Monitoring nitrogen nutrition in cotton

Both N excess and deficiency may affect cotton yield and quality. It would therefore be useful to base the N management fertilization on the monitoring of the nutritional status. This study investigated the correlations among the following determination methods of the N nutritional status of cotton (Gossypium hirsutum L., var. Latifolia): chlorophyll readings (SPAD-502®, Minolta), specific-ion nitrate meter (Nitrate Meter C-141, Horiba-Cardy®), and laboratory analysis (conventional foliar diagnosis). Samples were taken weekly from two weeks before flowering to the fifth week after the first flower. The experiment was conducted on the Fazenda Santa Tereza, Itapeva, State of São Paulo, Brazil. The crop was fertilized with 40 kg ha-1 N at planting and 0, 30, 60, 90, and 120 kg ha-1 of side-dressed N. The range of leaf N contents reported as adequate for samples taken 80-90 days after plant emergence (traditional foliar diagnosis) may be used as reference from the beginning of flowering when the plant is not stressed. Specific-ion nitrate meter readings can be used as a nutritional indicator of cotton nutrition from one week after pinhead until the third week of flowering. In this case, plants are well-nourished when readings exceed 8,000 mg L-1 NO3-. The chlorophyll meter can also be used to estimate the nutritional status of cotton from the third week of flowering. In this case the readings should be above 48 in well-nourished plants.

Chemical properties of soils treated with biological sludge from gelatin industry

The impact of agro-industrial organic wastes in the environment can be reduced when used in agriculture. From the standpoint of soil fertility, residue applications can increase the organic matter content and provide nutrients for plants. This study evaluated the effect of biological sludge from gelatin industry on the chemical properties of two Ultisols (loamy sand and sandy clay) and an Oxisol (clay). The experiment lasted 120 days and was carried out in laboratory in a completely randomized design with factorial arrangement, combining the three soils and six biological sludge rates (0, 100, 200, 300, 400, and 500 m³ ha-1), with three replications. Biological sludge rates of up to 500 m³ ha-1 decreased soil acidity and increased the effective cation exchange capacity (CEC) and N, Ca, Mg, and P availability, without exceeding the tolerance limit for Na. The increase in exchangeable base content, greater than the effective CEC, indicates that the major part of cations added by the sludge remains in solution and can be lost by leaching.

Comparison of the methane oxidation rate in four media

Landfill gas emissions are one of the main sources of anthropogenic methane (CH4), a major greenhouse gas. In this paper, an economically attractive alternative to minimize greenhouse gas emissions from municipal solid waste landfills was sought. This alternative consists in special biofilters as landfill covers with oxidative capacity in the presence of CH4. To improve the quality/cost ratio of the project, compost was chosen as one of the cover substrates and soil (Typic red yellow-silt-clay Podzolic) as the other. The performance of four substrates was studied in laboratory experiments: municipal solid waste (MSW) compost, soil, and two soil-compost at different proportions. This study aimed to evaluate the suitability and environmental compatibility as a means of CH4 oxidation in biofilters. Four biofilters were constructed in 60 cm PVC tubes with an internal diameter of 10 cm. Each filter contained 2.3 L of oxidizing substrate at the beginning of the experiment. The gas used was a mixture of CH4 and air introduced at the bottom of each biofilter, at a flow of 150 mL min-1, by a flow meter. One hundred days after the beginning of the experiment, the best biofilter was the MSW compost with an oxidation rate of 990 g m-3 day-1 , corresponding to an efficiency of 44 %. It can be concluded that the four substrates studied have satisfactory oxidative capacity, and the substrates can be used advantageously as cover substrate of MSW landfills.

Effect of rock powder and vinasse on two types of soils

Can vinasse accelerate the change of minerals in rock dust to obtain fertilizers, using residues from alcohol agro-industries and mining? Answering this question was the main objective of this study. Therefore, an experiment was set up in the laboratory in a completely randomized design using Polyvinyl Chloride (PVC) columns, in which the 0-50 cm layers of a clayey soil (eutroferric Red Oxisol) and sandy soil (Typic Quartzipsamment) were reproduced. We applied three different rates of basalt powder (0.0; 2.0, and 4.0 t ha-1) and one rate of vinasse (200 m³ ha-1) to the soils. The control was made by treatments with water (200 m³ ha-1) with the same rates of rock powder. Samples were first collected on the surface of each column (1, 15, 30, 45, 60, and 90 days after the application of vinasse and rock powder), and, at the end of the experiment, at the various depths and in leached water, to determine pH and the concentration of soluble Ca2+, Mg2+, and K+. There was a significant effect of the solvent and the soil on the surface layer, with higher concentrations found in the treatments with vinasse and in clayey soil, confirming the potential of vinasse to alter minerals in basalt powder. The resulting levels from the beginning to the end of the experiment suggest that sorption phenomena with neoformed mineral phases or organic acids may have occurred. It may be concluded that the use of rock powder and vinasse mixtures is a promising alternative for soil fertilization and recycling of waste from the sugarcane and mining industries.

