Showing papers by "Eduardo Fávero Caires published in 2016"

Liming in the conversion from degraded pastureland to a no-till cropping system in Southern Brazil

Abstract: A significant area in Brazil is covered with degraded pasturelands, which could be more appropriately used under no-till system. These soils are highly acid and physically fragile, and then there is a need to identify a better liming strategy that will improve the establishment of no-till systems. We hypothesized that the surface application of lime would be more efficient to alleviate soil acidity on degraded pastureland soils. A 4-year field trial examined the effect of a lime application (4.8 Mg ha −1 ) that had either been incorporated (0–20 cm) or surface-applied to an acid sandy loam Oxisol, originally under degraded pasture in Southern Brazil. Control treatments (no-lime) were applied with and without soil disturbance. A black oat ( Avena strigosa Schreb) – soybean ( Glycine max L. Merrill) cropping sequence was used for 4 years after no-till establishment. Soil chemical attributes, plant nutrient uptake, black oat dry biomass production and soybean grain yield were assessed. Soil acidity amelioration was achieved either by incorporating the lime or applying it onto the soil surface. Lime incorporation resulted in a faster neutralization reaction, whereas surface-applied lime provided longer lasting soil profile benefits. At 0–5 cm layer, both tillage treatments, especially with lime application, provided lower soil organic carbon levels than no-till treatments, with or without lime application, until the second year. These differences in soil organic carbon levels were not observed at the end of evaluation, after 4 years, probably because the residual tillage effect disappeared. Over time, the soil organic carbon levels at 5–10 cm layer were slightly increased or maintained close to the initial level, regardless of treatment. Overall, the plants responded to lime application, with an increase by 35% on soybean yield, regardless of the application method. Surface liming provided better economic returns than incorporated liming. Lime incorporation is not recommended in degraded lands due to the risks of SOC losses with soil disturbance and rapid pH increase. Despite of high soil acidity before no-till cultivation, the surface application of lime was the best alternative for alleviating soil acidity when establishing a no-till system on degraded pastureland.

Adubação nitrogenada em cobertura para o cultivo de milho com alto potencial produtivo em sistema de plantio direto de longa duração

Abstract: A intensificacao da producao para elevar a produtividade de milho tem aumentado a demanda por fertilizantes nitrogenados. Com o objetivo de avaliar a acidificacao do solo e definir as doses de maxima eficiencia tecnica (MET) e economica (MEE) de N-ureia em cobertura para obtencao de alta produtividade de milho, realizou-se um experimento no municipio de Candoi (PR), em um Latossolo Vermelho de textura argilosa sob plantio direto de longa duracao (30 anos). Os tratamentos, dispostos em blocos ao acaso com 4 repeticoes, constaram de 5 doses de nitrogenio (N), na forma de ureia: 0, 90, 180, 270 e 360 kg∙ha-1, aplicadas em cobertura no estadio de desenvolvimento V4. O milho, hibrido P1630, foi cultivado apos aveia-preta, em 2012, com 65 kg N∙ha-1 na semeadura. A aplicacao de N, na forma de ureia, reduziu o pHCaCl2, os teores de Ca2+ + Mg2+ trocaveis, a capacidade de troca de cations (CTC) efetiva e a saturacao por bases do solo. Os teores de N nas folhas e nos graos, a altura das plantas e da insercao da espiga, o numero de graos por fileira, a massa de graos por espiga, a massa de 1.000 graos e a exportacao de N pelos graos de milho aumentaram linearmente com as doses de N em cobertura. A produtividade de milho aumentou com as doses de N, de acordo com o modelo Linear Response Plateau. A MET e a MEE seriam obtidas com a dose de 209 kg N∙ha-1 em cobertura para produtividade de 19,6 t∙ha-1 de milho.

Use of active canopy sensors to discriminate wheat response to nitrogen fertilization under no-tillage

Abstract: Spectral reflectance sensors may be useful in discriminating biomass and nitrogen status in plants. A field experiment was carried out on a loamy Typic Hapludox under no-tillage in Ponta Grossa, Parana State, Brazil, aiming to evaluate the efficiency of active canopy sensors (GreenSeeker 505 and Crop Circle ACS-470) to discriminate wheat response to nitrogen fertilization by determining the dry mass, nitrogen status, and grain yield. A randomized complete block design was used and four treatments were replicated 12 times. The treatments consisted of nitrogen application, as urea, at the rates of 0, 50, 100, and 150 kg ha-1. The nitrogen rates were applied in topdressing at tillering of wheat crop. The readings from the sensors were sensitive to changes caused by nitrogen rates application and yet had close and significant correlations with the dry biomass production and nitrogen uptake by wheat plants. GreenSeeker 505 and Crop Circle ACS-470 sensors showed similar efficiency in discriminating biomass production and the nutritional status in the wheat crop related to nitrogen. Wheat grain yield was high and it did not follow the gains in the production of dry mass in the shoot.

Brazilian maize landraces: source of aluminum tolerance.

Abstract: The aim of this study was to prospect alleles for aluminum (Al) tolerance in different maize germplasms and to estimate the genetic parameters associated with that tolerance. Fifty-two hybrids from 4 seeds companies and 50 maize landraces were evaluated after 48 h of exposure to Al. The difference in root growth (DIF) was used to estimate the relative aluminum tolerance index (RATI). The results showed for both maize germplasms (hybrids or landraces) differences in root growth of genotypes when exposed to Al. The comparison between different germplasms clearly demonstrated the superiority of maize landraces for tolerance to Al in relation to hybrid genotypes were 17 of 50 landraces evaluated was classified as Al tolerant. Estimates of genetic parameters in both germplasms indicated, to this random sample of genotypes, the possibility of success for the development and selection of improved populations and an increase in the frequency of alleles for Al tolerance.

Adubação nitrogenada em cobertura para o cultivo de milho com alto potencial produtivo em sistema de plantio direto de longa duração Nitrogen fertilization in top dressing for corn crop with high yield potential under a long-term no-till system

Abstract: Agricultural intensification to increase corn yield has increased the demand for nitrogen fertilizers. A field experiment was carried out in Candoi, Parana State, Brazil, on a clayey T ypic Hapludox (Oxisol) under a long-term continuous no-till (30 years) to evaluate the effects of nitrogen (N) fertilization as urea in top dressing on soil acidification and determine the N-urea rates of maximum technical yield (MTY) and maximum economic yield (MEY) for obtaining high corn yield. A randomized complete block design was used, with four replications. The treatments consisted of N-urea application in top dressing at the rates of 0, 90, 180, 270, and 360 kg∙ha –1 . Urea was applied in the V4 stage of the crop corn. Corn, hybrid P1630, was cultivated after black oat in 2012, with 65 kg N∙ha –1 at sowing. The N application as urea decreased the soil pHCaCl 2 , the exchangeable Ca 2+ + Mg 2+ levels, the effective cation-exchange capacity (CEC) and the soil base saturation. The N content in leaves and grains, the plant and ear height, the number of grains per row, the mass of grains per ear, the 1,000-grain mass, and the N export by grain of corn increased linearly with increasing N rate applied in top dressing. Corn yield increased with N rates as the Linear Response Plateau model and stabilized at 19.6 t∙ha