The effects of soil water content and bulk density on the compactibility and soil penetration resistance of some Western Australian sandy soils

Abstract

Quantitative models to predict the effects of soil compaction on wheat yields are being developed for the northern sandplains of Western Australia. An understanding of the relationships between soil water content (W), bulk density (p), compactibility and soil penetration resistance (P) is required. Thirteen subsoils from W.A. sandplain soils were tested for compactibility. As the amounts of very coarse sand or clay in the soil increased, the maximum density (�max.) achieved with a standard compactive effort also increased, while the critical soil water content (Wcrit,.) for maximum compactibility declined. The effects of p and W on P were investigated for five of the soils. The value of P was only slightly affected as W was reduced to less than 70% of the field capacity water content. As the soils were dried further, P increased exponentially. At all water contents, an increase in p was found to markedly increase P. Particle size distribution could be used to predict �max. and Wcrit., but could not be related to the effects of changes in p and W on P. The implications for the measurement and effects of soil compaction in the field are discussed.

Análise espacial da ocorrência do índice de cone em área sob semeadura direta e sua relação com fatores do solo

“…O comportamento desses modelos, em ambos os casos, evidencia relação diretamente proporcional com o aumento dos teores de argila e matéria orgânica, resultando em maiores teores de água no solo, em uma função que tende à estabilização, no primeiro caso, e em comportamento linear, no segundo. Por outro lado, solos com maior teor de argila e matéria orgânica tendem a apresentar valores maiores para a capacidade de campo (BRADY & WEIL, 2001), o que aumenta a quantidade de água necessária para alcançar o teor citado por HENDERSON et al (1988), de 70% da capacidade de campo, no qual a diminuição da água aumenta exponencialmente a sua influência na resistência do solo à penetração. Tal situação é indicativa de que não se pode tecer considerações conclusivas a respeito da menor influência no IC, na região com maior teor de água, a qual também apresenta maior teor de argila e de matéria orgânica.…”

Assessing the effects of initial soil characteristics, machine mass and traffic intensity on forest soil compaction

“…Significant soil particle rearrangement hence becomes problematic (Whalley et al, 2005) and the friction experienced by the penetrologger cone increases rapidly. Henderson et al (1988), Vaz et al (2001) and Ampoorter et al (2007) also stated this positive relationship, and reported a logarithmic shape. Although BD remains more or less constant at higher values, PR may still increase.…”

Impact of mechanized logging on compaction status of sandy forest soils

“…Henderson et al (1988), Smith et al (1997), Vaz et al (2001) and Whalley et al (2005), for a wide variety of textural classes ranging from sand to clay. The non-linear behaviour can be explained by the pore space being reduced as bulk density increases.…”