MODELING OF SOIL LOAD-BEARING CAPACITY AS A FUNCTION OF SOIL MECHANICAL RESISTANCE TO PENETRATION

Estimation of soil load-bearing capacity from mathematical models that relate preconsolidation pressure (σp) to mechanical resistance to penetration (PR) and gravimetric soil water content (U) is important for defining strategies to prevent compaction of agricultural soils. Our objective was therefore to model the σp and compression index (CI) according to the PR (with an impact penetrometer in the field and a static penetrometer inserted at a constant rate in the laboratory) and U in a Rhodic Eutrudox. The experiment consisted of six treatments: no-tillage system (NT); NT with chiseling; and NT with additional compaction by combine traffic (passing 4, 8, 10, and 20 times). Soil bulk density, total porosity, PR (in field and laboratory measurements), U, σp, and CI values were determined in the 5.5-10.5 cm and 13.5-18.5 cm layers. Preconsolidation pressure (σp) and CI were modeled according to PR in different U. The σp increased and the CI decreased linearly with increases in the PR values. The correlations between σp and PR and PR and CI are influenced by U. From these correlations, the soil load-bearing capacity and compaction susceptibility can be estimated by PR readings evaluated in different U.

Boron Leaching Decreases withIncreases on Soil pH

ABSTRACT Management of boron fertilization depends on the magnitude of B leaching in the soil profile, which varies proportionally with the concentration of B in the soil solution, which, in turn, decreases as the soil pH increases due to the higher sorption of B on soil solid surfaces. The objective of this study was to quantify the effect of liming and rates of B applied to the soil on B leaching. The experiment was carried out in the laboratory in 2012, and treatments consisted of a factorial combination of two rates of liming (without and with lime to raise the soil pH to 6.0) and five rates of B (0, 10, 20, 50 and 100 mg kg-1, as boric acid). A Typic Rhodudalf was used, containing 790 g kg-1 clay and 23 g kg-1 organic matter; the pH(H2O) was 4.6. Experimental units were composed of PVC leaching columns (0.10 m in diameter) containing 1.42 kg of soil (dry base). Boron was manually mixed with the top 0.15 m of the soil. After that, every seven days for 15 weeks, 300 mL of distilled water were added to the top of each column. In the percolated solution, both the volume and concentration of B were measured. Leaching of B decreased with increased soil pH and, averaged across the B rates applied, was 58 % higher from unlimed (pH 4.6) than from limed (pH 6.6) samples as a result of the increase in B sorption with higher soil pH. In spite of its high vertical mobility, the residual effect of B was high in this oxisol, mainly in the limed samples where 80 % of B applied at the two highest rates remained in the soil, even after 15 water percolations. Total recovery of applied B, including leached B plus B extracted from the soil after all percolations, was less than 50 %, showing that not all sorbed B was quantified by the hot water extraction method.

Characterization of Ornamental Rock Residue and Potassium Liberation Via Organic Acid Application

ABSTRACT Organic acids present in organic matter and, or, exudates by microorganisms and plants can increase the liberation of potassium present in minerals. The objective of this study was to characterize the residue from ornamental rocks and evaluate the release of K from these residues after the application of organic acids. The experiment was conducted under laboratory conditions and followed a 2 × 3 × 5 factorial design with three replicates. The studied factors were: two organic acids (citric acid and malic acid), three ornamental rock residues (R1, R2 and R3) and five organic acid rates (0, 5, 10, 20 and 40 mmol L-1). After agitation, K concentrations were determined in the equilibrium solution. Successive extractions were performed (1, 5, 10, 15, 30 and 60 days after the start of the experiment). The organic acids used (citric and malic) promoted the release of up to 4.86 and 4.34 % of the total K contained in the residue, respectively, reinforcing the role of organic acids in the weathering of minerals and in providing K to the soil. The K quantities were, on average, 6.1 % higher when extracted with citric acid compared to malic acid.

