Boundary line approach applied among crop emergence parameters and soil physical properties/ Procedimento "boundary line" aplicado entre parametros de emergencia de culturas e propriedades fisicas do solo

The boundary line technique has been proposed for interpreting biological data where one variable is a biological response and the other is an independent variable. The objective of this study was to correlate maize and soybean emergence parameters with soil seedbed physical properties using a boundary line approach. The study was performed at the experimental farm belonging to the Universidade Estadual de Ponta Grossa, in the municipality of Ponta Grossa, Parana State, Brazil. The area has been managed under a no-tillage system for 18 years. The emergence percentage (EP) and emergence rate (ER) were determined for maize and soybean crops. Soil seedbed physical properties were evaluated for both crop species and included soil penetration resistance, volumetric water content, aggregate stability, tensile strength, friability, saturated soil hydraulic conductivity, bulk density, and the least limiting water range. The boundary line approach was applied to pairs of values of plant emergence parameters and soil seedbed physical properties, and then the regression model was adjusted to the boundary points. The boundary line approach indicated that crop emergence was dependent on soil seedbed physical properties. It was possible to determine the optimum values of soil seedbed physical variables for crop emergence. The boundary line approach is a promising and complementary tool to better understand crop emergence responses to soil seedbed physical properties. Key words: seeds, biological data, soil-plant relations A tecnica "boundary line" foi proposta para interpretar dados biologicos, onde uma variavel e uma resposta biologica e a outra uma variavel independente. O objetivo do trabalho foi correlacionar parametros de emergencia de milho e soja com propriedades fisicas da cama de semeadura do solo aplicando o procedimento "boundary line". O estudo foi conduzido na Fazenda Experimental da Universidade Estadual de Ponta Grossa, em Ponta Grossa, PR. A area e manejada sob sistema plantio direto ha 18 anos. Foram determinados o indice de velocidade de emergencia e a taxa de emergencia para as culturas do milho e da soja. As propriedades fisicas avaliadas na cama de semeadura de milho e soja foram: resistencia do solo a penetracao, conteudo volumetrico de agua, estabilidade dos agregados, resistencia tensil, friabilidade, condutividade hidraulica do solo saturado, densidade do solo e intervalo hidrico otimo. O procedimento "boundary line" foi aplicado aos pares de va