Influence of type and amount of straw cover on weed emergence

This research was undertaken during 2003-2004 growing season to evaluate the effects of type [forage sorghum hybrid Cober Exp (Sorghum bicolor x Sorghum sudanense), forage millet (Pennisetum americanum var. BN2), finger millet (Eleusine coracana), and St Lucia grass (Brachiaria brizantha)] and amount of straw cover (5.5 and 3.0 t ha(-1)) upon the emergence of Bidens pilosa, Chamaesyce spp., Amaranthus spp., and Commelina benghalensis, under field conditions of the Brazilian Cerrado, in the region of Uberlandia-MG. The control consisted additional treatment lacking the straw cover. Emergence of weed depended on the type and amount of straw cover, as well as the weed species. The lowest number of B. pilosa seedlings was found in the presence of forage sorghum straw; Chamaesyce spp. in the lack of straw; Amaranthus spp. in the presence of higher amount of forage sorghum and forage millet, and lower amounts of forage millet and Finger Millet. All the types and amounts of straw reduced the emergency of C. benghalensis, except at the lowest level of St Lucia grass and the lack of straw.

Performance of four tomato cultivars, with and without ground cover

The aim of the study was to evaluate the production of four tomato cultivars of determinate growth, in the field, with and without ground cover. The cultivars examined were: 'AP-533', 'AP-529', 'Hypeel 5131 and 'PS-41816', which were cultivated with a spacing of 1 m between rows and 0.4 m between plants. The experimental design utilized was that of subdivided parcels, where parcels were provided with and without a ground cover of black polyethylene, and subparcels consisted of the cultivars; eight repetitions were used. The eight central plants in the parcel were evaluated according to the following characteristics: fresh weight of fruit per plant and number of fruit per plant, separated by size. For the classification of fruit, the same plants were divided into classes based on the diameter of the fruit. The diameter size was as follows: class 1, 3 cm; class II, 4 cm; class III, 4.5 cm; and class IV, 5.5 cm. The results showed that there were no significant differences in production among the cultivars studied. Cultivars 'AP-533' and 'Hypeel 513' demonstrated greater production per plant, when ground cover was used, yielding 1474 and 1404 g/plant, respectively. When black polyethylene ground cover was not used, these cultivars produced 1258 and 1271 g of fruit per plant, respectively. The cultivars 'AP-529' and 'PS41818' showed a greater yield of fruit when cultivated without ground cover, with 1548 and 1663 g/plant, respectively. The cultivar 'Hypeel 513' had the highest percentage of fruit with the largest dimensions. An interaction was appeared between 'AP-529' and ground cover, where the production of this cultivar was lower with black polyethylene ground cover compared to bare ground. It is concluded that there are no significant differences in the cultivation of the tomato hybrids 'AP-533', 'Hypeel 513' and 'PS-41816' with and without ground cover, but that the cultivar 'AP-529' should be planted preferentially in soil without black polyethylene cover.

Physical quality of an Oxisol cultivated with maize submited to cover crops in the pre-cropping period

The intensive use of land alters the distribution of the pore size which imparts consequences on the soil physical quality. The Least Limiting Water Range (LLWR) allows for the visualization of the effects of management systems upon either the improvement or the degradation of the soil physical quality. The objective of this study was to evaluate the physical quality of a Red Latosol (Oxisol) submited to cover crops in the period prior to the maize crop in a no-tillage and conventional tillage system, using porosity, soil bulk density and the LLWR as attributes. The treatments were: conventional tillage (CT) and a no-tillage system with the following cover crops: sunn hemp (Crotalaria juncea L.) (NS), pearl millet (Pennisetum americanum (L.) Leeke) (NP) and lablab (Dolichos lablab L.) (NL). The experimental design was randomized blocks in subdivided plots with six replications, with the plots being constituted by the treatments and the subplots by the layers analyzed. The no-tillage systems showed higher total porosity and soil organic matter at the 0-0.5 m layer for the CT. The CT did not differ from the NL or NS in relation to macroporosity. The NP showed the greater porosity, while CT and NS presented lower soil bulk density. No <= 10 % airing porosity was found for the treatments evaluated, and value for water content where soil aeration is critical (theta(PA)) was found above estimated water content at field capacity (theta(FC)) for all densities. Critical soil bulk density was of 1.36 and 1.43 Mg m(-3) for NP and CT, respectively. The LLWR in the no-tillage systems was limited in the upper part by the theta(FC), and in the bottom part, by the water content from which soil resistance to penetration is limiting (theta(PR)). By means of LLWR it was observed that the soil presented good physical quality.

