Root and Vigor Response of Big Bluestem to Summer Grazing Strategies

Warm-season grasses e.g., big bluestem (Andropogon gerardii Vitman) are great potential sources of summer forage in eastern Nebraska. Frequent, intensive defoliation can reduce root mass and limit root distribution. Quantifying root structure response to multiple defoliation events in a grazing situation is critical to develop management plans for these types of grasses. This experiment aimed to quantify the cumulative effects of timing and frequency of grazing on root structure and organic reserve estimates in big bluestem pastures

Tillage Effects on Soil Quality Indicators and Nematode Abundance in Loessial Soil under Long- Term No-Till Production

Soil quality indicators and nematode abundance were characterized in a loessial soil under long-term conservation tillage to evaluate the effects of no-till, double-disk, chisel, and moldboard plow treatments. Indicators included soil electrical conductivity (EC), soil texture, soil organic matter (SOM), and total particulate organic matter (tPOM). Nematode abundance was positively correlated with EC, silt content, and total POM and negatively correlated with clay content. Clay content was the main source of variation among soil quality indicators and was negatively correlated with nematode abundance and most indicators. The gain in SOM in the no-till system amounted to 10887 kg over the 24 years or 454 kg ha-1 year-1, about half of this difference (45%) resulting from soil erosion in plowed soils. The balance of gain in SOM with no till (249 kg ha-1 year-1) was due to SOM sequestration with no till. No-till management reduced soil erosion, increased SOM, and enhanced soil physical characteristics

Effects of Summer Grazing Strategies on Organic Reserves and Root Characteristics of Big Bluestem

Quantifying root structure response to multiple defoliation events in a grazing situation is critical in developing management plans for warm-season tall grasses. A pasture experiment was conducted in 1999, 2000, and 2001 near Mead, NE. The objective of the experiment was to determine the effect of timing and frequency of grazing on big blue- stem (Andropogon gerardii Vitman) etiolated tiller growth and root and rhizome structure. Paddocks were grazed at a stocking rate of 9.9 Animal Unit Month (AUM) ha-1 in two to four cycles from mid-May to early-September. In April 2002, five 6.6- 132-cm soil cores were extracted from each paddock. Soil cores were subsampled at 30-cm depth increments for estimates of root mass, root surface area, and root volume. Etiolated tiller tents were used to estimate organic reserves of big bluestem in each paddock in spring 2002. Mean number and weight of etiolated tillers were reduced by up to 40% and 50%, respectively, in paddocks grazed in a sequence of June after internode elongation, early August, and early September. Root structure in the top 30 cm of the soil profile was affected most by multiple defoliation events with \u3c40 d of recovery between grazing periods. Root mass decreased by 25%, while mean surface area and volume of roots declined 10 and 15%, respectively, in the upper 30 cm of the soil profile in paddocks grazed in the sequence of post-internode elongation in June, early- August, and early-September. To maintain vigorous big blue-stem pastures, grazing management should concentrate on the elongation and post-elongation periods. Grazing at the elongation stage should be rotated among paddocks in successive years and the recovery period following grazing at internode elongation should be \u3e40 d