The rate of swine wastewater application (SW) in agricultural production could result in the replacement of chemical fertilizers. However, SW destroys soil physical properties by decreasing pore bulk, which negatively affects both crop yield and development. In this context, this study aimed at monitoring the influence of swine wastewater as a cover fertilizer in maize and black oats in sequence on soil physical properties. Five application rates (0, 100, 200, 300 and 537 m3ha - 1 equivalent to 0, 11.2, 22.3, 33.5 and 60 kg ha-1 N, respectively, based on the average nitrogen concentration in SW) were tested with four replications each. In the studied area, soil porosity, density, and water content, before maize sowing and at the end of the cycles of maize and black oats, were determined by the volumetric ring method. Data were submitted for regression analyses. There was a reduction in the macroporosity and total porosity of the soil when the SW application rate, before maize cultivation, was higher. The introduction of black oats helped to improve the physical quality of the soil and reduced the compaction of the surface layer from 0 to 15 cm and 100 to 300 m3 ha-1 SW rates.

The objective of the present research is to characterize the phytotoxic activity of geopropolis from the Jandaira bee (Melipona subnitida Ducke) in the state of Ceará in Northeast Brazil and to analyze its effects. Extracts were prepared in 80% v/v grain alcohol at 0.25, 0.5, 0.75, and 1.0%. Their effects were determined on seed germination, radicle elongation, and hypocotyl growth of the pasture weeds malícia (Mimosa pudica) and mata-pasto (Senna obtusifolia). Extract phytotoxicity varied as functions of plant species, application dosage, and plant organ. M. pudica was more sensitive to the inhibitory effects of geopropolis than S. obtusifolia. There was a phytotoxic effect of 50% (PE50) for S. obtusifolia in terms of seed germination and in rootlet development near the maximum applied concentrations. M. pudica had PE50 and PE90 at the minimum concentration (0.25%) and near the maximum (1.00%), respectively. Thus, geopropolis extracts from the Jandaira bee (M. subnitida) are potentially phytotoxic to certain plant species.

The cowpea Vigna unguiculata (L.) Walp., also known as cowpea, is of fundamental socioeconomic importance to the northeast of Brazil, and has become one of the main sources of protein in the diet of the rural population. However, in this region, it has become necessary to identify genotypes that are better adapted to drought. In addition, research is needed regarding the action of substances that promote tolerance to stress factors. The aim of this study was to evaluate the antioxidative response of cowpea cultivars under osmotic stress conditions using potassium nitrate as an attenuator. Five osmotic potentials were tested in the substrate (0.0, −0.2, −0.4, −0.6, and −0.8 MPa), and three seed treatments (pre-soaking in distilled water, pre-soaking in potassium nitrate, and without pre-soaking) were tested in three cowpea cultivars (BRS Itaim, BRS Aracê, and BRS Potengi). The design was randomized with 45 treatments and four replications. The data were submitted to analysis of variance (P < 0.05), and in cases of significance, regression analysis was conducted to quantitate the factors. Our results indicate that an increase in proline content in cowpea plants may be seen as indicative of the intensity of water stress on germination and the initial stages of growth of the plant. The BRS Itaim cultivar best tolerates drought conditions with the application of potassium nitrate, given the increased activity of antioxidant enzymes such as superoxide dismutase, catalase, and ascorbate peroxidase.

The objective of this work was to technically and economically evaluate the productivity of tomato grown under different irrigation frequencies in the coast of Ceará, Brazil. The experiment was conducted in the experimental area of the Federal University of Ceará, Fortaleza, State of Ceará, Brazil, from August to December of 2011 and 2012. A randomized block experimental design was used in the two crop cycles, with six irrigation frequencies, consisted of 2 (F2), 3 (F3), 4 (F4), 5 (F5), 6 (F6) and 7 (F7) days of interval between irrigations, and four replications. The treatments were evaluated at twenty days after transplanting (DAT), when the plants were fully acclimated to the field. The harvesting began at seventy DAT and ended at ninety DAT. The variables analyzed were fruit length, diameter and weight, number of fruits per plant and fruit yield. The economic performance of the crop was also evaluated. Tomato producers of the coastal region of the State of Ceará, who aim to increase economic return, i.e., net income, must adopt a two- day irrigation frequency (F2).

The objective of this work was to assess the agronomic performance of cowpea cultivars depending on sowing seasons in the Cerrado biome. Thus, an experiment was conducted in Uberaba, State of Minas Gerais, Brazil, in a complete randomized block design, in a 6x3 factorial arrangement, using six cowpea cultivars ( BRS - Itaim , BRS - Guariba , BRS - Potengi, BRS - Cauamé , BRS - Novaera and BRS - Tumucumaque ) and three sowing seasons (Dec 14, 2012; Jan 14, 2013; and Feb 14, 2013), with four replications. The interaction between the cultivars and sowing seasons was assessed regarding the number of days for full flowering, number of days for pod maturation, number of trifoliate leaves, height of the first pod - bearing node, pod length, number of pods per plant, final plant population, 100 - grain weight and grain yield. The cowpea cultivars sown in December produced the lowest numbers of pods per plant and grains per pod, resulting in the lowest grain yields. The cultivar BRS - Tumucumaque had the highest grain yield in the January sowing. The highest grain yields were found in the February sowing, especially when the cultivars BRS - Itaim (3,439 kg ha - 1 ), BRS - Novaera (3,435 kg ha - 1 ), BRS - Guariba (3,168 kg ha - 1 ) and BRS - Potengi (3,107 kg ha - 1 ) was used.

