The present study characterizes the floristic and phytosociological characters in the paraibano semiarid in Caatinga area. For the phytosociological survey 25, sample units with dimensions of 20 m x 20 m distributed randomly were used in order to collect the name of the species, the circumference at ground level (CFL), the circumference at breast height (CBH), the total height of the individuals and the state trees. The total surface of the area was 323.65 ha and 255.85 ha of shrub by arboreal vegetation what represent 79% of the area with vegetation, the remaining 21%, were classified as clean field, reservoirs, courses of water and highways, totaling 67.8 hectares. To the floristic composition 2.362 individuals were observed, which ones, 22 species belonged to 14 families. Considering the habit of the found species, 68% can be considered as arboreal and 32% as shrubby. The vegetation can be classified as a closed shrub-arboreal Caatinga. The most representative species and with the higher importance value (IV) in the area were Poincianella pyramidalis, Mimosa tenuiflora, Aspidosperma pyrifolium and Anadenanthera colubrina. The basal area average was 11.68 m²/ha. The species with higher basal area were P. pyramidalis, M. tenuiflora, A. colubrina and A. pyrifolium.
Aims: This study evaluated carbon assimilation, water relations, intrinsic and instantaneous water use efficiency, and water consumption of two cultivars of Ricinus communis L. cv. BRS 188 Paraguaçu and BRS Energia, subjected to regulated-deficit irrigation.
Study Design: The experiment was arranged in a completely randomized scheme in a factorial arrangement of 5 x 2, with five replicates.
Place and Duration of Study: The experiment was conducted in a greenhouse at the Universidade Estadual de Santa Cruz, Ilhéus, Brazil from December 2008 to February 2009.
Methodology: The growing plants were subjected to different water conditions by predefined quantities of water, so as to maintain the substrate under the following matric potential (Ψm) during the experimental period: -1.6 kPa (near field capacity), -3.0 kPa, -7.3 kPa, -26.7 kPa, and -183.0 kPa.
Results: The cultivars differed significantly (P = .05) in predawn leaf water potential and relative water content, showing that the tissues of BRS Energia remained more hydrated compared to
BRS 188 Paraguaçu. Under -183.0 kPa, the intrinsic water use efficiency and instantaneous water use efficiency were significantly higher in BRS Energia than in BRS 188 Paraguaçu, suggesting a conservative behavior of the cultivar BRS Energia. Non-stomatal limitations to photosynthesis were observed in BRS 188 Paraguaçu. Under greater water stress, BRS 188 Paraguaçu and BRS Energia plants had the leaf area reduced by 75.58% and 23.13%, respectively compared with the control. The water use efficiency of biomass was significantly higher in BRS Energia than in BRS 188 Paraguaçu.
Conclusion: The cultivar BRS Energia was more promising in relatively drier conditions compared to BRS 188 Paraguaçu. The carbon assimilation decreased in both castor bean cultivars only under severe water stress (-183.0 kPa), suggesting that the use of the deficit irrigation technique may be viable leading to lower water consumption and higher photosynthesis efficiency.
Management zones can be delimited using fuzzy logic, a technique that assigns values of degrees of pertinence to each pixel of a map. When the value tends to 1, these degrees indicate that there is certainty that the pixel belongs to a certain class of the management zone. However, in the boundary region between classes, degrees of pertinence do not tend to 1, indicating that there is confusion about which class such pixels belong. Depending on the area occupied by confused pixels, the use of management zones as a precision agriculture technique can be compromised. Thus, the behavior of the area occupied by pixels with different degrees of pertinence was evaluated as a function of the amount of information used to generate the management zones. Those zones were generated based on altitude, soil apparent electrical conductivity in soil depths of 0.20 m and 0.40 m, soil water content and clay content. When adding information to generate the management zones, there was an increase in the area occupied by pixels with degrees of pertinence lower than 0.5. However, the insertion of more than one layer of information to delineate the management zones improved the concordance between the management zones and the maps of the soil attributes. We suggest that some samples should be distributed in the border regions between the management zones, when these are delimited from the use of two or more variables.
Aims: In Madagascar, agroecological practices to increase and sustain upland rice productivity are based on an intensification of soil ecological processes.
Study Design: The effects of earthworm presence and identity (Pontoscolex corethrurus, Dichogaster saliens, or no earthworms), residue presence and identity [Crotalaria grahamiana (Fabaceae), Desmodium uncinatum (Fabaceae), Stylosanthes guianensis (Fabaceae), Eleusine coracana (Poaceae), Zea mays (Poaceae) or no residues] and residue location (mulched or buried) on nutrient availability and rice growth and yield were investigated in outdoor mesocosms. Thirty three treatments were managed in a completely random design.
Place and Duration of Study: The experiment was conducted at Andranomanelatra near Antsirabe, Vakinankaratra region, in the highlands of Madagascar in 2016.
Results: Earthworms had no effect on soil nutrient availability and positive effects on plant biomass. Nevertheless, the presence of earthworms increased the shoot:root ratio. The main significant effects on soil properties and crop yields were due to the presence, identity and location of the residues. The addition of Desmodium residues enhanced the total plant biomass, rice grain yields, soil nitrate content and total P uptake by rice. No significant interactive effect was found between earthworms and residues on plant and soil properties.
Conclusion: The most striking finding of the present study was that the identity and location of the residues were the most important factors influencing soil nutrient content, plant growth and crop production, irrespective of earthworm presence.
The SPR is an indicator that describes the physical strength that the soil exerts on the root that tries to move through along the profile, being directly influenced by bulk density, porosity and, mainly, by soil moisture at the time of evaluation. The soil resistance to penetration has been one of the most used parameters in the evaluation of its physical structure. The compaction is one of the problems of greatest relevance in different regions of Brazil, characterized by the alteration of the physical properties of the soil, being the direct result of a particular practice of management in which the soil is subjected to a pressure above its capacity to support, by encouraging the reduction of volume and resulting in increased resistance to penetration and in soil bulk density, impairing root growth and reducing the development of aerial part of the plants. To assist the management of these compacted areas, research has attempted to determine critical levels of soil physical properties for the proper development of the plants, using mainly the SPR. The penetrometer stands as the instrument capable of measuring and provide a good estimate of the soil penetration resistance by becoming an alternative to the survey information with respect to the soil physical quality in order to determine the appropriate management in the context of a sustainable conservation agriculture. In an attempt to resolve the problems arising from the increase of SPR, various alternatives may be used, such as the use of chisel plows and rippers, cover crop, especially species of aggressive root systems with high phytomass production among other management techniques. Knowing the critical limits of RMP is necessary in order to create a soil management plan that is viable and more sustainable for the agricultural system and that favors the growth of plants for productivity gains.