Soybean root growth and crop yield in reponse to liming at the beginning of a no-tillage system

Analyzing the soil near crop roots may reveal limitations to growth and yield even in a no-tillage system. The purpose of the present study was to relate the chemical and physical properties of soil under a no-tillage system to soybean root growth and plant yield after five years of use of different types of limestone and forms of application. A clayey Oxisol received application of dolomitic and calcitic limestones and their 1:1 combination in two forms: surface application, maintained on the soil surface; and incorporated, applied on the surface and incorporated mechanically. Soil physical properties (resistance to mechanical penetration, soil bulk density and soil aggregation), soil chemical properties (pH, exchangeable cations, H+Al, and cation exchange capacity) and plant parameters (root growth system, soybean grain yield, and oat dry matter production) were evaluated five years after setting up the experiment. Incorporation of lime neutralized exchangeable Al up to a depth of 20 cm without affecting the soil physical properties. The soybean root system reached depths of 40 cm or more with incorporated limestone, increasing grain yield an average of 31 % in relation to surface application, which limited the effect of lime up to a depth of 5 cm and root growth up to 20 cm. It was concluded that incorporation of limestone at the beginning of a no-tillage system ensures a favorable environment for root growth and soybean yield, while this intervention does not show long-term effects on soil physical properties under no-tillage. This suggests that there is resilience in the physical properties evaluated.

Growth and Nutrition of Eucalypt Rooted Cuttings Promoted by Ectomycorrhizal Fungi in Commercial Nurseries

ABSTRACT Ectomycorrhizal fungi (EMF) may improve the adaptation of eucalypts saplings to field conditions and allow more efficient fertilizer use. The effectiveness of EMF inoculum application in promoting fungal colonization, plant growth, nutrient uptake, and the quality of rooted cuttings was evaluated forEucalyptus urophylla under commercial nursery conditions. For inoculated treatments, fertilization of the sapling substrate was reduced by 50 %. The experiment was carried out in a completely randomized design in a 4 × 4 factorial arrangement, wherein the factors were inoculum application rates of 0 (control), 5, 10, and 15 gel beads of calcium alginate containing the vegetative mycelium of Amanita muscaria, Elaphomyces antracinus, Pisolithus microcarpus, andScleroderma areolatum, plus a non-inoculated treatment without fertilization reduction in the substrate (commercial). Ectomycorrhizal fungi increased plant growth and fungal colonization as well as N and K uptake evenly. The best plant growth and fungal colonization were observed for the highest application rate. The greatest growth and fungal colonization and contents of P, N, and K were observed at the 10-bead rate. Plant inoculation with Amanita muscaria, Elaphomyces anthracinus, and Scleroderma areolatum increased P concentrations and contents in a differential manner. The Dickson Quality Index was not affected by the type of fungi or by inoculum application rates. Eucalypt rooted cuttings inoculated with ectomycorrhizal fungi and under half the amount of commercial fertilization had P, N, and K concentrations and contents greater than or equal to those of commercial plants and have high enough quality to be transplanted after 90 days.

Physiological responses of two tropical weeds to shade: I. Growth and biomass allocation

Ipomoea asarifolia (Desr.) Roem. & Schultz (Convolvulaceae) and Stachytarpheta cayennensis (Rich) Vahl. (Verbenaceae), two weeds found in pastures and crop areas in Brazilian Amazonia, were grown in controlled environment cabinets under high (800-1000 µmol m-² s-¹) and low (200-350 µmol m-² s-¹) light regimes during a 40-day period. For both species leaf dry mass and leaf area per total plant dry mass, and leaf area per leaf dry mass were higher for low-light plants, whereas root mass per total plant dry mass was higher for high-light plants. High-light S. cayennensis allocated significantly more biomass to reproductive tissue than low-light plants, suggesting a probably lower ability of this species to maintain itself under shaded conditions. Relative growth rate (RGR) in I. asarifolia was initially higher for high-light grown plants and after 20 days started decreasing, becoming similar to low-light plants at the last two harvests (at 30 and 40 days). In S. cayennensis, RGR was also higher for high-light plants; however, this trend was not significant at the first and last harvest dates (10 and 40 days). These results are discussed in relation to their ecological and weed management implications.

