Adriano Stephan Nascente

Cover crops and herbicide timing management on soybean yield under no-tillage system

The objective of this work was to evaluate the effect of cover crops and timing of pre-emergence herbicide applications on soybean yield under no-tillage system. The experiment consisted of four cover crops (Panicum maximum, Urochloa ruziziensis, U. brizantha, and pearl millet) and fallow, in addition to four herbicide timings (30, 20, 10, and 0 days before soybean sowing), under no-tillage system (NTS), and of two control treatments under conventional tillage system (CTS). The experimental design was a completely randomized block, in a split-plot arrangement, with three replicates. Soybean under fallow, P. maximum, U. ruziziensis, U. brizantha, and pearl millet in the NTS and soybean under U. brizantha in the CTS did not differ significantly regarding yield. Soybean under fallow in the CTS significantly reduced yield when compared to the other treatments. The amount of straw on soil surface did not significantly affect soybean yield. Chemical management of P. maximum and U. brizantha near the soybean sowing date causes significant damage in soybean yield. However, herbicide timing in fallow, U. ruziziensis, and pearl millet does not affect soybean yield.

Interferência das plantas daninhas na cultura do tomate para processamento

ABSTRACT Weed interference in processing tomato crops Weed control efficiency depends on the information about itsinterference on the crops. The interference of weed on tomato plantsof a processing variety, transplanted directly into the field wasevaluated. The field experiment was carried out, in a randomizedblock design with three replications, at Embrapa Hortalicas inBrasilia, Brazil. Plots were laid out with increasing periods of timein the presence or absence of weeds. In the first case, plots remainedunder weed interference from seedling stage until the followingperiods (days) of the tomato life cycle: 1-28, 1-35, 1-49, 1-63, 1-77and 1-91(whole cycle, harvest). After these periods the weeds grewfreely until harvesting time. In the second case, plots were weededfrom seedling stage until the previously described periods. After theseperiods weeds were removed by hand through the rest of the tomatocycle. Among 24 of the most frequent weed species, Bidens pilosa , Brachiaria plantaginea

Effects of row spacing and intercrop on maize grain yield and forage production of palisade grass

Abstract. Intercropping of maize (Zea mays L.) with perennial forage, such as palisade grass [Brachiaria brizantha (Hochst. ex A. Rich) Stapf], provides large amounts of biomass that can be used as straw for no-tillage systems or as pasture for animal grazing. In addition, the use of narrow row spacing may increase maize grain yield. However, it is important to evaluate intercrops at different row spacing to avoid reductions in both maize and forage biomass production. The objectives of this field experiment during two growing seasons in Brazil were as follows: (1) to evaluate the influence of intercropping and row spacing on maize yield, leaf nutrient concentration, and plant population and development; and (2) to assess the influence of row spacing on palisade grass herbage mass and leaf nutrient concentration. The experimental design was a randomised complete block design in a 2 × 2 factorial scheme, with eight replications. The treatments comprised two row spacing distances (0.45 and 0.90 m) and two crop management types (maize monoculture and intercropped with palisade grass). The nutrient concentrations in the leaves of the maize plants were in the ideal range for this crop under all conditions studied. Plant height, height of first ear, and number of grains per ear were higher with the narrow row spacing. Maize grain yield was similar in both crop management types (10 301 and 9745 kg ha–1 for monoculture maize and intercropped, respectively). However, maize grain yield at the narrow row spacing was higher than that obtained with the wide row spacing (9948 v. 8905 kg ha–1). In contrast, row spacing did not affect the nutrient level or quality (crude protein concentration) of palisade grass. The amount of dry matter (DM) from palisade grass was lower at maize harvesting (4.7 Mg ha–1) and 90 days after harvesting (6.9 Mg ha–1) under narrow spacing. However, the amount of DM was similar at both row spacings at 120 days after maize harvesting (9.2 Mg ha–1). When there is no problem with water and nutrient availability, the use of maize and palisade grass intercropping under both row spacing conditions (0.45 and 0.90 m) provides an option for the production of forage DM without reducing the maize grain yield.