Effect of arcelin protein on the biology of Zabrotes subfasciatus (Boheman 1833), in dry beans

Arcelin is a seed protein found in wild beans (Phaseolus vulgaris) which gives resistance to Mexican bean weevil, Zabrotes subfasciatus (Boheman 1833) (Coleoptera: Bruchidae). Studies were carried out with the objective of estimating the effect of four alleles of protein arcelin (Arc1, Arc2, Arc3 and Arc4) on the biology of Z. subfasciatus. The experiment was carried out in laboratory at Embrapa-Centro Nacional de Pesquisa de Arroz e Feijão, in Santo Antônio de Goiás, GO, Brazil, under non controlled conditions. The highest levels of antibiosis to Z. subfasciatus were observed in Arc1, with reduction in the number of eggs, number of emerged adults, adults longevity. In the line Arc2 only reduction in the number of emerged adults was observed. The lines Arc3 and Arc4 showed low efficiency on the reduction of progeny of Z. subfasciatus and effects in the longevity and egg-adult cycle were not detected. Insect sexual ratio was not altered by the presence of Arc1, Arc2, Arc3 and Arc4 in the seeds.

Phosphate solubilization and synergism between P-solubilizing and arbuscular mycorrhizal fungi

The objective of this work was to evaluate the ability of several P-solubilizing fungi to solubilize aluminum phosphate and Araxá apatite as well as the synergism between the P-solubilizing fungus, PSF 7, and arbuscular mycorrhizal fungi to promote clover growth amended with aluminum phosphate. Two experiments were carried out, the first under laboratory conditions and the second in a controlled environmental chamber. In the first experiment, PSF 7, PSF 9, PSF 21 and PSF 22 isolates plus control were incubated in liquid medium at 28ºC for eight days. On the 2nd, 4th and 8th day of incubation, pH and soluble P were determined. In the second experiment, clover was sowed in plastic pots containing 300 g of sterilized substrate amended with aluminum phosphate, 3 g L-1, in presence and absence of PSF 7 isolate and arbuscular mycorrhizal fungi. A completely randomized design, in factorial outline 2x2 (presence and absence of PSF 7 and arbuscular mycorrhizal fungi) and five replicates were used. In the first experiment, higher P content was detected in the medium containing aluminum phosphate. PSF 7 is the best fungi isolate which increases aluminum solubilization with major tolerance to Al3+. Clover growth was stimulated by presence of PSF 7 and arbuscular mycorrhizal fungi. There is synergism between microorganisms utilized to improve plant nutrition.

Impact of direct seeding mulch-based cropping systems on soil nematodes in a long-term experiment in Madagascar

The objective of this work was to assess the effects of conventional tillage and of different direct seeding mulch-based cropping systems (DMC) on soil nematofauna characteristics. The long-term field experiment was carried out in the highlands of Madagascar on an andic Dystrustept soil. Soil samples were taken once a year during three successive years (14 to 16 years after installation of the treatments) from a 0-5-cm soil layer of a conventional tillage system and of three kinds of DMC: direct seeding on mulch from rotation soybean-maize residues; direct seeding of maize-maize rotation on living mulch of silverleaf (Desmodium uncinatum); direct seeding of bean (Phaseolus vulgaris)-soybean rotation on living mulch of kikuyu grass (Pennisetum clandestinum). The samples were compared with samples from natural fallows. The soil nematofauna, characterized by the abundance of different trophic groups and indices (MI, maturity index; EI and SI, enrichment and structure indices), allowed the discrimination of the different cropping systems. The different DMC treatments had a more complex soil food web than the tillage treatment: SI and MI were significantly greater in DMC systems. Moreover, DMC with dead mulch had a lower density of free-living nematodes than DMC with living mulch, which suggested a lower microbial activity.

New experimental tools for bioassays with whitefly in laboratory

The objective of this work was to develop an experimental kit for assessments of repellency, deterrence for oviposition, and insecticidal activity on adults of the whitefly Bemisia tabaci biotype B. The kit, which consisted of arenas and nebulizer, was effective for conducting bioassays, and the application of aqueous extracts by inhaler was adequate. The techniques are simple, cheap, and may contribute to research on this insect.

