Vegetation and Soil Characteristics within Over Wintering Areas on Management Intensive Rotational Grazing Farms

A.D. Crowe and A.M. Thompson University of Wisconsin – Madison, Madison, Wisconsin

Introduction

Materials and Methods

Results and Discussion

Conclusions

References

In recent years (1993-2003), grazing herds in Wisconsin have increased in size, and the percentage of Wisconsin dairy farms that practice grazing has increased. As of 2002, one fourth of Wisconsin’s 1,250,000 cows get part of their feed ration from pasture. In 2003, nearly one-fourth of all Wisconsin dairy farms used managed grazing and combined with mixed feed farms, 44 percent of all Wisconsin dairy farms used pasture (Taylor and Foltz, 2006).

In Wisconsin, winter months provide a challenge for farmers who practice grazing. Farmers (grazers and non-grazers) have traditionally kept large numbers of animals in a small sacrifice area for a long period of time during rainy or winter periods. Recently grazers have initiated a practice that keeps livestock rotating through paddocks during the winter months. Regardless of the method (sacrifice or over wintering rotation), manure is deposited on snow or frozen ground, soil is compacted during wet periods (snowmelt and early spring), and soil is eroded due to loss of vegetation cover (Lusby, 1965; Young and Holt, 1977; Clark et al., 2004; Tracy, 2005). Thus, over wintering cattle is an environmental concern. The objective of the study (which was conducted in conjunction with water quality monitoring) was to determine temporal variations in vegetation and soil surface characteristics in managed intensive rotational grazing over wintering areas and to determine whether relationships exist among the measured parameters of leaf area index, available biomass and stem density.

This study was conducted on two Discovery Farms: the Breneman Dairy Farm in central Wisconsin, and the Saxton Homestead Farm LLC in eastern Wisconsin. Research on both farms was initiated in October 2005 on pasture areas used for over wintering the cattle. Breneman Dairy’s over wintering area hosts 70 heifers and dry cows from November until May and the Saxton Homestead Farm’s over wintering area hosts 425 milk cows from early November until Mid-April.

Leaf area index (LAI), available biomass, and stem density measurements were measured in 20 different randomly selected locations in five paddocks that are managed for over wintering cattle (yellow paddocks on Fig. 1 and 2) in October 2005, and May, June, August and September 2006.

Phosphorus and organic matter on the Breneman and Saxon farms were similar in October 2005 and September 2006 (Table 1). The additional paddock outside the over wintering area had consistently lower phosphorus and organic matter levels than the paddocks inside the over wintering area. This may be due to additional feces deposits received during the dormant period on the over wintered area. Available phosphorus and organic matter for both farms was higher than the respective county averages which may be due to soil sampling depths. County averages are based on plow layer soil sampling depth (15 cm) compared to surface sampling depth (top 2 cm) that was used for this study.

In a previous study on the Saxon Homestead Farm, eight composite surface samples (depth unknown) taken outside of the over wintering area near the intermittent stream (Fig. 2) had available phosphorus that ranged from 73-150 ppm with an average of 108 ppm (Johnson, 2000). Available phosphorus may have been lower in this area then in the additional paddock sampled in 2006 because manure spreading and grazing was limited in this area during the winter and spring periods.

Table 2. Relationship between vegetation measurements from Oct. 2005-Sept. 2006.

Clark, J. T. et al. (2004). "Soil surface property and soybean yield response to corn stover grazing." Agronomy Journal 96(5): 1364-1371.Johnson, B. and T. Ward (1997). Evaluating the impacts of intensive rotational grazing on wildlife and water quality on the riparian zone of an intermittent stream in East-Central Wisconsin. Appleton, Fox-Wolf Basin: 1-22. Lusby, G. C. (1965). “Causes of variation in runoff and sediment yield from small drainage basins in western Colorado." Sedimentation Conference, Jackson, Mississippi Proceedings. 14(9): 94-98.Sanderson, M. A. et al. (2001). "Estimating forage mass with a commercial capacitance meter, rising plate meter, and pasture ruler." Agronomy Journal 93(6): 1281-1286.Taylor, J. and J. Foltz (2006). “Grazing in the Dairy State-Pasture use in the Wisconsin Dairy Industry, 1993-2003.” UW-Madison Center for Integrated Agricultural Systems. Ruth McNair, CIAS Publication. Tracy, B. F. (2005). Soil compaction in cropland pastures used for winter grazing. XX International Grassland Congress, The Netherlands, Wageningen Academic Publishers.Young, R. A. and R. F. Holt (1977). "Winter-Applied Manure - Effects on Annual Runoff, Erosion, and Nutrient Movement."

Journal of Soil and Water Conservation 32(5): 219-222.

Soil phosphorus and organic matter content was lower outside the over wintering area than in five paddocks sampled within the over wintering area. Soil samples on both farms were above average county soil test levels, although soil sampling methods were different (surface vs. plow layer). LAI and available biomass had a strong relationship during three sampling events on the Breneman farm and two sampling events on the Saxon farm. LAI and stem density had a strong relationship during two sampling events on the Breneman farm and one event on the Saxon farm. Available biomass and stem density had a strong relationship between two sampling events on the Breneman and Saxon farm. However, strong relationships were not consistent throughout time.

