Milton Luiz de Almeida

Incremento na densidade de plantas: uma alternativa para aumentar o rendimento de grãos de milho em regiões de curta estação estival de crescimento

The development of earlier hybrids, with shorter plant height, lower leaf number and upright leaves has increased maize potential adaptability to withstand high plant densities. This trend may be emphasized on the high lands of Southern Brazil due to their mild Spring and Summer temperatures and shorter maize growing season. Four trials were carried out, aiming to investigate the viability of using higher than recommended plant populations, as an alternative to improve grain yield. The maize hybrids Cargill 901 and XL 370 were evaluated at several plant populations, ranging from 37000 to 100000pl ha-1, under different management situations. In three out of four experiments, plant populations above 60000pl ha-1 maximized grain yield. The greater competition among individuals verified at high plant populations did not decrease substantially the number of ears per plant, which contributed to improve maize adaptation to high plant densities. Therefore, for regions with a short growing season, the use of early small stature maize hybrids may be accompanied by an increment in plant population up to a value varying between 65000 and 80000pl ha-1. This is conceivable as long as there is adequate soil fertility, water availability and stem lodging resistant genotypes.^lpt^aO surgimento de novos cultivares de milho, de ciclo mais curto, estatura reduzida, menor numero de folhas e folhas mais eretas aumentou o potencial de resposta da cultura a densidade de plantas. Essa tendencia pode ser acentuada nos planaltos do Sul do Brasil, que apresentam temperatura media nos meses mais quentes inferiores a 22°C, o que resulta em menor estacao estival de crescimento. Quatro experimentos foram conduzidos objetivando avaliar a viabilidade de se trabalhar com densidade de plantas maiores do que as atualmente recomendadas para esta regiao, como uma forma de aumentar o rendimento de graos. Nestes experimentos, submeteram-se os hibridos Cargill 901 e XL 370 a uma populacao que variou de 37.000 a 100.000pl ha-1, sob diferentes situacoes de manejo. Em tres dos quatro experimentos realizados, o uso de densidade de plantas superior a 60.000plha-1 maximizou o rendimento de graos. A maior competicao intraespecifica verificada nas densidades mais elevadas nao reduziu drasticamente o numero de espigas por planta, o que contribuiu para a melhor adaptacao da cultura a densidades elevadas. Dessa forma, para locais com estacao estival de crescimento mais curta, o uso de cultivares precoces, de menor porte, pode ser acompanhado pelo incremento na densidade para valores compreendidos entre 65.000 e 80.000pl ha-1. Isso e possivel desde que se tenha bom nivel de fertilidade no solo, boa disponibilidade hidrica e cultivares resistentes ao acamamento.^len^aThe development of earlier hybrids, with shorter plant height, lower leaf number and upright leaves has increased maize potential adaptability to withstand high plant densities. This trend may be emphasized on the high lands of Southern Brazil due to their mild Spring and Summer temperatures and shorter maize growing season. Four trials were carried out, aiming to investigate the viability of using higher than recommended plant populations, as an alternative to improve grain yield. The maize hybrids Cargill 901 and XL 370 were evaluated at several plant populations, ranging from 37000 to 100000pl ha-1, under different management situations. In three out of four experiments, plant populations above 60000pl ha-1 maximized grain yield. The greater competition among individuals verified at high plant populations did not decrease substantially the number of ears per plant, which contributed to improve maize adaptation to high plant densities. Therefore, for regions with a short growing season, the use of early small stature maize hybrids may be accompanied by an increment in plant population up to a value varying between 65000 and 80000pl ha-1. This is conceivable as long as there is adequate soil fertility, water availability and stem lodging resistant genotypes.

Influência da redução do espaçamento entre linhas no rendimento do milho em regiões de verões curtos

(2) Abstract†n†The interest in reducing maize row spacing in the short growing season regions of Brazil is increasing due to potential advantages such as higher radiation use efficiency. This experiment was conducted to evaluate the effect of row spacing reduction on grain yield of different maize cultivars planted at different dates. The trial was conducted in Lages, in the State of Santa Catarina, Brazil, during 1996/97 and 1997/98 growing seasons, in a split-split plot design. Early (October†1 st ) and nor- mal (November†15) planting dates were tested in the main plot; two morphologically contrasting culti- vars (an early single-cross and a late double-cross hybrids) were evaluated in the split plots and three row widths (100, 75 and 50†cm) were studied in the split-split plots. The reduction of row spacing from 100 to 50†cm increased linearly maize grain yield. The yield edge provided by narrow rows was higher when maize was sown earlier in the season. Differences in hybrid cycle and plant architecture did not alter maize response to the reduction of row spacing.

