Four techniques for compaction amelioration were studied: 1) Vertical drainage panels; 2) vertical gravel-filled sump drains; 3) soil trenches filled with sandy loam; and 4) peat amended back fill. The control was backfilled with existing soil on the site. Vertical drainage mats and vertical gravel-filled sump drains were shown to increase O2% in surrounding soil; however, all O2 levels regardless of treatment were above what is considered limiting. Shoot and root growth of Pyrus calleryana `Redspire' was greatest for treatments that alleviated mechanical impedance (soil trenches and amended back fill) and least for treatments that did not (controls and vertical drains). Vertical drainage mats which alleviated mechanical impedance to a lesser degree showed intermediate growth.
roots. Different potting media led to an increase in the root number and length; however, the cause is unknown.
The data support the conclusion that new root growth from ‘PRI 73-50’ slips was limited by mechanicalimpedance to growth
A 3-year field study conducted on an Eel silt loam soil (Aquic Udifluvent) compared cabbage (Brussica oleracea L. capitata group), cucumber (Cucumis sativus L.), snap bean (Phaseolus vulgaris L.), and sweet corn (Zea mays L.) for their growth and yield response to an artificially compacted soil layer beginning at about the 10-cm depth. Slower growing cabbage seedlings in compacted plots were more subject to flea beetle damage than the uncompacted controls. Prolonged flooding after heavy rainfall events in compacted areas had a more adverse effect on cabbage and snap bean than on cucumber or sweet corn. Sweet corn showed almost no growth reduction in one of the three years (1993) when relatively high fertilizer rates were applied and leaf nitrogen deficiencies in compacted plots were prevented. Maturity of cabbage, snap bean, and cucumber was delayed, and the average reduction in total marketable yield in (direct-seeded) compacted plots was 73%, 49%, 41%, and 34% for cabbage, snap bean, cucumber and sweet corn, respectively. Yield reduction in transplanted cabbage (evaluated in 1993 only) was 29%. In a controlled environment greenhouse experiment using the same soil type and similar compaction treatment as the field study, compaction caused a reduction in total biomass production of 30% and 14% in snap bean and cabbage, respectively, while cucumber and sweet corn showed no significant response. The growth reductions of snap bean and cabbage in the greenhouse could not be attributed to compaction effects on soil water status, leaf turgor, nutrient deficiency, or net CO, assimilation rate of individual leaves. Root growth of sweet corn was least restricted by the compacted soil layer. The contrast between our field and greenhouse results indicates that the magnitude of yield response to compaction in the field was often associated with species sensitivity to secondary effects of compaction, such as prolonged flooding after rainfall events, reduced nutrient availability or uptake, and prolonged or more severe pest pressure.
et al., 2015 ; Svistoonoff et al., 2007 ). There is also substantial evidence that supports the role of soil compaction or mechanicalimpedance on root growth in plant species ( Lipiec et al., 2012 ; Oussible et al., 1992 ; Taylor and Brar 1991
be a good predictor of the effect of mechanicalimpedance and substrate pore size, because data obtained by Baligar and Nash (1978) and Wiersum (1957) demonstrate that a root is only able to penetrate a pore that has a diameter exceeding that of a
Ferrini, 2006 ). They are also susceptible to mechanicalimpedance in the soil ( Materechera et al., 1992 ); thus, low bulk density can improve posttransplant root growth. Bulk density was generally lowest and chemical properties more favorable for PB and
The response of roots to mechanicalimpedance has intrigued horticulturists, plant biologists, and substrate physicists for at least two centuries ( Araki and Iijima, 2001 ; Atwell, 1993 ), whereas the model of root growth as a function of multiple
States range from 15 to 40 mol·m −2 ·d −1 compared with 25 to 60 mol·m −2 ·d −1 in the southwestern United States ( Korczynski et al., 2002 ). Mechanicalimpedance of light by glazing materials and greenhouse support structures reduces transmission of
aeration, mechanicalimpedance and tree establishment J. Environ. Hort. 13 64 71 Day, S.D. Harris, J.R. 2008 Growth, survival, and root system morphology of deeply planted Coryluys colurna seven years after transplanting and the effects of root collar