Lisandro Rambo

Grain yield and kernel crude protein content increases of maize hybrids with late nitrogen side-dressing

Physiological changes incorporated into current maize hybrids suggest the occurrence of modifications in the nitrogen uptake dynamics, improving plant ability to uptake N during grain filling. This may justify late N side-dressing whenever environmental constraints prevent adequate nitrogen supply during crops vegetative development. This study evaluates effects of nitrogen fertilization at booting and silking on grain yield and kernel crude protein contents of commercial maize hybrids. Two experiments were set up in Eldorado do Sul, RS, during the 2001/2002 and 2002/2003 growing seasons. In 2001/2002, treatments were composed of two hybrids (Agroceres 303 and Pioneer 32R21), three nitrogen rates applied during maize vegetative development (30, 80 and 130 kg ha -1 ) and three nitrogen rates applied at silking (0, 50 and 100 kg ha -1 ). In 2002/2003, four hybrids (Agroceres 303, Pioneer 32R21, Dekalb 215 and Syngenta Penta) and four nitrogen rates side-dressed at booting (0, 50, 100 and 150 kg.ha -1 ) were assessed. There were significant increments in grain yield and kernel crude protein content with nitrogen fertilization at booting and silking. Grain yield response to late N side-dressing differed among cultivars. The impact of nitrogen fertilization at silking was higher at the smallest rate of N during the plant vegetative development. Enhancements in grain yield with late N side-dressing resulted from increases in grain weight. Modern hybrids can uptake nitrogen during silking, contradicting the hypothesis that late N side-dressing is not efficient to improve maize grain yield.

Desempenho agronômico e econômico do milho em diferentes níveis de manejo e épocas de semeadura

The objective of this work was to evaluate agronomic and economic performance of maize in five management levels and three sowing times. The experiment was conducted in 2001/2002 and 2002/2003, in Eldorado do Sul, RS, Brazil. Treatments consisted of three sowing times (August, October and December) and five management levels (low, average, high, potential I and II) which varied in relation to the soil winter cover, cultivar, plant arrangement and the level of chemical fertilizer, water supply and weed, insect and disease control. A randomized block design was used with split-plots and four replications. Sowing times were located in the main plots and the management level in the split-plots. The increments in maize yield in response to investments in management and cultivar were higher in August and October, and resulted in higher economic return, mainly in October. In December sowing, there was no economic return for the highest investment in management level. In August and October, it was possible to associate maximal economic and technical efficiencies through the management level increase and the choice of the greater potential yield cultivar. Index terms: Zea mays, agronomic and economic efficiency, cultivars, water regime, grain yield, gross margin.

Parâmetros de planta para aprimorar o manejo da adubação nitrogenada de cobertura em milho

Maize is one of the most demanding grasses in terms of nitrogen fertilization. There is a need to estimate accurately the amount of N applied to the soil so that this crop can be properly supplied during its whole cycle. The soil organic matter content, grain yield expectation and N contribution from the decay of the preceding crop are the parameters currently used in the States of Rio Grande do Sul and Santa Catarina, Brazil, to define maize nitrogen rates. Nitrogen has a complex dynamics in the soil. Furthermore, the crop’s ontogeny interferes substantially with N demand. Considering such variations, other parameters can help to improve the management of N side-dress fertilization in maize. Several plant parameters have been used to indicate N level in the tissue. Among them, the nitrate content in the stem, the nitrogen content and accumulation in the leaf or plant and the relative chlorophyll content in the leaf deserve special consideration. The estimation of leaf chlorophyll content through a portable chlorophyll meter have been intensively studied in the last years because it is fast, cheap and efficient. This review has the purpose of describing the major plant parameters that can be used as indicators of the plant nitrogen level in order to foresee the need of N side-dress application in maize, aiming to enhance the N use efficiency and to decrease the environmental impact of N application.