The use of organic residues and compost is a common practice to improve soil quality and content of organic matter. In this study, the labile and stable fractions of soil organic matter were evaluated after application of layers of fresh (non-composted) or composted organic residues in a 6-year-old citrus orchard. The experiment was set up as a randomized block design, with 6 treatments: control without NPK, control with NPK, non-composted organic residue (NCOR, with and without NPK), and composted organic residue (humus, with and without NPK), with three replicates. The treatments were applied under the plant canopy. Soil samples were collected from the 0-0.05, 0.05-0.10, and 0.10-0.15 m layers. There were increases of 10.3, 22.4, 16.3, and 37.1 % in the organic carbon contents of the surface soil for the treatments using NCOR without NPK, NCOR with NPK, humus with NPK, and humus without NPK, respectively. The organic carbon contents of the labile fraction varied from 1.0 to 12.8 g kg-1, representing between 8 and 62 % of the total carbon. The carbon concentrations in the stable fraction varied from 3.1 to 9.7 g kg-1, representing between 38 and 92 % of the total carbon, and this was the dominant fraction for most of the treatments.

Information on the recovering of areas of gravel extraction of the Caatinga biome are scarce. Thus, the objective of this work was to assess the soil fauna as bioindicator of soil quality, evaluating areas with addition of topsoil (WAT) and control areas (CWT) without the addition of topsoil used for forest plantations, which were implemented for recovering gravel extraction areas. A native forest of the Caatinga biome (NFC) was taken as a reference. Ten traps with three replicates were installed in each area, which were evaluated in a randomized block design in split - plot arrangement at the end of the rainy season of different years, 0, 1, 3 and 6 years after the experiment implementation. A total of 45,740 specimens were captured. These specimens were from 36 taxonomic groups. The Acari, Diptera, Entomobryomorpha, Formicidae, Poduromorpha and Symphypleona were the predominant groups in all areas (WAT, CWT and NFC). Nine groups (25% of the total) had restricted occurrence. The fauna richness and diversity were higher in the NFC, followed by the WAT and CWT. The uniformity and total abundance of the soil fauna community showed no defined patterns. The abundance of most groups was inhibited in the treatments evaluated, compared with NFC, however, this adverse effect was more significant in CWT compared with WAT. The CWT and WAT had high similarity and both had very low similarity with NFC. The ecological complexity of soil fauna community was higher in NFC. The soil fauna was efficient as a bioindicator of soil quality, which was higher in WAT, compared with CWT.

The aim of this study was to evaluate physiological quality in seeds of sweet sorghum grown under semi-arid conditions, and to determine the age of physiological maturity of the seeds as a function of the foliar application of potassium silicate. The experiment was carried out at the Curu Valley Experimental Farm, in Pentecoste in the state of Ceará, during the rainy seasons of 2014 and 2015. The BRS 506 and BRS 511 varieties were used, under foliar fertilisation with potassium silicate at doses of 500, 1000 and 1500 mL.ha -1, in addition to the control lots (with no application); harvesting was at four periods, 30, 37, 44 and 51 days after full bloom (DAB). The percentage and speed of germination were evaluated, together with the accelerated ageing test and seedling growth. The seeds presented greater than 90% germination from 37 DAB, reaching high seedling vigour at 51 DAB. Foliar fertilisation with potassium silicate under the conditions of the experiment resulted in an increase in the physiological quality of the seeds. The BRS 506 and BRS 511 cultivars displayed the highest physiological quality between 49 and 53 DAF.

Nitrogen (N) is the second most important nutrient required by watermelons that can limit their growth and affect fruit quality when deficient. We evaluated the soil (N-nitrate) and foliar N contents and soluble-solid content of the watermelon 'Top Gun' in Brazil at six rates of N fertilization (0, 50, 100, 150, 200 and 250 kg ha-1). N-nitrate and foliar N levels increased linearly with rate. Number of total and marketable fruit, weight of total and marketable fruit and total and marketable yields varied quadratically with rate. N rates of 187 and 184 kg ha-1 produced the highest total and marketable yields, respectively. The rate of N fertilization did not significantly affect total-solid content.

In flood plains, cover crops are able to alter soil properties and significantly affect rice nutrition and yield. The aims of this study were to determine soil properties, plant nutrition, and yield of tropical rice cultivated on flood plains after cover crop cultivation with conventional tillage (CT) and no-tillage system (NTS) at low and high nitrogen (N) fertilization levels. The experimental design was a randomized block in a split-split-plot scheme with four replications. In the main plots were cover crops sunhemp (Crotalaria juncea and C. spectabilis), velvet bean (Mucuna aterrima), jackbean (Canavalia ensiformis), pigeon pea (Cajanus cajan), Japanese radish (Raphanus sativus), cowpea (Vigna unguiculata) and a fallow field. In the subplots were the tillage systems (CT or NTS). The nitrogen fertilization levels in the sub-subplots were (10 kg N ha-1 and 45 kg N ha-1). All cover crops except Japanese radish significantly increased mineral soil nitrogen and nitrate concentrations. Sunhemp, velvet bean, and cowpea significantly increased soil ammonium content. The NTS provides higher mineral nitrogen and ammonium content than that by CT. Overall, cover crops provided higher levels of nutrients to rice plants in NTS than in CT. Cover crops provide greater yield than fallow treatments. Rice yield was higher in NTS than in CT, and greater at a higher rather than lower nitrogen fertilization level.