In this paper we describe hillslope‐scale, rainfall‐simulation experiments on karst shrublands dominated by Ashe juniper. These simulations, designed to mimic flood‐producing rainfall events, were carried out at two sites separated by 206 km within the Edwards Plateau of Central Texas. Five hillslope plots were instrumented—two shrub‐covered (canopy) plots and three intercanopy plots measuring 12–14 m in length. We repeated the experiments on the canopy plots after removing the shrubs. For the canopy plots, both before and after shrub removal, 50% or more of the water applied exited the plots as subsurface stormflow and no overland flow occurred. For the intercanopy plots, subsurface stormflow amounted to less than 10% of the water applied and overland flow was between 10 and 50%. These experiments demonstrate the importance of subsurface stormflow in semiarid karst shrublands during flood events, and more generally highlight the fact that subsurface stormflow is important in some semiarid landscapes.

The export of manure sources of P through turfgrass sod grown with manure and as composted manure for Nutrient loading on impaired watersheds can be reduced through turfgrass production on other watersheds are potential export of sod grown with manure and export of composted manure alternatives to subsidized transport of composted mafor turf production on other watersheds. Effects of the sod and manure exports on receiving watersheds were evaluated through monitoring nure to public-works projects (Vietor et al., 2002). The Experimental DesignD.M. Vietor, T.L. Provin, and R.H. White, Soil and Crop Sciences A randomized complete block design comprised three repli-Department, and C.L. Munster, Biological and Agricultural Engications of seven treatments, including controls. Three treatneering Department, Texas A&M University, College Station, TX ments were sod transplanted from Tifway bermudagrass plots 77843.

The Soil and Water Assessment Tool (SWAT) was used to evaluate the influence of woody plants on water budgets of semi‐arid rangelands in karst terrain. The model was configured for the hydrologic evaluation of the North Fork of the Upper Guadalupe River watershed and was calibrated and verified using measured flow data. Nash and Sutcliffe fit efficiencies for daily and monthly verification periods were 0.09 and 0.50, respectively. Streamflow, baseflow, and evapotranspiration (ET) rates were comparable to published field data. Simulated deep recharge was considerably higher than the published values for the Edwards Plateau. The model was then used to simulate conditions with existing brush cover and four different brush removal scenarios. Scenarios were created to represent existing brush and the removal of brush from only locations that were either covered by heavy brush, were on a moderate slope, or were in shallow soils. Resulting data was compared to previous studies of both field experiments and model simulations. Maximum brush removal resulted in a reduction in ET equal to 31.94 mm/yr depth over the entire basin, or 46.62 mm/yr depth over the treated area. Removal of heavy brush cover resulted in the greatest changes in evapotranspiration, surface runoff, base‐flow, and deep recharge. Slope was found to have the greatest effect on lateral subsurface flow.

Municipal programs for turfgrass establishment recommend large volume-based application rates of composted municipal biosolids (CMB). This study compared runoff water quality among combinations of two common turfgrass establishment practices and two CMB sources. Bryan- or Austin-CMB were incorporated into 5 cm of soil at a rate of 12.5 or 25% by volume (v/v) on an 8.5% slope. Tifway bermudagrass [Cynodon dactylon (L.) Pers. x C. transvaalensis Burtt-Davy, var. Tifway] sprigs were planted and established; sod, produced at a separate site using either CMB amendment at the 25% v/v rate, was transplanted to the runoff plots on the same day. A mature stand of bermudagrass was used as a control. Runoff water was collected after each of eight natural rain events during the sampling period. Total runoff water loss (mm) was similar for the CMB-amended sprigged and transplanted sod stands. The concentration of total dissolved P (TDP) in runoff water was greatest from the transplanted sod in the first seven rain events (4.1 to 7.5 mg L(-1)). The concentration of TDP in runoff water was similar at both the 12.5 and 25% v/v incorporation rates. Regression analysis indicated Mehlich-3-extractable soil test P concentrations in soil amended with CMB were positively correlated to concentration and mass loss of dissolved P in runoff. At similar application rates, dissolved P loss in runoff water was reduced by incorporating CMB into the soil on site rather than transplanting sod produced with CMB.

