Indicadores de qualidade física em solos sob diferentes sistemas de uso e manejo

• Autor(a) principal: Blainski, Éverton
• Data de Publicação: 2010
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Repositório Institucional da Universidade Estadual de Maringá (RI-UEM)
• Texto Completo: http://repositorio.uem.br:8080/jspui/handle/1/1149
• topic: Solo; Qualidade física; Indicadores; Irrigação; Solo adequado para Agricultura; Plantio direto; Nitossolo Vermelho Distroférrico; Intervalo Hídrico Ótimo (IHO); Qualidade física do solo; Curva de resistência do solo à penetração; Intervalo hídrico ótimo; Sistema de plantio direto; Brasil.; Soil physical quality; Soil resistance to penetration curve; Least limiting water range; Irrigation; No-tillage systems; Brazil.; Ciências Agrárias; Agronomia

Soil is a natural basic finite resource to agroecossystems. The substitution of natural landscape by agricultural systems has caused huge impacts, mainly due to soil physical degradation. This way, the comprehension and quantification of these impacts are primal to modern agriculture sustainability and maintenance of soil physical quality (QFS). The influence of QFS on crops yield can be related to a straight relationship between crop development and fundamental physics factors for plants growth. QFS can be expressed through soil indicators as the soil resistance to penetration curve (CRP) and least limiting water range (IHO). The CRP integrates soil resistance to penetration (RP) as a function of soil bulk density (Ds) and water content (θ) and can be used to establish both θ and critical soil bulk density (Dsc), in which RP is restrictive for root growth. At this study, the CRP was used as an indicator of physical degradation in an Oxisol under four use and management systems: native forest, pasture, citrus and annual crops. Results showed that CRP was modified by use and management systems and dependent on Ds and θ. An increase on θ is needed to keep RP less than critical RP for soils under annual crops and citrus when compared with native forest and pasture, pointing to physical degradation of these areas. θ was the variable that mostly presented influence on RP, mainly on soils with degraded structure, being one of the strategies to keep RP lower than the restrictive limit for plants growth. To evaluate the effect of θ management in controlling the soil physics restriction, mainly RP, the IHO was used, since it integrates the CRP and variables related to θ and aeration (PA). IHO was determinate on an irrigated Rhodic Kandic and its use was proposed for irrigation management. The results showed that the adoption of soil water potential (Ψ) at -800hPa as a limit to start irrigation establishes limitations to plants due to RP restrictions on areas with high values of Ds. At this case, mapping the area with homogeneous Ds could be used to regionalized management of Ψ in order to keep RP less than critical RP. On areas with lower values of Ds, can occur a major soil drought without RP being over the critical assumed value. For areas with Ds greater than Dsc, an increase of θ did not decrease soil physics restrictions, being necessary to adopt actions in order to provide Ds reduction. Besides the irrigation, θ management to control QFS can be done, under no-tillage systems (SPD), through keeping mulching on soil surface, with decreased evaporation and increased θ availability. For this, IHO was determined to an Oxisol, cropped with soil beans, on SPD, and θ was measured under different oat mulching rates: 0, 3, 6, 9 and 12Mg of dry matter per hectare and from this on, the frequency of θ inside the IHO (Fdentro) was determined. The IHO reduction resulted on less Fdentro, independently of soil mulching. On the other hand, the mulching rate increase provided more Fdentro, although dependent on Ds. When Ds levels were close to Dsc,θ increasing provided by mulching, did not reduce the soil physical restrictions, due to reduced IHO amplitude. On this case, the reduction of Ds levels can provide an increase of Fdentro due to the extension of IHO. The reduction of Ds associated with the mulching maintenance on soil surface could guarantee adequate physical conditions for plant growth on soils under SPD.