Effect of management practices on mycorrhizal infection, growth and dry matter partitioning in field-grown bean

The experiment was carried out on unsterilized field soil with low phosphorus availability with the objective of examining the effect of cultural practices on mycorrhizal colonization and growth of common bean. The treatments were: three pre-crops (maize, wheat and fallow) followed by three soil management practices ("ploughing", mulching and bare fallow without "ploughing" during the winter months). After the cultural practices, Phaseolus vulgaris cv. Canadian Wonder was grown in this soil. Fallowing and soil disturbance reduced natural soil infectivity. Mycorrhizal infection of the bean roots occurred more rapidly in the recently cropped soil than in the fallow soil. Prior cropping with a strongly mycorrhizal plant (maize) increased infectivity even further.

Growth and yield of common bean cultivars at two soil phosphorus levels under biological nitrogen fixation

The genotypic differences on growth and yield of common bean (Phaseolus vulgaris L.) in response to P supply were evaluated in a field experiment under biological N2 fixation. Eight cultivars were grown at two levels of applied P (12 and 50 kg ha-1 of P -- P1 and P2 respectively), in randomized block design in factorial arrangement. Vegetative biomass was sampled at three ontogenetic stages. The effects of genotype and phosphorus were significant for most traits, but not the genotype ´ phosphorus interaction. The cultivars presented different patterns of biomass production and nutrient accumulation, particularly on root system. At P1, P accumulation persisted after the beginning of pod filling, and P translocation from roots to shoots was lower. The nodule senescence observed after flowering might have reduced N2 fixation during pod filling. The responses of vegetative growth to the higher P supply did not reflect with the same magnitude on yield, which increased only 6% at P2; hence the harvest index was lower at P2. The cultivars with highest yields also presented lower grain P concentrations. A sub-optimal supply of N could have limited the expression of the yield potential of cultivars, reducing the genotypic variability of responses to P levels.

Growth and biomass allocation of the C4 grasses Brachiaria brizantha and B. humidicola under shade

The growth and biomass allocation responses of the tropical forage grasses Brachiaria brizantha cv. Marandu and B. humidicola were compared for plants grown outdoors, in pots, in full sunlight and those shaded to 30% of full sunlight over a 30day period. The objective was to evaluate the acclimation capacity of these species to low light. Both species were able to quickly develop phenotypic adjustments in response to low light. Specific leaf area and leaf area ratio were higher for low-light plants during the entire experimental period. Low-light plants allocated significantly less biomass to root and more to leaf tissue than high-light plants. However, the biomass allocation pattern to culms was different for the two species under low light: it increased in B. brizantha, but decreased in B. humidicola, probably as a reflection of the growth habits of these species. Relative growth rate and tillering were higher in high-light plants. Leaf elongation rate was significantly increased on both species under low light; however, the difference between treatments was higher in B. brizantha. These results are discussed in relation to the pasture management implications.

Plant growth and phosphorus uptake in mycorrhizal rangpur lime seedlings under different levels of phosphorus

The objective of this work was to evaluate the response of rangpur lime (Citrus limonia) to arbuscular mycorrhiza (Glomus intraradices), under P levels ranging from low to excessive. Plants were grown in three levels of soluble P (25, 200 and 1,000 mg kg-1), either inoculated with Glomus intraradices or left noninoculated, evaluated at 30, 60, 90, 120 and 150 days after transplanting (DAT). Total dry weight, shoot P concentration and specific P uptake by roots increased in mycorrhizal plants with the doses of 25 and 200 mg kg-1 P at 90 DAT. With 1,000 mg kg-1 P, mycorrhizal plants had a transient growth depression at 90 and 120 DAT, and nonmycorrhizal effects on P uptake at any harvesting period. Root colonization and total external mycelium correlated positively with shoot P concentration and total dry weight at the two lowest P levels. Although the highest P level decreased root colonization, it did not affect total external mycelium to the same extent. As a result, a P availability imbalance affected negatively the mycorrhizal symbiosis and, consequently, the plant growth.