Effects of low-temperature thermal desorption (LTTD) treatment on the ecological properties of soil contaminated by petroleum hydrocarbons were assessed. For this purpose, various ecological properties related to soil health and physicochemical properties of the oil-contaminated soil before and after LTTD treatment were investigated. Total petroleum hydrocarbon concentration, electrical conductivity, organic matter, and total nitrogen decreased while water-holding capacity and available P 2 O 5 increased. The soil color was also changed but textural class was not changed after LTTD. The microbial number and dehydrogenase activity increased following LTTD, but there was no significant difference in the β-glucosidase and acid phosphatase activities. Seed germination succeeded after LTTD, but the germination rate was still lower than that in noncontaminated soil as the growth of plants and earthworms was. The results showed that overall soil health related to biological productivity and environmental functions was improved after LTTD and suggested that LTTD could be a better alternative to other harsh remediation methods. However, ecological indicators still show differences to the adjacent non-contaminated level. Therefore, to ensure safe soil reuse, the change in eco-physiochemical properties as well as contaminant removal efficiency during the remediation process should be considered.

Manure applications can benefit turfgrass production and unused nutrients in manure residues can be exported through sod harvests. Yet, nutrients near the soil surface could be transported in surface runoff. Our research objective was to evaluate responses of bermudagrass [Cynodon dactylon (L.) Pers. var. Guymon] turf and volumes and P and N concentrations of surface runoff after fertilizer or composted manure applications. Three replications of five treatments were established on a Boonville fine sandy loam (fine, smectitic, thermic Vertic Albaqualf) that was excavated to create an 8.5% slope. Manure rates of 50 and 100 kg P ha(-1) at the start of two monitoring periods were compared with P fertilizer rates of 25 and 50 kg ha(-1) and an unfertilized control. Compared with initial soil tests, nitrate concentrations decreased and P concentrations increased after two manure or fertilizer applications and eight rain events over the two monitoring periods. The fertilizer sources of P and N produced 19% more dry weight and 21% larger N concentrations in grass clippings than manure sources. Yet, runoff volumes were similar between manure and fertilizer sources of P. Dissolved P concentration (30 mg L(-1)) in runoff during a rain event 3 d after application of 50 kg P ha(-1) was five times greater for fertilizer than for manure P. Observations during both monitoring periods indicated that total P and N losses in runoff were no greater for composted manure than for fertilizer sources of P at relatively large P rates on a steep slope of turfgrass.

Pyrolysis of crop biomass generates a by-product, biochar, which can be recycled to sustain nutrient and organic C concentrations in biomass production fields. We evaluated effects of biochar rate and application method on soil properties, nutrient balance, biomass production, and water quality. Three replications of eight sorghum [ (L.) Moench] treatments were installed in box lysimeters under greenhouse conditions. Treatments comprised increasing rates (0, 1.5, and 3.0 Mg ha) of topdressed or incorporated biochar supplemented with N fertilizer or N, P, and K fertilizer. Simulated rain was applied at 21 and 34 d after planting, and mass runoff loss of N, P, and K was measured. A mass balance of total N, P, and K was performed after 45 d. Returning 3.0 Mg ha of biochar did not affect sorghum biomass, soil total, or Mehlich-3-extractable nutrients compared to control soil. Yet, biochar contributed to increased concentration of dissolved reactive phosphorus (DRP) and mass loss of total phosphorus (TP) in simulated runoff, especially if topdressed. It was estimated that up to 20% of TP in topdressed biochar was lost in surface runoff after two rain events. Poor recovery of nutrients during pyrolysis and excessive runoff loss of nutrients for topdressed biochar, especially K, resulted in negative nutrient balances. Efforts to conserve nutrients during pyrolysis and incorporation of biochar at rates derived from annual biomass yields will be necessary for biochar use in sustainable energy crop production.

Within semi-arid landscapes, karst areas are among the most productive in terms of water supply-largely because of the high rates of groundwater recharge compared with those of other semi-arid areas. Recharge rates in karst regions may be affected by the type of vegetation cover. Understanding the interactions between recharge and vegetation is important at many levels, but the complex nature of karst hydrology makes this endeavour challenging. This paper presents the results of a set of hillslope-scale rainfall simulation experiments conducted within a juniper-oak woodland and over a shallow karst cave that was instrumented for drip-rate monitoring. The variables measured during these experiments include the amounts and timing of cave recharge, surface runoff, stemflow, and throughfall. The findings of this study provide insights into the importance of canopy interception during runoff-producing events, the nature and relative magnitude of rapid recharge, and the interplay between recharge and surface runoff. Key findings of the study were (1) for simulated rainstorms of around 50 mm, between 0 and 23% of the water applied was intercepted (depending on cloud conditions), and 4-9% of the water reaching the ground surface came from stemflow (which was highest under the wettest conditions); (2) surface runoff accounted for approximately 3% of the water applied; and (3) recharge accounted for between 8 and 17% of the water applied and typically reached its maximum level within 20 min of rainfall cessation, declining rapidly thereafter.