slash and burn rotation extensively used in the humid forest zone is not the best option on acid soil
Shaping speckles: spatio-temporal focussing of an ultrafast pulse through a multiply scattering medium
The multiple scattering of coherent light is a problem of both fundamental
and applied importance. In optics, phase conjugation allows spatial focussing
and imaging through a multiply scattering medium; however, temporal control is
nonetheless elusive, and multiple scattering remains a challenge for
femtosecond science. Here, we report on the spatially and temporally resolved
measurement of a speckle field produced by the propagation of an ultrafast
optical pulse through a thick strongly scattering medium. Using spectral pulse
shaping, we demonstrate the spatially localized temporal recompression of the
output speckle to the Fourier-limit duration, offering an optical analogue to
time-reversal experiments in the acoustic regime. This approach shows that a
multiply scattering medium can be put to profit for light manipulation at the
femtosecond scale, and has a diverse range of potential applications that
includes quantum control, biological imaging and photonics.Comment: 7 pages, 3 figures, published in Nature Communication
Modelling of the dynamics of AI and protons in the rhizosphere of maize cultivated in acid substrate
International audienc
The dynamics of protons, aluminium, and calcium in the rhizosphere of maize cultivated in tropicals acid soils: experimental study and modelling
34 ref.International audienc
Cation exchange on plant roots involving aluminium: Experimental data and modeling
International audienc
Influence of the matrix on analyte fragmentation in atmospheric pressure MALDI
In this paper, we report the measurement of the degree of analyte fragmentation in AP-MALDI as a function of the matrix and of the laser fluence. The analytes include p-OCH3-benzylpyridinium, three peptides containing the sequence EEPP (which cleave very efficiently at the E-P site), and three deoxynucleosides (dA, dG, and dC), which lose the neutral sugar to give the protonated base. We found that the matrix hardness/softness was consistent when comparing the analytes, with a consensus ranking from hardest to softest: CHCA >> DHB > SA approximate to THAP > ATT > HPA. However, the exact ranking can be fluence-dependent, for example between ATT and HPA. Our goal here was to provide the scientific community with a detailed dataset that can be used to compare with theoretical predictions. We tried to correlate the consensus ranking with different matrix properties: sublimation or decomposition temperature (determined using thermogravimetry), analyte initial velocity, and matrix proton affinity. The best correlation was found with the matrix proton affinity