Gas exchange rates, plant height, yield components, and productivity of upland rice as affected by plant regulators

The objective of this work was to evaluate gas exchange rates, plant height, yield components, and productivity of upland rice, as affected by type and application time of plant growth regulators. A randomized block design, in a 4x2 factorial arrangement, with four replicates was used. Treatments consisted of three growth regulators (mepiquat chloride, trinexapac-ethyl, and paclobutrazol), besides a control treatment applied at two different phenological stages: early tillering or panicle primordial differentiation. The experiment was performed under sprinkler‑irrigated field conditions. Net CO 2 assimilation, stomatal conductance, plant transpiration, and water‑use efficiency were measured four times in Primavera upland rice cultivar, between booting and milky grain phenophases. Gas exchange rates were neither influenced by growth regulators nor by application time. There was, however, interaction between these factors on the other variables. Application of trinexapac-ethyl at both tillering and differentiation stages reduced plant height and negatively affected yield components and rice productivity. However, paclobutrazol and mepiquat chloride applied at tillering, reduced plant height without affecting rice yield. Mepiquat chloride acted as a growth stimulator when applied at the differentiation stage, and significantly increased plant height, panicle number, and grain yield of upland rice. Index terms: Oryza sativa, net photosynthesis, stomatal conductance, transpiration, water‑use efficiency. Taxas de trocas gasosas, altura de planta, componentes de producao e produtividade de arroz de terras altas afetados por reguladores vegetais Resumo - O objetivo deste trabalho foi avaliar taxas de trocas gasosas, altura de plantas, componentes de producao e produtividade do arroz de terras altas, influenciados pelo tipo e pela epoca de aplicacao de reguladores de crescimento vegetal. O delineamento experimental foi utilizado em blocos ao acaso, em arranjo fatorial 4x2, com quatro repeticoes. Os tratamentos consistiram de tres reguladores vegetais (cloreto de mepiquat, trinexapac‑etil e paclobutrazol), alem de um tratamento controle, aplicados em dois estadios fenologicos: inicio do perfilhamento ou primordio da diferenciacao da panicula. O experimento foi conduzido em campo com irrigacao por aspersao. A assimilacao liquida de CO2, a condutância estomatica, a transpiracao e a eficiencia do uso da agua foram avaliadas na cultivar de sequeiro Primavera, por quatro vezes, entre os estagios de emborrachamento e de grao leitoso. As trocas gasosas nao foram influenciadas nem pelos reguladores, nem pelas epocas de aplicacao. Houve interacao entre os efeitos dos fatores sobre as demais variaveis. A aplicacao de trinexapac‑etil, tanto no perfilhamento como na diferenciacao, reduziu a altura de plantas e afetou negativamente os componentes de producao e a produtividade do arroz. No entanto, o paclobutrazol e o cloreto de mepiquat, aplicados no estagio de perfilhamento, reduziram a altura das plantas sem afetar a producao. O cloreto de mepiquat atuou como promotor de crescimento quando aplicado no estagio de diferenciacao de paniculas, e aumentou significativamente a altura das plantas, o numero de paniculas e a produtividade de graos. Termos para indexacao: Oryza sativa, fotossintese liquida, condutância estomatica, transpiracao, eficiencia de uso da agua.

Ammonium and nitrate in soil and upland rice yield as affected by cover crops and their desiccation time

The objective of this work was to evaluate the effect of cover crops and their desiccation times on upland rice yield and on the levels of nitrate and ammonium in a no-tillage soil. The experiment was carried out in a randomized blocks, with split plots and three replicates. Cover crops (plots) were sowed in the off-season (March 2009). In November 2009, at 30, 20, 10 and 0 days before rice sowing (split plots), herbicide was applied on the cover crops (fallow, Panicum maximum, Urochloa ruziziensis, U. brizantha and millet). Straw and soil were sampled (0 - 10 cm) at the sowing day, and after 7, 14, 21, 28 and 35 days. Straws from millet and fallow were degraded more rapidly and provided the lowest level of nitrate in the soil. Urochloa ruziziensis, U. brizantha and P. maximum produced higher amounts of dry matter, and provided the highest levels of nitrate in the soil. Millet provides the lowest nitrate/ammonium ratio and the highest upland rice yield. Desiccations carried out at 30 and 20 days before sowing had the largest levels of nitrate in the soil at the sowing date. Nitrogen content and forms in the soil are affected by cover crops and their desiccation times.