Nitrogen Supply for Cover Crops and Effects on Peanut Grown in Succession under a No-Till System

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Nitrogen washing from C3 and C4 cover grasses residues by rain

Crop species with the C-4 photosynthetic pathway are more efficient in assimilating N than C-3 plants, which results in different N amounts prone to be washed from its straw by rain water. Such differences may affect N recycling in agricultural systems where these species are grown as cover crops. In this experiment, phytomass production and N leaching from the straw of grasses with different photosynthetic pathways were studied in response to N application. Pearl millet (Pennisetum glaucum) and congo grass (Brachiaria ruziziensis) with the C-4 photosynthetic pathway, and black oat (Arena Strigosa) and triticale (X Triticosecale), with the C-3 photosynthetic pathway, were grown for 47 days. After determining dry matter yields and N and C contents, a 30 mm rainfall was simulated over 8 t ha(-1) of dry matter of each plant residue and the leached amounts of ammonium and nitrate were determined. C-4 grasses responded to higher fertilizer rates, whereas N contents in plant tissue were lower. The amount of N leached from C-4 grass residues was lower, probably because the C/N ratio is higher and N is more tightly bound to organic compounds. When planning a crop rotation system it is important to take into account the difference in N release of different plant residues which may affect N nutrition of the subsequent crop.

Soybean root growth and yield in rotation with cover crops under chiseling and no-till

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Cover crops and herbicide timing management on soybean yield under no-tillage system

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Ammonium and nitrate in soil and upland rice yield as affected by cover crops and their desiccation time

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Cotton development and yield according to nitrogen application and cover crops

Nitrogen application on the cover and the maintenance of straw, conducted by direct seeding, should meet the needs of agriculture and promote soil conservation. This study evaluates the effect of pre-sowing nitrogen application in cotton crops and cover crops by direct seeding, on the development and yield of cotton. It was conducted in the municipality of Selviria-MS during the agricultural years 2005/06, 2006/07 and 2007/08. The experimental design used was a randomized block design consisting of three cover crops (forage turnip, black oat and white oat) and four nitrogen doses (0, 30, 60 and 90 kg of N ha(-1)) in pre-sowing of cotton. In April 2006, April 2007 and April 2008, the assessments of plant development and also harvesting of the experimental plots of cotton cultivars were conducted. The results showed that after planting the cover crops, the yield and development and the heights of cotton plants increased with the use of pre-sowing N of 90 kg ha(-1), also showing that the forage turnip is a coverage plant that provides increased cotton.

Associations of Forest Cover, Fragment Area, and Connectivity with Neotropical Understory Bird Species Richness and Abundance

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Influence of forest cover and mesohabitat types on functional and taxonomic diversity of fish communities in Neotropical lowland streams

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

The omega DD vertex in a sum rule approach

The study of charmonium dissociation in heavy ion collisions is generally performed in the framework of effective Lagrangians with meson exchange. Some studies are also developed with the intention of calculate form factors and coupling constants related with charmed and light mesons. These quantifies are important in the evaluation of charmonium cross sections. In this Letter we present a calculation of the omega DD vertex that is a possible interaction vertex in some meson-exchange models spread in the literature. We used the standard method of QCD sum rules in order to obtain the vertex form factor as a function of the transferred momentum. Our results are compatible with the value of this vertex form factor (at zero momentum transfer) obtained in the vector-meson dominance model. (c) 2006 Elsevier B.V. All rights reserved.

Massive superstring vertex operator in D=10 superspace

Using the pure spinor formalism for the superstring, the vertex operator for the first massive states of the open superstring is constructed in a manifestly super-Poincare covariant manner. This vertex operator describes a massive spin-two multiplet in terms of ten-dimensional superfields.

Measurement of the t(t)over-bar production cross section in p(p)over-bar collisions at root s=1.96 TeV using secondary vertex b tagging

We report a new measurement of the t (t) over bar production cross section in p (beta) over bar collisions at a center-of-mass energy of 1.96 TeV using events with one charged lepton (electron or muon), missing transverse energy, and jets. Using 425 pb(-1) of data collected using the D0 detector at the Fermilab Tevatron Collider, and enhancing the t (t) over bar content of the sample by tagging b jets with a secondary vertex tagging algorithm, the t (t) over bar production cross section is measured to be sigma(p (t) over bar -> t (t) over bar +X)=6.6 +/- 0.9(stat+syst) +/- 0.4(lum) pb. This cross section is the most precise D0 measurement to date for t (t) over bar production and is in good agreement with standard model expectations.

Superstring vertex operators in an AdS(5) x S-5 background

A quantizable action has recently been proposed for the superstring in an AdS(5) x S-5 background with Ramond-Ramond flux. In this paper we construct physical vertex operators corresponding to on-shell fluctuations around the AdS(5) x S-5 background. The structure of these AdS(5) x S-5 vertex operators closely resembles the structure of the massless vertex operators in a flat background. (C) 2001 Elsevier B.V. B.V. All rights reserved.