Correção da sodicidade de dois solos irrigados em resposta à aplicação de gesso agrícola

The chemical and physical degradation of the soils by salinity and sodicity problems constitutes a serious obstacle in productive irrigated areas in arid and semi-add regions. In order to eval mate the effect of gypsum on electrical conductivity, pH, exchangeable sodium percentage, sodium, calcium and magnesium content in saturation extract and exchangeable sodium of two saline-sodic soils: one from irrigated Perimeter Engenheiro Arco Verde in the municipality of Condado and another from irrigated Perimeter of São Gonçalo, in the municipality of Sousa both in the Paraiba State Brazil, an experiment was carried out in green house of the Departamento de Solos e Engenharia Rural, Centro de Ciências Agrárias, Universidade Federal da Paraíba, Areia, Brazil, in a factorial design 2 × 5 referring the two soils and five gypsum levels equivalent to 0; 3.2; 6.3; 9.4 and 12.5 g kg-1 to each soil. The gypsum application exercised positive effects on reduction of salinity and sodicity. The values of electrical conductivity, exchangeable sodium percentage, pH and contents of soluble and exchangeable sodium in relation to data of the soils before application of treatments with gypsum in both the soils were found to decrease.

Root volume and dry matter of peanut plants as a function of soil bulk density and soil water stress

Soil compaction may be defined as the pressing of soil to make it denser. Soil compaction makes the soil denser, decreases permeability of gas and water exchange as well as alterations in thermal relations, and increases mechanical strength of the soil. Compacted soil can restrict normal root development. Simulations of the root restricting layers in a greenhouse are necessary to develop a mechanism to alleviate soil compaction problems in these soils. The selection of three distinct bulk densities based on the standard proctor test is also an important factor to determine which bulk density restricts the root layer. This experiment aimed to assess peanut (Arachis hypogea) root volume and root dry matter as a function of bulk density and water stress. Three levels of soil density (1.2, 1.4, and 1.6g cm-3), and two levels of the soil water content (70 and 90% of field capacity) were used. Treatments were arranged as completely randomized design, with four replications in a 3×2 factorial scheme. The result showed that peanut yield generally responded favorably to subsurface compaction in the presence of high mechanical impedance. This clearly indicates the ability of this root to penetrate the hardpan with less stress. Root volume was not affected by increase in soil bulk density and this mechanical impedance increased root volume when roots penetrated the barrier with less energy. Root growth below the compacted layer (hardpan), was impaired by the imposed barrier. This stress made it impossible for roots to grow well even in the presence of optimum soil water content. Generally soil water content of 70% field capacity (P<0.0001) enhanced greater root proliferation. Nonetheless, soil water content of 90% field capacity in some occasions proved better for root growth. Some of the discrepancies observed were that mechanical impedance is not a good indicator for measuring root growth restriction in greenhouse. Future research can be done using more levels of water to determine the lowest soil water level, which can inhibit plant growth.

Cotton root volume and root dry matter as function of high soil bulk density and soil water stress

Soil compaction reduces root growth, affecting the yield, especially in the Southern Coastal Plain of the USA. Simulations of the root restricting layers in greenhouses are necessary to develop mechanisms which alleviate soil compaction problems. The selection of three distinct bulk densities based on the Standard Proctor Test is also an important factor to determine which bulk density restricts root penetration. This experiment was conducted to evaluate cotton (Gossypium hirsutum L.) root volume and root dry matter as a function of soil bulk density and water stress. Three levels of soil density (1.2, 1.4, and 1.6 g cm-3), and two levels of water content (70 and 90% of field capacity) were used. A completely randomized design with four replicates in a 3×2 factorial pattern was used. The results showed that mechanical impedance affected root volume positively with soil bulk density of 1.2 and 1.6 g cm-3, enhancing root growth (P>0.0064). Soil water content reduced root growth as root and shoot growth was higher at 70% field capacity than that at 90% field capacity. Shoot growth was not affected by the increase in soil bulk density and this result suggests that soil bulk density is not a good indicator for measuring mechanical impedance in some soils.

Performance of cultivars of crisp mini-lettuce with respect to ground cover and spacing, in three planting times

The planting of lettuce in greenhouses, as well as covering beds with a polyethylene sheet, is a viable technology, promoting improvements in microclimatic conditions of the environment. In view of the little information on mini-lettuce, the aim of this work was to evaluate the performance of three cultivars of crisp minilettuce ('Green Frizzly', 'Red Frizzly no. 1' and 'Red Frizzly no. 2') with and without ground cover, under different spacings (20 × 15 cm and 20 × 20 cm), in three planting times (1: November 16, 2004; 2: December 17, 2004; and 3: January 20, 2005). The study was conducted in a greenhouse at UNESP-FCAV, Jaboticabal-SP. The experiments were carried out using a randomized block design, following a 3 × 2 × 2 factorial scheme with 12 treatments and three repetitions. The characteristics evaluated were plant height (cm), head diameter (cm), fresh weight (g) and number of leaves per plant. Planting time 3 was shown to be favorable for all the characteristics analyzed. 'Red Frizzly no. 2' was found to be the most suited to planting time 1, and for planting times 2 and 3, this cultivar did not differ from 'Red Frizzly no. 1'. The factor ground cover was not found to affect the characteristics evaluated, and therefore, cultivation without ground cover is recommended. The spacing 20 × 15 cm was shown to be favorable, resulting in cultivation with the highest populations, thereby increasing productivity. Based on the results obtained and for the conditions in which the experiment was conducted, it can be concluded that: planting time 3 (January 20, 2005) was the most favorable; the cultivars 'Red Frizzly no. 2' and 'Red Frizzly no. 1' are adapted to all the planting times; and cultivation without ground cover using a spacing of 20 × 15 cm was the most suitable.

Radiciações e frações solares UV, PAR, IV em estufa de polietileno: evolução anual média mensal diária e equações de estimativa

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Aspectos biológicos de Azya luteipes Mulsant, 1850 (Coleoptera: Coccinellidae) em Coccus viridis Grenn, 1889 (Hemiptera: Coccidae)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Sistemas de produção de mudas cítricas em viveiros protegidos no Estado de São Paulo

Pós-graduação em Agronomia (Horticultura) - FCA

Levantamento de nematoides fitoparasitas em áreas de produção de plantas ornamentais e reação de crisântemos aos nematoides das galhas

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Produção do tomateiro (Lycopersicon esculentum L.) cultivado em diferentes recipientes e níveis de cálcio na solução nutritiva

Pós-graduação em Agronomia - FEIS

Avaliação de recipientes com substrato de fibra de coco no cultivo de híbridos de melão rendilhado sob ambiente protegido

Pós-graduação em Agronomia - FEIS

Característica de recipiente e densidade de planta de pepino, cultivada em substrato de fibra de coco com fertirrigação

Pós-graduação em Agronomia - FEIS

Calibração de tanques evaporímetros de baixo custo sob diferentes diâmetros em ambiente protegido

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Características florais e dependência por polinizadores de cinco cultivares de pepino e manejo de colméias em estufas

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Cultivo e controle de insetos do tomateiro em diferentes ambientes

Pós-graduação em Agronomia - FEIS

Levantamento e manejo de nematoides fitoparasitas em áreas cultivadas com olerícolas na região Centro-Oeste do Estado de São Paulo

Pós-graduação em Agronomia (Proteção de Plantas) - FCA