surface compost effect on hydrology: in-situ and soil cores
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Surface Compost Effect on Hydrology: In-Situ and SoilCoresS. D. Logsdona & R. W. Maloneaa USDA-ARS, NLAE, Ames, IowaPublished online: 07 Nov 2014.
To cite this article: S. D. Logsdon & R. W. Malone (2015) Surface Compost Effect on Hydrology: In-Situ and Soil Cores,Compost Science & Utilization, 23:1, 30-36, DOI: 10.1080/1065657X.2014.949909
To link to this article: http://dx.doi.org/10.1080/1065657X.2014.949909
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Surface Compost Effect on Hydrology: In-Situand Soil Cores
S. D. Logsdon and R. W. Malone
USDA-ARS, NLAE, Ames, Iowa
ABSTRACT. Compost increases water-holding capacity and total porosity. Improved soil structuremay increase volume of macropores, allowing better drainage, air-exchange, and root growth. Thepurpose of this study was to compare water retention curves and hydraulic conductivity for packedcolumns with and without additions of surface compost. Columns packed with subsoil (around 60 cmlong) had either compost or topsoil added to the surface. Tensiometers and hydra probes monitoredsoil pressure head and water content during three wetting and evaporation cycles. The columns withcompost had significantly smaller bulk density at the surface than columns with topsoil (0.87 versus1.34 g cm3). Surface compost amendment resulted in more water when satiated (0.617 versus0.422 m3 m3) and at 100 cm head (0.377 versus 0.276 m3 m3) than for topsoil at the surface,indicating a greater fraction of larger pores for the compost amended. Whole column infiltration ratewas significantly faster for columns with compost than without (1.46 versus 1.11 cm min1);however, saturated hydraulic conductivity (rate water flows through soil) on soil cores was notsignificantly affected by compost. Subsoil water flow and drainage was not significantly affected bysurface compost. For the subsoil, in-situ column drying was significantly drier than core drainage atthe wet end. There were no significant differences in whole column or surface water retention orevaporation rate. Perhaps the trend towards better water-holding capacity in the compost treatmentwas offset by larger pores and faster drainage, resulting in no significant difference between compostand topsoil.
Urban soil is often compacted after construc-tion. The original topsoil has been removedwith only minimal topsoil added after construc-tion. The compaction hinders growth of lawns,shrubs, and trees (ONeil and Carrow 1983).Infiltration is reduced, which results inincreased runoff and erosion (Maniquiz et al.2009).
Faucette et al. (2005) showed that surfacemulch significantly reduced runoff comparedwith the control without surface mulch. Persyn
et al. (2004) showed that various types of sur-face-applied compost all significantly reducederosion compared with non-vegetated or vege-tated controls without compost for highwayconstruction areas. Tyner et al. (2011) showedthat surface-applied mulches and composts allreduced erosion on construction sites, but ero-sion control mats reduced erosion the most.
Johnson et al. (2006) added compostedmanure to the surface of turf, but did notobserve any effect on soil water content. Singeret al. (2006) showed that surface applied com-post only increased soil water right after a rain;
This article not subject to US copyright law.Correspondence to: S. D. Logsdon, USDA-ARS, NLAE, 2110 University Blvd., Ames, IA 50010.
Compost Science & Utilization, 23:3036, 2015ISSN: 1065-657X print / 2326-2397 onlineDOI: 10.1080/1065657X.2014.949909
however, incorporated compost more fre-quently increased soil water content.
Compost sometimes increases water holdingcapacity in the compost addition (Cogger 2005;Giusquiani et al. 1995), but the effect on sub-soil is not clear. Since water content isincreased at both the wet and dry end, the plantavailable water may not be increased by com-post additions (Cogger 2005). The purpose ofthis study was to compare water retentioncurves and hydraulic conductivity for packedcolumns with and without additions of surfacecompost.
MATERIALS AND METHODS
Six polyvinyl chloride (PVC) columns werebuilt for the study, having a diameter of 30 cmand a drainhole. The columns were packedlayer-by-layer with Nicollet clay loam subsoil(fine-loamy, mixed, superactive, mesic AquicHapludoll; Soil Survey Staff 2010). Then, 160to 180 mm of water were added and the col-umns were covered to equilibrate. Surface addi-tions were either 3 cm of soil (treatment 1) oryard-waste compost (treatment 2), resulting inthree replicates of each treatment. The compostwas 1.7% total nitrogen, 0.27% total phospho-rus, 0.83% total potassium, 34.8% organic car-bon with a pH of 7.5 and with 91% of particles
Saturated hydraulic conductivity was deter-mined by the falling head method (Klute andDirksen 1986), followed by desorption. Thenthe samples were dried to determine bulk den-sity (Blake and Hartge 1986). Leaks in some ofthe Tempe cells occurred, resulting in somemissing data. At the most negative pressurehead (700 cm), only 9 of the 36 cores did notleak, so the 700 cm data are not used. At500, 300, and 100 cm head levels, 24, 30,and 34 of the cores provide useful non-leakingdesorption data, but all 36 cores had satiateddata (near saturation with some free drainage).These head levels were used even with themissing data. Intermediate head levels (50,200, 400) were interpolated between themeasured data.
Instantaneous profileevaporation calculatedwater retention curves were compared withTempe cell data. The instantaneous profilemethod interpolates soil water and pressurehead simultaneously from measurements,whereas pressure heads are applied to theTempe cells. Also, the columns with compostwere compared to the columns with surfacetopsoil for instantaneous profile desorption, andfor undisturbed core Ksat, bulk density, anddesorption. Hydraulic conductivities were log-transformed for statistical comparisons thengeometric means were given for presentation.
Calibrated load cells installed at the base ofthe columns were used to assess change in soilwater within each column. Mass balance frominflow, outflow, and load cells was calculated.For each cycle and column, the amount of drain-age was subtracted from the amount of wateradded, and divided by the soil volume. Themaximum wetting indicated by the load cellwas converted to cm3 and divided by the soilvolume. The one day drainage after this maxi-mum wetting was determined from the load celldata and divided by the soil volume. The oneday evaporation rate was determined from day 1to day 2 after removing the covers from the col-umns, and then divided by the soil volume. Thelong-term evaporation rate was determinedfrom the slope of the load cell water loss overtime, and was also divided by the soil volume.Compost and no compost treatments were com-pared by analysis of variance considering cycle
as the block. Similar water balance was calcu-lated from near surface hydra probe data.
Water content at given desorption head lev-els were compared between column and coredata by analysis of variance, blocked by col-umn. Saturated hydraulic conductivity (of coresextracted from columns) and infiltration rates(of columns) were log-transformed before sta-tistic analysis. The two treatments (compostversus topsoil) were compared by t-test fortransformed values as well as untransformedbulk density and sub-surface water contents ata given head level of desorption. All differen-ces were considered significant at the p D 0.05level.
RESULTS AND DISCUSSION