Desenvolvimento fenológico e agrônomico de três híbridos de milho em três épocas de semeadura

Variations in environmental conditions determined by different sowing dates have a great influence on maize ontogeny. This experiment was carried out to evaluate the phenological development of three maize hybrids, at three sowing dates. The experiment was carried out at the Depressao Central region of the state of Rio Grande do Sul-Brazil during 2000/2001 grows season. The single-cross very early hybrid Pioneer 32R21, the single-cross early hybrid Dekalb 214, and the double-cross normal hybrid Agroceres 1051 were evaluated at 08/22/2000 (early), 10/31/2000 (intermediate) and at 01/25/2001 (delayed) sowing dates, with no supplemental irrigation. All hybrids presented shorter developmental subperiods when sowing was delayed. Tassel and ear differentiation occurred, respectively, in the stages of 6 to 7 and 10 to 11 completely expanded leaves, regardless of hybrid cycle and sowing date. The highest leaf emission rate occurred when very early hybrid was sown in October. Delaying sowing resulted in a reduction of leaf area per plant mainly in early hybrids. Number of spikelets per ear, grain yield and grain weight were generally higher in October than in the other two sowing dates.

Caracterização dos acidentes com tratores agrícolas

Despite its importance, few researches have been carried out characterizing work accidents involving agricultural tractors. The objective of this work was to characterize the accidents with agricultural tractors, to determine more efficient ways to prevent them. A questionnaire was applied to an ample of agricultural tractor operators from the Central Region of Rio Grande do Sul State. Results showed that 39% of the agricultural tractor operators analyzed had already suffered some kind of accident. The most frequent type of serious accidents was tractor overturning which occurred in 51.71% of the cases. Slips were the most important slight accident. The most important causes of accidents were lack of knowledge about safety procedures on tractor operation (32.77%), lack of attention (32.22%) to the task carried out and inadequate equipment (22.22%). There were great differences between the causes of serious and slight accidents. Operators without adequate training, no observation of some important safety procedures and very long working day were reported in this research, collaborating to increase the occurrence of accidents. Finally, it is necessary to incorporate confort and security devices, as well as training the agricultural tractor operators, to prevent future accidents.

Testes de nitrato no solo como indicadores complementares no manejo da adubação nitrogenada em milho

Recently, nitrogen fertilization recommendation has had an expressive advance in Southern Brazil, when it began to take into account the contribution of the previous cover crop for the soil nitrogen (N) availability, in addition to organic matter and yield goal. Improvement of N management is constantly aimed. In this respect, there is a high potential to include soil and plant parameters as complementar indicators of soil N level, mainly in high yield systems and with high rates of N application. Within the soil parameters considered, one of the most impartant is the nitrate tests, which represent the readily available N and are known as intensity tests. According to the time of soil sampling, nitrate tests can be classified as: preplant soil nitrate test (PPNT), pre-sidedress soil nitrate test (PSNT), and post-harvest soil nitrate test (PHNT). Within these tests, one of the most important is the TPNC, which have been more studied and used, mainly in the EUA, because it allows the evaluation of the soil N availability during the crop development. It makes possible the management of nitrogen fertilization in specific situations. This review has the purpose of discussing the potential use of soil nitrate tests to evaluate N availability during crop development and to predict N requirements in maize. The hypothesis is that nitrate tests utilization result in higher flexibility of N fertilization management in this crop.

Estimativa do potencial de rendimento por estrato do dossel da soja, em diferentes arranjos de plantas

The soybean yield potential can be modified by plant arrangement. This modification might be the result of the diferential contribution of the canopy strata for the potential determination. The experiment was conducted at the Agronomic Experimental Estation of the Universidade Federal do Rio Grande do Sul, in Eldorado do Sul, Rio Grande do Sul, Brazil, in the 2000/01 growing season. The objectives were to evaluate the yield potential by stratum of soybean canopy in different plant arrangement, under two water availability. The cultivar tested was BRS 137, in no-till planting. Water availability (irrigated an no irrigated), row spacing (20 and 40cm) and population levels (20, 30 and 40 plants m-2) were tested. The yield potential was estimated in the beginning of grain filling (R5). It was considered that all flowers and pods present at this stage were able to reach maturation, forming grains and contributing to yield. The canopy was divided in three strata by plans paralel to soil surface. The irrigated treatment (14976kg ha-1) presented larger total plant yield potential and yield in R8 (maturity) than without irrigation (12148kg ha-1), similar to what ocurred in all soybean canopy strata. The plant arrangement with 20cm of row spacing, independent of population, presented, on the average, larger yield potential in R5 (14970kg ha-1) compared to 40cm row spacing (12154kg ha-1). The same was also noticed at the medium soybean canopy stratum. At maturity the plant arrangement 20cm of row spacing and population of 20 plants m-2 yielded more than 40cm (6442kg ha-1 compared to 4396kg ha-1), due to larger yield at the medium and botom stratum. There was a linear decrease in yield potential with increase of plant population, with row spacing reduction (20cm), explained by the same behavior of the canopy strata. Similar response was obtained for yield in R8. The soybean canopy strata contributed differently to yield potential with the plant arrangement modification, due to the diferential number of reproductives structures (R5) and yield components (R8) alteration.