Metabolic responses of guava trees irrigated withdifferent N and K levels in São Francisco Valley

The guava (Psidium guajava L.) cv. Paluma has been cultivated in São Francisco Valley, Northeastern of Brazil, for in natura consumption and processing purposes. In spite of its importance, there are few scientific knowledge regarding guava physiology, nutrition, irrigation and fertigation. The objective of this work was to evaluate the effect of weather conditions and different concentrations of N and K applied by fertigation in foliar contents of reducing sugars, total soluble sugars, starch, sucrose, amino acids, and proteins. The field experiment was carried out at Bebedouro Experimental Field and the biochemical evaluations at the Laboratory of Seed and Plant Physiology, both located at Embrapa Semi-Árido, Petrolina-PE. The doses of 200 g N and 100 g K2O; 400 g N and 200 g K2O; 600 g N and 300 g K2O; and 800 g N and 400 g K2O per plant were applied in an experiment field. The experimental design was totally randomized blocks, with four treatments and five blocks. The weather conditions influenced the plant photosynthesis, which affects the plants metabolism. Guava presented specific responses to N and K fertigation for each parameter evaluated. The weather conditions during the evaluation period influenced guava responses to N and K fertigation.

Production and quality of Anacardium othonianum Rizz. seedlings grown in different substrates

This study aimed to evaluate the effect of substrate on growth, emergence, nutrition, and quality of Anacardium othonianum Rizz. (cerrado cashew tree) seedlings. The experiment was conducted in a greenhouse at the Plant Tissue Culture Laboratory on the Rio Verde campus. The following substrates were used: 1) Bioplant®, 2) Mecplant® (MP) + carbonized rice husk (CRH) (7:3), 3) fine-grained vermiculite (FGV), 4) FGV+CRH (3:1), 5) FGV+CRH (1:1), 6) FGV+CRH (1:3), and 7) sugarcane bagasse (SB) + sugarcane mill filter cake (FC) (3:2). Emerged seedlings were counted at 2-day intervals for 38 days following emergence of the first seedling. At 39, 64, and 89 days after seeding (DAS), the following variables were measured: stem length (SL), stem diameter (SD), and number of leaves (NL). Accumulated dry weight, quality indices, and leaf macro- and micronutrient levels were determined at 89 DAS. Plants grown in the FGV and FGV+CFH (1:3) substrates had shorter stem lengths than the plants grown in other substrates. Increases in seedling growth were smaller between 64 and 89 DAS compared to the initial period of the experiment. The highest leaf N concentrations were found in the SB+FC substrate treatment group; P and K concentrations were higher for the MP+CRH (7:3), SB+FC, and Bioplant® treatments; and Ca levels were higher for the SB+FC and MP+CRH (7:3) substrate treatments. The MP+CRH (7:3) substrate treatment group had the highest leaf B and Mn micronutrient concentrations, and plants from the Bioplant® substrate group had the highest leaf B micronutrient content. Mg, S, Cu, Zn, and Fe concentrations did not differ among the different substrates. The plant traits that differed most among the treatments included stem length for the FGV and FGV+CRH (1:3) substrate groups and leaf nutrient concentrations, which were higher for the SB+FC group followed by the MP+CRH and Bioplant® treatments.

The use of mini-projects in an undergraduate laboratory course in chemistry

This paper reports the results of a three-year study of the effectiveness of mini-projects in a first year laboratory course in chemistry at a Scottish university. A mini-project is a short, practical problem which requires for its solution the application of the knowledge and skills developed in previously completed set experiments. A number of recommendations have been made about the most appropriate ways of introducing mini-projects into undergraduate laboratory course. The main hypothesis of this survey was concerned with the value of mini-projects in laboratory courses formulated within the context of Information Processing Theory.

Designing an undergraduate laboratory course in general chemistry

From an analysis of a learning model based on the theory of information processing four hypothesis were developed for improving the design of laboratory courses. Three of these hypotheses concerned specific procedures to minimise the load on students' working memories (or working spaces) and the fourth hypothesis was concerned with the value of mini-projects in enhancing meaningful learning of the knowledge and skills underpinning the set experiments. A three-year study of a first year undergraduate chemistry laboratory course at a Scottish university has been carried out to test these four hypotheses. This paper reports the results of the study relevant to the three hypotheses about the burden on students' working spaces. It was predicted from the learning model that the load on students working space should be reduced by appropriate changes to the written instructions and the laboratory organisation and by the introduction of prelab-work and prelab-training in laboratory techniques. It was concluded from research conducted over the three years period that all these hypothesised changes were effective both in reducing the load on students' working spaces and in improving their attitudes to the laboratory course.