Produtividade de arroz de terras altas em função de reguladores de crescimento

Upland rice yield as a function of growth regulators The use of sprinkler-irrigation and/or high levels of fertilization in upland rice can increase plant height and hence plant lodging. Lodging can be controlled by using growth regulators, in order to reduce plant height. The objective of this study was to evaluate the efficiency of plant growth regulators applied at the stage of panicle primordium differentiation on the reduction of plant height and the impact on grain yield and its components of upland rice cultivar Primavera, under sprinkler irrigation. The experiment was arranged in a 3x4 factorial randomized blocks design with four replications. Treatments consisted of: mepiquat chloride and trinexapac-ethil applied at doses 9, 50, 100, and 200 mg a.i. ha-1, and paclobutrazol at doses of 0, 25, 50, and 100 mg a.i. ha-1. Plant growth regulators reduced rice plant height; increasing doses of regulators reduced upland rice grain yield and its components; trinexapac-ethyl was the most harmful to rice grain yield.In this study , it was not identified the dose of growth regulator that allied reduction in plant height and did not cause decrease in rice yield.

Análise de crescimento e produtividade de cultivares de arroz de terras altas dos tipos tradicional, intermediário e moderno

The growth analysis allows the characterization and understanding of the upland rice cultivars development. This study aimed at characterizing, by using the growth analysis, the physiological components and agronomic performance, as well as the differences among traditional, intermediate and modern upland rice cultivars. The experiment was conducted under upland rice conditions, favored by the use of supplementary irrigation. The experimental design was randomized blocks, with three treatments consisting of traditional (Caiapo), modern (Maravilha) and intermediate (BRS Primavera) cultivars and eight replications. The leaf area index (LAI), instantaneous growth rate (IGR), relative growth rate (RGR), net assimilation rate (NAR) and specific leaf area (SLA), as well as grain yield and yield components, were evaluated. The intermediate and traditional cultivars presented the highest total dry matter accumulation rate, while the traditional and modern ones showed the highest LAI. The intermediate cultivar presented the highest IGR, RGR, NAR and SLA levels, as well as the highest grain yield, as a consequence of the higher spikelet fertility and 1,000 grain mass.

Adubação de cultivares de feijoeiro comum em várzeas tropicais

The bean crop has a high economic and social importance for the Brazilian population. However, some aspects should be improved in its cropping system, such as the plants fertilization management. The common bean sub-irrigation, in the rice intercropping, has been a viable alternative for grain yield, in the lowland ecosystem. However, there are just a few studies on fertilization in tropical lowland conditions. Thus, this study aimed at evaluating the yield of common bean cultivars grown under tropical lowland conditions and sub-irrigation, in Lagoa da Confusao, Tocantins State, Brazil, in the winter of 2008, by using different fertilizers sources, doses and splittings. The experimental design was randomized blocks, in a factorial scheme (cultivars x forms of fertilization), with cultivars divided into groups (black, carioca and special). The common bean yield was higher with the early nitrogen fertilization, and even higher when it was combined with potassium in topdressing fertilization, being the Ouro Negro (black group), Pitoco (carioca group) and Cranberry and BRS Embaixador (special group) the cultivars that reached the highest grain yields. When the recommended fertilization was used, Ouro Negro (black group), Carioca (carioca group) and Jalo Precoce and BRS Embaixador (special group) reached the highest grain yield, for each grain group. Yield was higher for the black group cultivars, when compared to the carioca and special groups.

BRS Notável: a medium-early-maturing, disease-resistant Carioca common bean cultivar with high yield potential

BRS Notavel is a common bean cultivar with carioca grain, suitable for cultivation in 20 Brazilian states. It is a medium- early-maturing cultivar, with an average yield of 2,261 kg ha -1 , 8.5% higher than the controls, a high yield potential (4,472 kg ha -1 ),

Soil chemical properties affected by cover crops under no-tillage system

The use of cover crops in no-tillage systems (NTS) can significantly improve the soils fertility. Thus, a study was performed to evaluate changes in chemical properties of soil caused by cover crops in a no-tillage system. The field experiment consisted of the following crop rotation: cover crops/rice/cover crops/rice. The experimental design was in randomized blocks with three replications. Treatments consisted of four cover crops (Brachiaria brizantha(Hochst. ex A. Rich.) Stapf. cv. Marandu, Brachiaria ruziziensis R. Germ. and C.M. Evrard, Panicum maximum Jacq. cv. Coloniao, and Pennisetum glaucum(L.) R. Br. cv. BN-2) and fallow (control treatment). Soil samples were collected at the beginning of the summer crop in Oct 2007, Oct 2008 and Oct 2009 at 0-5 cm soil depth. The use of cover crops provided for a significant increase in the level of nutrients, soil organic matter, cation exchange capacity, and base saturation in the soil. Soil fertility improved from the first to second year with the growing of cover crops. The soil under cover crops P. glaucum, B. ruziziensis, and B. brizantha showed higher fertility than the area under fallow.