ABSTRACT The automatic control of section shut-off in seed drills minimizes seeding overlap and can reduce productivity losses, especially in responsive crops such as corn. In that context, this study evaluated the effect of sowing overlap on the grain yield and productivity of three corn hybrids. A DB-50 precision seed drill, with 33 rows equipped with a 16-row automatic section control, was used in this experiment. A randomized block design was applied to test three corn hybrids under two sowing conditions (without sowing overlap - WOSO; and with sowing overlap - WSO), with four replications. The analyzed variables were the number of plants per hectare, the number of cobs per hectare, cob length, the number of grains per cob, the thousand grain weight, and productivity. WOSO areas presented cobs that were larger and had more grains, as well as a higher thousand grain weight, resulting in a productivity 13% higher than that of WSO areas. Therefore, the use of automatic section control is a technically feasible alternative to reduce seed costs and avoid productivity losses in corn crops.

ABSTRACT In agricultural areas with a historical of systematic soil sampling, alternative methodologies such as directed sampling design based on management zones (MZ) have been proposed to reduce sampling costs. The aim of this study was to evaluate the technical and economic impacts of replacing a dense systematic soil sampling design (cell size of 0.5 ha) by a systematic sampling with a smaller number of samples (cell size ranging from 1 to 4.5 ha), directed or conventional sampling design on the mapping of soil plant-available phosphorus (P), exchangeable potassium (K), and pHwater. The study was carried out in an agricultural area of 120 ha with soil classified as an Oxisol. The directed sampling designs were based on MZ delimited from data of elevation and overlapping of crop yield maps. Our finding revealed that systematic samplings with grids larger than 2 ha were not efficient to detect the spatial variability of soil P, K and pHwater. Larger systematic grid sizes, directed and conventional sampling design resulted in more generalist thematic maps, losing information about spatial variability of the soil attributes. Thus, from a technical point of view, soil sampling designs with a low density were little efficients, particularly for mapping P and K, due to their higher spatial variability. However, because soil P and K contents were close to or above critical levels and soil acidity was low (average pH close to 5.5), the different sampling designs presented little influence on fertilizer and liming recommendations. Therefore, we concluded that systematic soil sampling design may be replaced by soil sampling directed based on MZ or even by conventional sampling in soils with high fertility to reduce sampling costs. Nevertheless, crop responses must be monitored to validate fertilization management based on these simplifications on soil sampling procedure.

RESUMO Este estudo teve como objetivo avaliar o efeito de diferentes manejos com dejeto líquido de suíno (DLS) e bovino (DLB) na produtividade de matéria seca e de grãos da cultura do trigo e o potencial de estimativa dessa variação com os índices de vegetação NDVI (índice de vegetação da diferença normalizada) e NDRE (índice de vegetação da diferença normalizada pelo red-edge). O experimento foi conduzido em Frederico Westphalen, RS, no delineamento experimental blocos ao acaso, em esquema fatorial 2 x 7, com quatro repetições, sendo duas fontes (DLS e DLB) e sete formas de aplicação superficial e subsuperficial, com e sem o uso de dicianodiamida (DCD), ficando assim distribuídos: testemunha sem aplicação de dejetos e DCD; testemunha sem aplicação de dejetos e DCD, porém apenas escarificada com a máquina de injeção; aplicação dos dejetos em superfície; aplicação dos dejetos em superfície com DCD; injeção dos dejetos em subsuperfície; injeção dos dejetos em subsuperfície com DCD; e aplicação de NPK na forma mineral. No florescimento da cultura do trigo, realizou-se a coleta de matéria seca e as leituras de NDVI e NDRE, e por fim, quantificou-se a produtividade de grãos. Constatou-se que, para DLS e DLB, os melhores resultados em produtividade de matéria seca e de grãos foram para os manejos com injeção em subsuperfície e com injeção em subsuperfície com DCD respectivamente. Dos índices de vegetação, apenas o NDVI foi eficiente em estimar as variações no manejo para a fonte DLB para a produtividade de matéria seca e de grãos do trigo.

ABSTRACT This study aimed to evaluate the effect of different managements with pig slurry (PS) and cattle slurry (CS) on wheat dry matter and grain yields, and the potential to estimate this variation with the NDVI (normalized difference vegetation index) and NDRE (normalized difference red edge index) vegetation indices. The experiment was conducted in Frederico Westphalen-RS, Brazil, in a randomized block experimental design, in a 2 x 7 factorial scheme with four replicates and seven forms of surface and subsurface application, with and without the use of the dicyandiamide (DCD) nitrification inhibitor, distributed as follows: control without application of slurry and DCD; control without application of slurry and DCD, but scarified only with the injection machine; surface application; surface application with DCD; subsurface injection; subsurface injection with DCD; and application of NPK in mineral form. At flowering of the wheat crop, dry matter was collected and readings of NDVI and NDRE were taken, and finally grain yield was quantified. For PS and CS, best results of dry matter and grain yields were found in managements with subsurface injection and subsurface injection with DCD, respectively. Among the vegetation indices, only NDVI was efficient to estimate variations in the management using CS for wheat dry matter and grain yields.