Tolerância da soja ao desfolhamento afetada pela redução do espaçamento entre fileiras

The row spacing reduction from 40 to 20 cm increase radiation interception, leaf area index and grain yield. This experiment aimed to evaluate if the row spacing reduction influence soybean tolerance to loss of photosynthetic area. The research was performed using no-till tillage system at the Agronomic Experimental Station of Universidade Federal do Rio Grande do Sul, during the 2000/01 growing season. Treatments were arranged in a split-split plot randomized complete block design, with four replications. Treatments included five combination of defoliation in three stages of development (V9 - ninth-node, R2 - full bloom and R5 - beginning of seed filling), two row spacings (20 and 40cm) and four defoliation levels (0 - control, 33, 67 and 100%). The cultivar tested was FT-Abyara. Defoliations performed at the reproductive stages decrease grain yield, especially when curried at the begging of grain filling (R5). The control grain yield was 21% higher when soybean was sown with rows 20cm apart (4134kg ha-1) than with 40cm rows (3413kg ha-1). Narrow rows always provided higher yields in all defoliation levels. The component that influenced yield the most was the number of pods m-2. These results indicate that row spacing reduction from 40cm to 20cm is a positive management strategy for soybean production regardless of defoliation level.

Qualidade de grãos de duas cultivares de soja em função da disponibilidade de água no solo e arranjo de plantas

The soybean is a crop with high demand for nitrogen (N) due to the grain protein content of about 40%. Because of the high protein, soybean is of great economic importance. The present study had its objectives to determine the effect of water availability and soybean plant arrangement on grain quality of two cultivars. With this objective, an experiment was performed during the 1998/99 growing season, in the Agronomic Experimental Station of the Federal University of Rio Grande do Sul (EEA/UFRGS), Eldorado do Sul, RS. The treatments were arranged in a randomized complete-block in a split split-plot design, with four replications. Two water availability (irrigated and not irrigated), two cultivars (BRS 137 and BRS 138) and three row spacings (20cm, 40cm and 20-40cm in skip row) were tested. The leaf N content was evaluated during crop growth, and the protein and oil content, as well as the size and weight of the grains, at the harvest. The average grain yield was of 3360kg ha -1 . The irrigation increased grain yield by 1101kg ha -1 (39%), due to the increase in leaf N, size and weight of the grain. The yield of the cultivar BRS 137 was 535kg ha -1 (17%) greater, as well as it produced grains with larger size, weight and protein content than BRS 138. In the late reproductive stage, leaf N was higer in 20cm and 40cm, what resulted in larger protein content and grain yield 18 and 13% higher, compared to 20-40 cm in skip row, respectively. The grain oil content was not altered by the treatments.

Métodos para a estimativa do potencial de rendimento da soja durante a ontogenia

O objetivo deste trabalho foi estudar metodos para a estimativa do potencial de rendimento da soja durante a ontogenia. Os experimentos foram realizados em Eldorado do Sul, RS, durante as safras de 1996/1997, 1999/2000 e 2000/2001. Os tratamentos constaram de cinco cultivares de soja, FT-Saray, IAS 5, IAS 4, FT-Abyara e FEPAGRO RS-10. Cinco metodos foram utilizados para estimar o rendimento que seria obtido se todas as estruturas reprodutivas presentes no florescimento e no inicio do enchimento de graos, produzissem graos na maturacao. O potencial de rendimento no florescimento e no enchimento de graos, apresentou alta correlacao com o numero de flores e estruturas reprodutivas, respectivamente. Verificou-se, tambem, correspondencia entre os metodos. Nao houve, na maioria das vezes, correlacoes significativas entre o potencial, no florescimento e enchimento de graos, e o rendimento de graos na maturacao. Os metodos estudados constituem ferramentas importantes para o manejo, quando utilizados para comparar o potencial de rendimento durante a ontogenia.