Potato plant growth and macronutrient uptake as affected by soil tillage and irrigation systems

The objective of this study was to evaluate potato plant growth and macronutrient uptake, as affected by soil tillage methods, in sprinkle and drip irrigated experiments. Eight treatments were set: T1, no tillage, except for furrowing before planting; T2, one subsoiling (SS); T3, twice rotary hoeing (RH); T4, one disc plowing (DP) + twice disc harrow leveling (DL); T5, 1DP + 2DL + 1RH; T6, 1DP + 2DL + 2RH; T7, 1SS + T6; T8, one moldboard plowing (MP) + 2DL. Treatments were arranged in a randomized block design with four replications. In both irrigation systems, plants presented higher emergence velocity index (EVI), when the soil was not tillaged, and the EVI was inversely related to the maximum tuber dry mass production. In both experiments, a functional direct relationship was found between the leaf area index and maximum tuber dry mass yield. The growth of plant organs (tuber, leaf, stem and root) and the macronutrient (N, P, K, Ca and Mg) contents in potato plant responded positively to a deeper soil revolving caused by plowing, especially with moldboard plow.

Closed soilless growing system for producing strawberry bare root transplants and runner tips

The objective of this work was to test a closed soilless growing system for producing bare root transplants and runner tips of two strawberry clones, using two categories of substrates. The system used corrugated roofing panels of fiber-cement, over which a substrate layer was used as a growing bed. The nutrient solution was pumped from a reservoir toward the upper end of the roofing panels and drained back to a reservoir. Plant growth and development were determined for two advanced strawberry clones, grown in sand or in Plantmax organic substrate. Growth of the stock plants and the number and dry mass of bare root transplants were similar in the substrates, but bare roots differed in their crown diameters by substrate. For number of runner tips, no significant differences were found in total, small, and medium categories in the substrates. A mean production of about 590 runner tips per square meter and 145 bare root transplants per square meter was obtained. For both clones, a large number of bare root transplants and runner tips of adequate size were produced in the closed soilless growing system using sand or organic substrate.

Simulation of soybean growth and yield under northeastern Amazon climatic conditions

The objective of this work was to parameterize, calibrate, and validate a new version of the soybean growth and yield model developed by Sinclair, under natural field conditions in northeastern Amazon. The meteorological data and the values of soybean growth and leaf area were obtained from an agrometeorological experiment carried out in Paragominas, PA, Brazil, from 2006 to 2009. The climatic conditions during the experiment were very distinct, with a slight reduction in rainfall in 2007, due to the El Niño phenomenon. There was a reduction in the leaf area index (LAI) and in biomass production during this year, which was reproduced by the model. The simulation of the LAI had root mean square error (RMSE) of 0.55 to 0.82 m² m-2, from 2006 to 2009. The simulation of soybean yield for independent data showed a RMSE of 198 kg ha-1, i.e., an overestimation of 3%. The model was calibrated and validated for Amazonian climatic conditions, and can contribute positively to the improvement of the simulations of the impacts of land use change in the Amazon region. The modified version of the Sinclair model is able to adequately simulate leaf area formation, total biomass, and soybean yield, under northeastern Amazon climatic conditions.

Assessment of growth and yield performance of rubber tree clones of the IAC 500 series

The objective of this work was to evaluate the performance of 15 clones of the IAC 500 series of Hevea brasiliensis, developed at Instituto Agronômico (IAC), over a 12-year period, in the northwest region of São Paulo State, Brazil. The 15 new clones evaluated are primary clones obtained from selected ortets within half-sib progenies. The clone RRIM 600, of Malaysian origin, was used as the control. Dry rubber yield performance over a four-year period, mean girth at the tenth year, girth increment before and during tapping, thermal properties of the natural rubber produced and other characters of the laticiferous system were evaluated. Forty percent of the clones were superior in comparison to the control for yield. Clone IAC 500 recorded the highest yield (66.81 g per tree per tapping) over four years of tapping, followed by IAC 502 (62.37 g per tree per tapping), whereas the control recorded 48.71 g per tree per tapping. All selected clones were vigorous in growth. The natural rubber from this IAC clones showed thermal stability up to 300ºC. No differences were observed in the thermal behavior of rubber among the IAC series and the RRIM 600 clones. The clones IAC 500, IAC 501, IAC 502, IAC 503 and IAC 506 are the more promising for small-scale plantations, due to growth and yield potential.