RESUMO O potencial produtivo das áreas agrícolas associados ao arranjo espacial de plantas pode determinar a qualidade fisiológica de sementes de soja (Glycine max L.). Neste sentido, o estudo teve por objetivo avaliar a qualidade fisiológica de sementes de soja oriundas de diferentes ambientes de produtividade e densidade de plantas. Os experimentos foram conduzidos em Boa Vista das Missões, RS, na safra 2014/2015. Ambientes de produtividade foram definidos através da sobreposição de mapas de colheita das safras 2008, 2009/2010 e 2011/2012. O delineamento experimental foi o de blocos ao acaso, em esquema fatorial 2 x 5, com dois ambientes de produtividade (baixa e alta) e cinco densidades de plantas, com quatro repetições. As cultivares utilizadas foram: Brasmax Ativa RR (10, 15, 20, 25 e 30 plantas m-1) e Nidera 5909 RR (5, 10, 15, 20 e 25 plantas m-1). As sementes colhidas foram submetidas às análises de primeira contagem, germinação, plântulas anormais, sementes mortas, condutividade elétrica, envelhecimento acelerado, comprimento de raiz, hipocótilo e plântulas. A variabilidade espacial do vigor pode ser reduzida no campo de produção ajustando-se a densidade de plantas, contudo o ajuste deve considerar a cultivar. A colheita otimizada pode permitir a separação de lotes com maior vigor, oriundos de ambientes de alta produtividade.

ABSTRACT Yield potential of agricultural fields associated with plant spatial arrangement could determine the physiological quality of soybean (Glycine max L.) seeds. Thus, this study aimed to evaluate the physiological quality of soybean seeds from different yield environments and plant densities. Experiments were carried out in Boa Vista das Missões-RS, Brazil, during the 2014/2015 growing season. Yield environments were delineated by overlapping yield maps from the 2008, 2009/2010 and 2011/2012 growing seasons. The experimental design was a randomized complete block in a 2 x 5 factorial arrangement with two yield environments (low and high) and five plant densities, with four replicates. Two varieties were tested: Brasmax Ativa RR (10, 15, 20, 25 and 30 plants m-1) and Nidera 5909 RR (5, 10, 15, 20 and 25 plants m-1). After harvested, the seeds were analysed as following: first count index, germination, abnormal seedlings, dead seeds, electrical conductivity, accelerate aging test, root length, hypocotyl length and seedling length. The spatial variability of seed vigor in the production field could be reduced by adjusting plant density, but the adjustment should consider the variety. Harvest according to yield environment is a strategy to separate lots of seeds with higher vigor, originated from high-yield environments.

RESUMO Realizou-se este estudo com o objetivo de avaliar o uso de diferentes densidades de semeadura e espaçamentos entre fileiras sobre a produtividade de grãos e biomassa, na cultura do tremoço branco cultivar comum. O delineamento experimental foi o de blocos ao acaso, em esquema fatorial 4 x 4, com quatro espaçamentos entre fileiras (20, 40, 60 e 80 cm) e quatro densidades na fileira de semeadura (10, 15, 20 e 25 plantas m-1) com quatro repetições. As variáveis avaliadas foram: produtividade de grãos, massa de cem grãos, massa verde e seca da parte aérea e os teores de nitrogênio, fósforo e potássio no tecido vegetal. A maior produtividade de grãos foi obtida com espaçamento entre fileiras de 20 cm, independente da densidade de plantas. A densidade de 25 plantas m-1 e o espaçamento entre fileiras de 20 cm aumentaram a produtividade de massa verde e seca. O ajuste da densidade de plantas e do espaçamento entre fileiras não alterou os teores de nitrogênio, fósforo e potássio no tecido vegetal.

ABSTRACT The study aimed to evaluate different sowing densities and row spacings on grain yield and biomass in the white lupine crop, cv. ‘Comum’. The experimental design was a randomized block in a 4 x 4 factorial scheme, with four row spacings (20, 40, 60 and 80 cm) and four sowing densities in the row (10, 15, 20 and 25 plants m-1), with four replicates. The evaluated variables were: grain yield, hundred-grain weight, fresh and dry matter and the contents of nitrogen, phosphorus and potassium in the plant tissue. The highest grain yield was obtained with row spacing of 20 cm, regardless of plant density. The density of 25 plants m-1 and row spacing of 20 cm increased the fresh and dry matter yield. The adjustment of plant density and row spacing did not affect the content of nitrogen, phosphorus and potassium in plant tissue.