During Summer 1997, soil compaction in agricultural fields was evaluated using a portable electronic cone penetrometer. Rather than requiring the operator to read from an analog scale, this penetrometer stores data in a digital form, which are downloaded to a personal computer for analysis. Soil strength, measured in 1-inch (2.5-cm) increments, can be stored for up to 100 25-inch (64-cm) deep soil profiles. This instrument can be operated by a single person and facilitates collecting large data sets required to characterize highly variable soil environments. Because the penetrometer was designed to measure and formulate predictions about the trafficability of wet soils, it is often incapable of measuring the higher soil resistance occurring in drier agricultural fields. If used soon after rainfall or irrigation, it is useful in detecting hardpans associated with tillage or traffic patterns.
Ortstein (a soil layer cemented by organic carbon, aluminum, and iron; commonly referred to as hardpan) inhibits blueberry (Vaccinum corymbosum) growth. Growers have used deep tillage to break up ortstein, however, the benefits appear to have only been temporary. This study was conducted to determine if 1) crushed ortstein will recement, 2) depodzolizing species will reduce recementation, and 3) a commercially available soil amendment, Super Symbex 4X, will reduce recementation of crushed ortstein. Ortstein from Saugatuck sand (sandy, mixed, mesic Typic Durorthod) was crushed and passed through a 2-mm (0.079-inch) sieve and used in column experiments to assess recementation. Pieces of uncrushed ortstein were added to some columns to evaluate changes in cementation. Aqueous blueberry leaf extracts were added daily to columns for 1.5, 3, 6, and 12 weeks. Duplicate columns were treated with Super Symbex 4X and distilled water. Aqueous leaf extracts from bent grass (Agrostis perennans) and fescue (Festuca rubra) were added for 12 weeks. Solutions of protocatechuic acid (PCA), ρ-hydroxybenzoic acid (ρHBA), catechol and vanillic acid (VA) were added to crushed ortstein and allowed to stand for 5 weeks. Super Symbex 4X was added to the crushed ortstein and mixed with the organic acids at the recommended rate. Extensive recementation (96% aggregation) of crushed ortstein occurred after only 1.5 weeks of treatment with green blueberry leaf extract in the column experiments. Bent grass and fescue leaf extracts caused less and weaker recementation than blueberry. Addition of Super Symbex 4X to ortstein pieces did not produce an increase in size as did blueberry, bent grass and fescue leaf extracts. PCA, ρHBA and VA had high levels of recementation. The water control and catechol did not show high levels of recementation. Addition of Super Symbex 4X to the organic acid and crushed ortstein decreased recementation with the strongly recementing organic acids, PCA, ρHBA and VA. Super Symbex 4X appears to have potential to retard recementing of crushed or broken ortstein. Bent grass and fescue cover crops may not retard recementation of crushed ortstein.
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.
Concentrations of soluble solids (SSC) in fruits of Cucumis melo L., cv. PMR 45, were positively correlated with 2 physical measures of soil samples from producing fields: a) the degree of cracking which occurred during dehydration, and b) the rapidity with which water or a CaSC>4 solution percolated the soils. Very low SSC was associated with sandy, non-cracking soils, which in addition permitted only low rates of percolation. Low SSC also was found to be associated with soils having subsurface hardpans or dense subsoil strata, and also with the distance to lower bounds of plant containers and experimentally placed barriers which obstructed downward root growth. SSC, under adverse conditions, varied further as a function of fruit numbers per plant.
The sensitivity of French prune (Prunus domestica L. syn. `Petite d'Agen') to water deprivation at various fruit growth stages was studied over 3 years in a drip-irrigated orchard. The soil was a poorly drained Rocklin fine sandy loam with a hardpan that varied from 4.75 to I m from the surface at the northern end of the orchard (shallow soil condition) to no hardpan apparent to 2 m below the surface at the southern end of the orchard (deep soil condition). Water deprivation during a) the first exponential phase of fruit growth or stage I, b) lag phase of fruit growth or stage II, c) first half of stage II, d) second half of stage II, e) second exponential fruit growth phase or stage III, and f) postharvest was compared to a fully watered control. Water deprivation caused the most severe reduction in tree water status when it was imposed over longer periods of time and during periods of high evaporative demand and also had mm-e severe effects under shallow soil conditions. Compared to the control treatment, deprivation during all of stage II (the most severe deprivation treatment) was associated with increased Ilowering, reduced fruit hydration ratio, and smaller fruit size under all soil conditions. Under deep soil conditions, deprivation during all of stage II resulted in increased return bloom, which was reflected in higher fruit loads and dry t-ha-' fruit yield. However, under shallow soil conditions, even though return bloom was increased with this treatment, fruit loads and dry t·ha-1 fruit yields were the lowest of all treatments. These differences in treatment effects in shallow vs. deep soil conditions were most likely the result of increased fruit drop, which occurred under shallow soil conditions as a result of rapid onset and increased severity ofstress. Treatments that had parallel effects in shallow and deep soil conditions resulted in statistically significant overall treatment effects, while those that had opposing effects in shallow vs. deep soil conditions did not show significant overall treatment effects. Substantial alternate hearing occurred, and, in general, dry fruit yields above ≈9 dry t·ha-1 resulted in a decrease in fruit load the following year, while loads below this value showed a subsequent increase. Based on a separate estimate of the theoretically stable value for each treatment, all deprivation treatments resulted in a higher sustainable fruit load compared to the fully irrigated control. This suggests that, for the purpose of prune fruit production, there may be an optimal level of tree water stress.
' opinions about high tunnel soil quality were thus gauged in general before they were asked about specific soil observations such as soil surface crusting, visible mineral deposits, clod, or hardpan formation. A response left blank or indicated as “not sure
bark alone. In some instances pine bark amendment alone without added nitrogen or cotton gin waste suppressed plant growth. EFFECT OF LEAF EXTRACTS AND A SOIL AMENDMENT ON RECEMENTATION OF CRUSHED ORTSTEIN Ortstein, a type of hardpan, inhibits blueberry
. SURFACE-FLOW CONSTRUCTED WETLANDS In surface-flow (SF) constructed wetlands, water flows above the sediment or media surface, which is typically a clay or native soil with a subtending hardpan that is relatively impervious to water penetration ( Fig. 1
conduct soil tests ( Knewtson et al., 2010a ). Interestingly, soil quality (measured as clods, surface crusting, mineral deposition, hardpans, and particulate organic matter) in high tunnels does not appear to be adversely impacted by most growers
, 2002 ; Obreza et al., 1997 ). Many of these soils have a hardpan composed of aluminum (Al) and iron (Fe) “cemented” together with organic matter or a subsurface layer of loamy material (a mixture of mostly clay and sand with little silt) that have