A qualidade da luz afeta o afilhamento em plantas de trigo, quando cultivadas sob competição

O presente trabalho foi conduzido com o objetivo de verificar os efeitos da mudanca na qualidade da luz sobre a emissao de afilhos e na sua acumulacao de massa seca. A cultivar de trigo EMBRAPA 16 foi cultivada em comunidades de aproximadamente 400p- /m2, em condicoes naturais de radiacao durante o inverno, no Sul do Brasil. No primeiro experimento (baixa qualidade de luz), utilizaram-se filtros verde e vermelho entre as linhas, entre os estadios Haun de 1.0 a 3.1. No segundo experimento (melhor qualidade de luz), as plantas foram suplementadas durante o dia com luz vermelha (V) (660nm), entre os estadios Haun 1.0 e 3.1. Ja no terceiro experimento (baixa qualidade de luz), as plantas foram suplementadas durante o dia com luz vermelha extrema (Ve) (730nm), entre os estadios Haun 1.0 e 3.1. A qualidade da luz afetou a emissao de afilhos, sua massa seca e sua distribuicao entre o colmo principal e os afilhos. A baixa qualidade da luz (filtros verde e vermelho e luz Ve) induziu as plantas a emitir menos afilhos com menos massa seca/afilho. A baixa qualidade da luz priorizou o colmo principal sob condicoes de comunidades, antes que tivesse sido estabelecida a competicao pela quantidade total de luz recebida pelas plantas. A melhor qualidade de luz (luz V) teve efeito oposto. Os afilhos foram emitidos em maior numero e a alocacao de massa seca foi menos priorizada para o colmo principal do que nos tratamentos com baixa qualidade.

O afilhamento da aveia afetado pela qualidade da luz em plantas sob competição

Oat plants grown in communities can change their morphology at early stages of development because of differential light absorption on the red and far-red wavelengths. This was studied in open air experiments with oat cultivar UFRGS 15, sown from 300 to 350 plants/m2, under natural radiation conditions, in wintertime, in Southern Brazil. In the first experiment, blue filters were placed between plant rows in order to decrease light quality, between Haun stages 1.1 and 3.1. For second experiment, low fluence of red (660nm) e far-red (730nm) light were supplemented during the day to increase (red) and decrease (far-red) respectively the light quality. This was done between Haun stage 1.1 to 3.1, at two distances from the plants. In the third experiment, red and far-red light were also supplemented but for two different periods: emergence to Haun stage 2.1 and Haun stage 2.1 to 4.1. The blue filters and far-red supplementation (expts 1 and 2) induced plants to emit less tillers and tillers with less dry mass but was not seen in experiment 3, when soil chemical conditions were better than the other experiments. With red supplementation, plants emitted more tillers with more dry mass. Under these conditions, the mass ratio mainstem/tiller was less proeminent than under blue filters and far-red supplementation.

Análise de trilha dos componentes do rendimento de grãos em genótipos de canola

Grain yield is a variable of complex association which has an economic importance. A trial was conducted in Lages, SC, during the 1996-growing season, in order to determine the association and the direct and indirect effects of some agronomic traits on grain yield of 12 canola genotypes, through the study of the phenotypic correlation and path analysis. A randomized complete block design with four replications per treatment was used. According to the analyses performed on the trial, plant height didn’t show any association with weight of 1,000 grains and grain yield. Path analysis showed that the primary components plant population per area and number of grains per plant have the largest direct impact on grain yield. On the other hand, the number of grains produced per plant is the major responsible for the increase in the weight of 1,000 grains. Path analysis also evidenced that the secondary component number of grains per pod has the highest direct effect on grain yield.

Conceito de ideotipo e seu uso no aumento do rendimento potencial de cereais

This review has the purpose of presenting some important traits to be incorporated in cereals through the integration of physiology, biochemistry and plant breeding. Several plant attributes were modified during the selection process to improve grain yield of different plant species. This paper intends to discuss the validity of aggregating some of the se traits in new cultivars and to pinpoint the possible consequences of using those individual characteristics rather than grain yield per se to bred the old genotypes. Discussion about crop ideotipes grows in importance with the fast evolution of genetic variability techniques because if a model plant to increase grain yield is not defined all the new genetic technology available may have a narrow practical utilization. This ideotipe was formulated integrating severa! characteristics that have been analyzed individually in the past. Its main proposed features are: (a) higher initial growth and greater communal phytomass, which are both important to improve solar radiation use, particularly during early stages of development, (b) an increase in photosynthetic capacity through the enhancement of sink strength with a probable effect on harvest index. The collective influence of the suggested traits must be evaluated on different genotypes to analyze the response level obtained.

