Mark L. McFarland

Improving conservation practices programming to protect water quality in agricultural watersheds: Lessons learned from the National Institute of Food and Agriculture-Conservation Effects Assessment Project

Nutrient enrichment and sedimentation of water resources is a significant problem in the United States and globally (Carpenter et al. 2011; Dubrovsky et al. 2010; Hilton et al. 2006). Specifically, in the United States, over 6,908 water bodies are listed as being nutrient impaired and 6,165 are sediment impaired (USEPA 2012). Agricultural nonpoint source pollution contributes, in part, to impaired water resources in many of these watersheds (NRC 2008; USEPA 2010). Conservation practices, including conservation tillage, nutrient management, and riparian buffers, are routinely used to reduce off-site losses of sediment, nutrients, pesticides, and bacteria from agricultural operations. Many research studies, generally conducted at the plot- or field-scale, report ranges in effectiveness of such conservation practices, from being negative to 100% effective (Gagnon et al. 2004; Gagnon et al. 2008; Jokela et al. 2004; Line et al. 2001; Richards and Baker 2002; Schnepf and Cox 2006; Sharpley et al. 2006; Shepard 2005; Smith et al. 2006). Documentation of combined practice impacts on water quality at the watershed scale has been more difficult than in plot or field-scale studies. The Black Creek Project in northeastern Indiana and the Model Implementation Program (MIP) promoted by the USDA and US Environmental Protection Agency (USEPA)…

Effects of tillage and cropping sequence on soil physical properties.

Abstract The interactive effects of cropping sequence and tillage on soil physical properties are poorly documented. This type of information is essential if maximum efficiency is to be obtained from various farming systems. Field evaluations were conducted on a Ships clay (Udic Chromustert) — Weswood silt loam (Fluventic Ustochrept) intergrade in Burleson County, TX to determine the effects of three cropping sequences (continuous soybean ( Glycine max (L.) Merr.), wheat ( Triticum aestivum L.) - soybean doublecrop, and sorghum ( Sorghum bicolor (L.) Moench)-wheat-soybean rotation) and two tillage methods (conventional disk tillage and no tillage) on soil bulk density, soil strength, and microaggregation. Tillage did not significantly influence soil bulk density or soil strength after 3 years. Conventional tillage significantly decreased microaggregation compared with no tillage at 0–76 mm after 3 years and at 0–152 mm after 6 years. Differences, however, were less dramatic in the sorghum-wheat-soybean cropping sequence as compared with the other sequences studied. Significant interactive effects were observed for cropping sequence × depth on soil bulk density, cropping sequence × tillage and cropping sequence × location (furrow vs. bed) on soil strength, and cropping sequence × tillage on microaggregation.

Selective-placement burial of drilling fluids: effects on soil properties, buffalograss and fourwing saltbush after 4 years.

A field study was established in 1986 to evaluate selective-placement burial as an alternative technique for on-site disposal of drilling fluids in arid and semiarid areas. Soluble salt and heavy metal migration in the soil, and establishment, yield and chemical composition of fourwing saltbush (Atriplex canescens (Pursh) Nutt.) and buffalograss (Buchloe dactyloides (Nutt.) Engelm.) were determined 44 months after simulated reserve pits were constructed to provide burial depths of 30, 90 (with and without a 30-cm thick, coarse limestone capillary barrier), and 150 cm, with sequential replacement of stockpiled subsoil and topsoil. Soluble salt concentrations increased most significantly in the 30-cm zone immediately above buried drilling fluids, regardless of treatment. Upward salt movement was greatest in the 90- and 150-cm treatments, with significant increases in Electrical Conductivity (EC) and Exchangeable Sodium Percentage (ESP) values observed as much as 60 and 30 cm above buried drilling fluid, respectively. Capillary barriers reduced the extent of upward salt migration, but had little effect in soil zones immediately overlying the drilling fluid. There was no evidence of upward migration of Ba, Cr, Cu, Ni, or Zn from buried drilling fluids into overlying soil, but concentrations of Cu and Zn were greater in saltbush stems grown on plots with buried drilling fluids on 1 site. Fourwing saltbush survival averaged 92 to 100% and was not affected by depth of drilling fluid burial. Significant reductions in saltbush canopy cover and yield on the 30-cm burial treatment were observed on 1 study site. Elevated Na concentrations in aboveground tissue of both species in the 30-cm burial treatment on 1 site did not adversely affect survival or plant growth. Differences between study sites in the extent of upward salt movement in the soil and in plant response were attributed to differences in soil clay type and content.

Efficacy of Using Dairy Manure Compost as Erosion Control and Revegetation Material.

In a simulated rainfall study, first flush (one liter) and the remaining runoff samples were collected from 12 non-vegetated and isolated field plots established on a 3:1 embankment constructed as a road right-ofway. These plots were assigned to four treatments namely compost manufactured topsoil (CMT); 2.5 cm of dairy manure compost (DMC) incorporated into 8-cm of topsoil, erosion control blanket (ECC); a 5-cm layer of DMC and woodchips blended (2.5 cm each mixed by volume) and applied on top of the undisturbed soil, agronomic rate compost (ARC); DMC broadcast at 39.5 t/ha, and commercial fertilizer (CF); broadcast at the rate of 112kg N /ha, 49 kg P /ha, and 83 kg K /ha, respectively. The ECC plots had smaller total runoff mass than all other treatments and significantly lower TS and TSS in the runoff as compared to those in the runoff from CF plots. Overall, plots amended with DMC or DMC/woodchips blend, though much higher in N, P and K, produced less runoff and sediment and nutrients in the runoff as compared to the mineral fertilizer plots without any organic amendment. It was concluded that ECC and CMT treatments established to control erosion and revegetate, respectively, a newly constructed road-right-of-way and shortly there after, subjected to rain (a worst case scenario) will be effective in erosion control. Even though compared to the CF treatment, generally smaller quantities of N, P and K were measured in the runoff from ECC and CMT treatment plots, N and P concentrations in the runoff were high from the standpoint of water quality.

Residual soil nitrogen credits for corn production along the upper Texas Gulf Coast region

ABSTRACT Studies were conducted to evaluate response of dryland corn (Zea mays L.) along the upper Texas Gulf Coast to residual soil nitrate-nitrogen (NO3-N) measured to depths of 15, 30, and 61 cm. Residual soil NO3-N levels ranged from 3.4 to 31.6, 7.8 to 49.3, and 9.0 to 71.7 kg ha−1, respectively, in 0 to 15, 15 to 30, and 30 to 61 cm depth increments, with cumulative NO3-N ranging from 23.5 to 114.5 kg ha−1 across sites-years. Where N fertilizer was reduced due to N crediting, yields and bushel weights at all 13 site-years showed no difference from those receiving full recommended N rates. A yield response to any level of added fertilizer N above the control was observed for only 6 of 13 site-years. These results indicate a high potential for success in crediting carryover soil NO3-N to 61 cm as a means of reducing applied nitrogen fertilizer rates.