Changes in pore structure in a no-till chronosequence of silt loam soils, southern Ontario

Abstract

Many research studies have dealt with the influences of minimum or no-till soil management practices on the major physical, chemical, biological and morphological properties in the soil profile. However little work has been done on the assessment of the rates of changes in pore properties as management practices are converted from conventional to no-till (NT) methods. Short-term changes in soil micromorphology attributed to conversion to no-till from conventionally tilled management are evaluated in this paper. As the number of years in no-till increased there was a decrease in the number pores of 30- to 100-µm diameter in the no-till soils. However, pores from 100- to 500-µm diameter increased in number only after 4 yr of NT. The pores of this size are important for water storage, transmission and root development. The decline in the number of these pores after no-till initiation followed by the increase after 4 yr may explain why crop yields tend to be lower only after the first few years after implementing no-till. The 100- to 500-µm diameter pores may be crucial for the proper development of roots in wheat and corn. The no-till soils had greater numbers of horizontally oriented elongated macropores in the top 5 to 15 cm of the soil profile due to the lack of tillage and annual freeze-thaw processes. These pores may inhibit proper drainage and root penetration. Rounded macropores increased with the number of years the soil was in no-till as these pores were maintained each year due to the lack of tillage and greater faunal activity in the no-till soils. Key words: Micromorphology, image analysis, earthworms, no-till, soil structure

Evolução de propriedades físicas do solo em função dos sistemas de manejo em culturas anuais

“…Em países temperados, constata-se que, em geral, em comparações de sistemas com menos de dez anos, a densidade é maior e a porosidade é menor em PD do que em PC na camada 0 -10 cm (DOUGLAS et al, 1986;HUSSEIN;OLSEN;SIEMENS, 1998;PROTZ;TOMLIN, 1999;SCHJONNING;RASMUSSEN, 2000 e Franzlubbers e Ashad (1996) aos 13 e 16 anos em British Columbia, Canadá.…”

Seasonal changes in soil physical properties under long-term no-tillage

“…Soil disturbance from seeding operations can result in "localized tillage" of the soil surface under NT (da Silva et al, 1997 and thus impact soil physical quality. Usually it has been considered that stabilization of soil properties is reached after about five years of continuous NT (VandenBygaart et al, 1999;Rhoton, 2000;Alvarez et al, 2009). However, short-term changes in soil physical properties may be driven by different factors such as agricultural machinery, soil type, topography, climate and crop selection (Strudley et al, 2008).…”

Earthworms and agricultural systems: Status of knowledge and research in Canada

“…Shipitalo and Protz (1987) observed that no-till had approximately half the macroporosity (pores ≥ 200 µm) in the Ap horizon when compared to conventional tillage but noted that earthworm and other soil faunal activity resulted in two to nine times more bioporosity than in the conventionally tilled soil. VandenBygaart et al (1999) showed evidence of earthworm activity in soil profiles of an 11-yr no-till and conventionally tilled silt-loam sampled to 30-cm depth. The burrowing activity of earthworms in notill systems makes a major contribution towards soil functioning to partition air and water flow.…”