Desempenho de híbridos de milho com ciclos contrastantes em função da desfolha e da população de plantas

The speed of maize development from emergence to anthesis may affect the response of the crop to important management practices and interfere on the ability of corn to cope with stresses at flowering. This experiment was conducted objecting to evaluate the relationship between earliness and maize response to the increase in plant population and defoliation. The trial was performed in Lages, SC, Brazil, during 1999/2000. Three contrasting hybrids in terms of heat unit requirement to reach flowering were tested: P32R21, very early; Premium, early; and C333B, late. These hybrids were submitted to four plant populations: 25,000, 50,000, 75,000 and 100,000 pl ha-1. Genotypes were evaluated with full leaf area and removing half of their green leaves at silking. The plant population required to maximize grain yield was lower for late than for early hybrids. Hybrid P32R21 presented a smaller leaf area and greater grain yield than C333B, regardless of defoliation. This was accomplished due to P32R21 higher capacity to mobilize its stem stored compounds to match the sink demand of the grain.

Crescimento inicial de milho e sua relação com o rendimento de grãos

This study was conducted aiming to identify morphological and physiological traits associated with the initial growth speed and to determine the importance of a vigorous early growth to set high grain yields. The study was conducted in Lages, SC, during 1998/99 and 1999/00 growing seasons. A randomized complete block design was used. Hybrids C901, AS 3601, C 505, AS 3466 and AS 32 were avaluated in 1998/99, whereas in 1999/00 the studied hybrids were C 909, AS 3601, DINA 500, AS 3466 and AS 32. Maize initial growth was evaluated through six samplings. Samples were taken weekly from plant emergence the ten fully expanded leaves stage. Leaf area, leaf area index, dry mass accumulation, cellular growth rate (CGR) and cellular expansion rate (CER) were estimated. Hybrid AS 3601 presented larger values of leaf area, IAF and CER than the other genotypes in 1998/99. In the second growing season, Hybrid AS 3466 had the highest values for dry mass and CGR. There was no significant difference among hybrids for grain yield. Low correlation values between initial growth parameters and maize grain yield were found. Otherwise, leaf area, leaf area index, dry mass accumulation, CGR and CER showed high correlation.

Tiller emission and dry mass accumulation of wheat cultivars under stress

Tillers are important structures for wheat (Triticum aestivum L.) because they contribute to increase the number of spikes per area, enhancing grain yield. Stresses during plants early growth have a sizable effect on tiller production. Three experiments were conducted to evaluate the effects of stresses induced by unevenness in sowing depth, defoliation and differences in soil pH on tiller emission and dry mass accumulation of wheat cultivars. The experiments were carried out in Lages, Southern Brazil, during the winter growing seasons of 2000 and 2001. They were performed in square boxes, under natural conditions of radiation and irrigation. In the first experiment, five types of sowing depths were tested to simulate different systems of unevenness in plant emergence of cultivar Embrapa 16. In the second experiment, two wheat cultivars (BRS 177 and BRS 179) were submitted to four types of main stem defoliation. The third experiment assessed the effects of three levels of soil acidity correction on the tillering pattern of Fundacep 29. Unevenness in sowing depth, alternating pairs of seeds at 3 cm and 5 cm deep, reduced tiller emission and dry mass accumulation. The removal of the first and second main stem leaves reduced significantly BRS 179 tiller dry mass and number and did not affect the tillering pattern of BRS 177. The lack of liming restricted tiller emission and reduced plant dry mass accumulation.

MANEJO DE CULTIVARES DE FEIJÃO DE DIFERENTES HÁBITOS DE CRESCIMENTO NO PLANALTO CATARINENSE. I RENDIMENTO DE GRÃOS

This work was conducted in Lages, Santa Catarina state, Brazil, with the purpose of comparing grain yield of bean cultivars when sowed in the recommended planting date and beyond that period, at three plant populations. The planting dates evaluated were: October 5th (recommended period) and December 2nd. The cultivars used were Irai, BR-6 and Carioca which were tested at 100, 200, and 300000 plants/ha. The grain yield was 57% higher when cultivars were sowed in the recommended planting date than after that period. BR-6 and Carioca showed higher grain yield than Irai. Increasing plant population did not show a marked effect in cultivars grain yield.