Growth and hematology of pacu subjected to sustained swimming and fed different protein levels

The objective of this work was to evaluate the effect of sustained swimming and dietary protein levels on growth and hematological responses of juvenile pacu (Piaractus mesopotamicus). A completely randomized design was used in a 3x2 factorial arrangement, with three levels of dietary protein (24, 28, and 32% crude protein), two rearing conditions (sustained swimming or motionless water), and 15 replicates. Fish were subjected to sustained swimming at the velocity of two body lengths per second (2 BL s-1), for 45 days. The level of dietary protein and the swimming conditions affected the performance, growth, and hematological profile of pacu. Swimming conditions influenced nutritional factors, increasing daily weight gain, specific growth rate, number of erythrocytes, mean corpuscular volume, and mean corpuscular hemoglobin. Fish under sustained swimming and fed with 24% crude protein showed better growth performance, with higher specific growth rate (4.11±0.88) and higher daily weight gain (2.19±0.47 g per day). Sustained swimming can increase the productive performance of pacu and simultaneously reduce dietary protein levels.

Growth and stress of dourado cultivated in cages at different stocking densities

The objective of this work was to evaluate the growth and the stress levels of juvenile dourado (Salminus brasiliensis) cultivated in cages. Fish stocked at densities of 15 (D15) and 30 (D30) fish per square meter were evaluated in a completely randomized design with three replicates. Fish were fed twice a day with extruded ration (42% crude protein). Density influenced only biomass and daily food intake, and glucose and lactate concentrations increased over time. D15 and D30 did not influence the growth of dourado. However, the increase of glucose and lactate levels over time indicates that cultivation in cages is a stressful condition for this species.

Plant growth and leaf-spot severity on eucalypt at different CO2concentrations in the air

The objective of this work was to evaluate the effects of increased air-CO2 concentration on plant growth and on leaf-spot caused by Cylindrocladium candelabrumin Eucalyptus urophylla. Seedlings were cultivated for 30 days at 451, 645, 904, and 1,147 µmol mol-1 CO2 ; then, they were inoculated with the pathogen and kept under the same conditions for seven days. Increased CO2concentration increased plant height and shoot dry matter mass, and decreased disease incidence and severity. Stem diameter was not affected by the treatments. Increased concentrations of atmospheric CO2 favorably affect eucalypt growth and reduce leaf-spot severity.

Growth and energy metabolism of Nile tilapia juveniles fed glycerol

The objective of this work was to evaluate the effect of inclusion of dietary glycerol in replacement to starch on the growth and energy metabolism of Nile tilapia juveniles. The experiment was carried out in a completely randomized design with four treatments (0, 5, 10, and 15% purified glycerol) and six replicates. Pelleted, isonitrogenous, and isocaloric diets were provided for 60 days. Growth performance parameters and muscle glucose and protein concentrations were not affected by dietary glycerol levels. The treatment with 15% glycerol presented higher levels of muscle and liver triglycerides. A quadratic effect of treatments on muscle and liver triglyceride concentrations was observed. The treatment with 0% glycerol presented higher hepatic glucose levels than the one with 15%. Treatments did not differ for concentrations of liver protein, as well as of plasma glucose, triglycerides, and protein. Treatments with 10 and 15% glycerol showed higher activity of the glucose-6-phosphate-dehydrogenase enzyme than the treatment with 5%; however, there were no significant differences in the hepatic activities of the malic and glycerol kinase enzymes. A linear positive effect of treatments was observed on the activity of the glycerol kinase enzyme in liver. Levels of glycerol inclusion above 10% in the diet of Nile tilapia juveniles characterize it as a lipogenic nutrient.