@article{mohammadshirazi_mclaughlin_heitman_brown_2017, title={A multi-year study of tillage and amendment effects on compacted soils}, volume={203}, ISSN={["1095-8630"]}, DOI={10.1016/j.jenvman.2017.07.031}, abstractNote={Constructing roads and buildings often involves removal of topsoil, grading, and traffic from heavy machinery. The result is exposed, compacted subsoil with low infiltration rate (IR), which hinders post-construction vegetation establishment and generates significant runoff, similar to impervious surfaces. Our goal was to assess tillage and adding amendments for improving density and maintaining perviousness of subsoils compacted during construction. The effects of tillage with and without amendments on (1) soil compaction, (2) IR, and (3) vegetative growth at five sites in North Carolina, USA were evaluated over a period of up to 32 months. The sites, representing a range of soil conditions, were located at three geographic regions; one in the Sandhills (located in Coastal Plain), one in the mountains, and three in the Piedmont. Amendments varied by site and included: (1) compost, (2) cross-linked polyacrylamide (xPAM), and (3) gypsum. Bulk density (BD) and soil penetration resistance (PR) tests were used to characterize soil physical condition. The IR was measured using a Cornell Sprinkle Infiltrometer. Vegetative growth was evaluated by measuring shoot mass and vegetative cover at all sites and root density at the Piedmont sites. Tillage decreased BD and PR compared to the compacted soil at four out of five sites for observations ranging from 24 to 32 months. Compost was applied to four sites prior to tillage and reduced BD in two of them compared to tillage alone. The IR in the tilled plots was maintained at about 3-10 times that of the compacted soil among the five sites over the monitoring periods. Adding amendments did not increase IR relative to tillage alone except at one Piedmont site, where compost and xPAM increased IR at 12 months and compost at 24 months after site establishment. Vegetative responses to tillage and amendments were inconsistent across sites. Results suggest that tillage is a viable option to reduce bulk density and increase infiltration for areas with compacted soils where vegetation is to be established, and that the effect is maintained for at least several years.}, journal={JOURNAL OF ENVIRONMENTAL MANAGEMENT}, author={Mohammadshirazi, Fatemeh and McLaughlin, Richard A. and Heitman, Joshua L. and Brown, Virginia K.}, year={2017}, month={Dec}, pages={533–541} }
 @article{mohammadshirazi_brown_heitman_mclaughlin_2016, title={Effects of tillage and compost amendment on infiltration in compacted soils}, volume={71}, ISSN={["1941-3300"]}, DOI={10.2489/jswc.71.6.443}, abstractNote={Soils are compacted during land development through soil excavation and heavy equipment traffic. Compacted soils have limited infiltration and are susceptible to erosion. Infiltration can be enhanced by various approaches including tillage and compost addition. The objective of this study was to determine the efficacy of tillage and adding compost to reduce stormwater runoff and sediment loss by improving infiltration in simulated postconstruction soils. Tillage treatments were tested at two sites in the Piedmont region of North Carolina (Piedmont 1 and 2). Prior to applying tillage and amendment, soils at both sites were graded to remove the surface horizon and compacted with a vibratory roller. At Piedmont 1, the treatments were compacted with no tillage, shallow (15 cm [5.9 in] depth) tillage (ST), and deep (30 cm [11.8 in] depth) tillage (DT). At Piedmont 2 the treatments were compacted, DT, and DT with incorporated compost (DT+Com). The grass seed mixtures recommended by the North Carolina Department of Transportation for the location (Piedmont) and time of planting were applied at each site. Runoff volumes (RV) and total suspended solids were measured after each of the first 12 and 13 storm events at Piedmont 1 and 2, respectively. Infiltration rate (IR) and bulk density (BD) were determined five and seven months after establishment at Piedmont 1 and 2, respectively. At both sites, RV and total amount of soil loss were reduced with tillage by 60% to 82% during the monitoring period. Neither deeper tillage nor incorporating compost significantly affected these results. Grass establishment was significantly better with tillage. The IRs measured at the end of the monitoring period were around 1 cm h−1 (0.4 in hr−1) in the compacted treatment but ranged from 19 to 33 cm h−1 (7.5 to 13 in hr−1) in the tilled treatments, again with no effects of tillage depth or compost. The results suggest that tillage to a depth of at least 15 cm (6 in) can be highly effective for improving soil conditions and reducing runoff and erosion from soils compacted as the result of construction activities.}, number={6}, journal={JOURNAL OF SOIL AND WATER CONSERVATION}, author={Mohammadshirazi, F. and Brown, V. K. and Heitman, J. L. and McLaughlin, R. A.}, year={2016}, pages={443–449} }