Soybean root growth and crop yield in reponse to liming at the beginning of a no-tillage system

Analyzing the soil near crop roots may reveal limitations to growth and yield even in a no-tillage system. The purpose of the present study was to relate the chemical and physical properties of soil under a no-tillage system to soybean root growth and plant yield after five years of use of different types of limestone and forms of application. A clayey Oxisol received application of dolomitic and calcitic limestones and their 1:1 combination in two forms: surface application, maintained on the soil surface; and incorporated, applied on the surface and incorporated mechanically. Soil physical properties (resistance to mechanical penetration, soil bulk density and soil aggregation), soil chemical properties (pH, exchangeable cations, H+Al, and cation exchange capacity) and plant parameters (root growth system, soybean grain yield, and oat dry matter production) were evaluated five years after setting up the experiment. Incorporation of lime neutralized exchangeable Al up to a depth of 20 cm without affecting the soil physical properties. The soybean root system reached depths of 40 cm or more with incorporated limestone, increasing grain yield an average of 31 % in relation to surface application, which limited the effect of lime up to a depth of 5 cm and root growth up to 20 cm. It was concluded that incorporation of limestone at the beginning of a no-tillage system ensures a favorable environment for root growth and soybean yield, while this intervention does not show long-term effects on soil physical properties under no-tillage. This suggests that there is resilience in the physical properties evaluated. Analisar o solo próximo às raízes pode revelar limitações ao crescimento e à produtividade das culturas, mesmo em sistema plantio direto. Este estudo teve o objetivo de relacionar algumas propriedades químicas e físicas de solos e o crescimento radicular e rendimento de soja, em decorrência de tipos de calcário e formas de sua aplicação. Na implantação do sistema plantio direto em área de Latossolo Vermelho distroférrico argiloso, foram aplicados calcários dolomítico, calcítico e a combinação de ambos (proporção 1:1), nas formas superficial e incorporado. Cinco anos após a implantação do experimento, foram avaliadas propriedades físicas (resistência à penetração, densidade do solo e agregação do solo) e químicas (pH, cátions trocáveis, H+Al e capacidade de troca de cátions) do solo e da planta (distribuição do sistema radicular e rendimento de grãos de s