Figure 1. Over wintering watershed and research paddocks on the Breneman Dairy Farm, Columbia Cty, Rio, WI.

Figure 2. Over wintering watershed and research paddocks on the Saxon Homestead Farm, Manitowoc Cty, Cleveland, WI.

Photo 1. Leaf Area Index Photo 2. Rising P late Meter Photo 3. Forage Harvesting

Table 1. Soil phosphorus and OM farm averages from five over wintering paddocks and an additional paddock outside the over wintering area on the Breneman Dairy and Saxon Homestead Farm and average soil test results for Columbia and Manitowoc County (1974-2004 data from the UW Soil & Plant Analysis Laboratory).

The authors are grateful for support from a DATCP-GLCI/UW-CIAS Research Grant, the Breneman Dairy Farm, the Saxon Homestead Farm, Discovery Farms Program, UW College of Agriculture and Life Sciences, and the UW Graduate School.

LAI was measured indirectly using a LAI-2000 Plant Canopy Analyzer (Licor Inc., Nebraska, USA) (Photo 1). Available biomass was estimated using a rising plate meter (Photo 2) along with direct harvesting, at 25% of the sampling locations, to develop a calibration for the meter. Stem densities were estimated by harvesting a 0.04 m2 area (Photo 3) and counting all stems, rhizomes, and tillers in that area.

Surface soil samples (2 cm depth) were collected at each of the vegetation sampling locations in October 2005 and September 2006. Paddock composite samples were analyzed using the total P method with IC-OES. Five sub-paddock composite samples were analyzed for available P using the Bray P1 method and organic matter (OM) using a digestion and weight loss-on-ignition method. An additional paddock on each farm was sampled in September 2006 which does not receive over wintering.

Average LAI on the Breneman Dairy Farm was high (>3) in the fall of 2005 and 2006 and in June 2006 (Fig. 3). The high values of LAI in the fall were most likely due to stockpiling of the forage. The lowest LAI of 0.7 occurred in May 2006. This time was early in the growing season, snow melted during the previous three weeks, and a recent grazing rotation left the forage at a low height. The relatively low LAI of 1.8 in August 2005 was likely a result of recent forage clipping on 4 of the 5 paddocks sampled. On the Saxon Homestead Farm LAI was also high (>3) in the fall of 2005 and 2006 and in August 2006. Stockpiling for winter led to the high fall values. LAI in May was high (2.7) indicating a fast recovery of vegetation after the winter months. The low LAI in June (0.67) was likely due to recent forage clipping in all five paddocks.

Stem density was lowest on both farms in June 2006 (801 and 646 stems/m2 on the Breneman and Saxon farms, respectively) and highest on the Breneman Farm in September (1210 stems/m2) and on the Saxon Homestead Farm in August 2006 (1590 stems/m2) (Fig. 4). Plant growth is expected to slow during the summer and late fall months, with legumes expected to have minimum stem production in late July (Gettle et al., 1996). On the Saxon Homestead a decline in stem density was seen between August and September 2006, and stem density was lower on the Breneman farm during October 2005 than during May 2006. Short grazing rotations in the spring on both farms utilized as much of the spring grass as possible, and may be why a decline in stem density was seen in June 2006.

Individual rising plate meter calibrations for each farm and sampling event were used to estimate available biomass (Fig. 5). R values for the individual calibrations ranged from 0.01-0.74. Poor calibrations can result from uneven ground, trampling, heterogeneity of forage, and observer bias (Sanderson et al., 2001). Available biomass on the Breneman Dairy farm was highest in October 2005 (2394 kg/ha) most likely due to forage stockpiling. May 2006 had the least amount of biomass (805 kg/ha) most likely due to the recent snowmelt and grazing rotation, leaving vegetation little time to recover. August and September had high levels of biomass (1716 and 1508 kg/ha, respectively). On the Saxon Homestead Farm, October 2005 and May 2006 had higher biomass (1884 and 2553 kg/ha, respectively) most likely due to stockpiling, and fast vegetation recovery in the spring. Low biomass in June (790 kg/ha) is attributed to recent forage clipping, and low September estimates were likely due to a poor calibration relationship (R=0.00).

A regression analysis was preformed to determine correlations between LAI and available biomass, LAI and stem density, and available biomass and stem density (Table 2). Strong relationships were found between LAI and available biomass during May (R2=0.55), August (R2=0.97), and September (R2=0.87) 2006 on the Breneman Dairy and during May (R2=0.73) and September (R2=0.48) 2006 on the Saxon Homestead. LAI and stem density were strongly correlated in August (R2=0.45) and September (R2=0.63) 2006 on the Breneman Dairy and May 2006 (R2=0.89) on the Saxon Homestead. Available biomass was strongly related to stem density in October 2005 (R2=0.85) and May 2006 (R2=0.82) on the Breneman Dairy and May (R2=0.87) and June (R2=0.64) on the Saxon Homestead Farm in 2006.

Figure 3. Mean LAI and Standard Deviation on the Breneman and Saxon Homestead farms from October 2005-September 2006.

Figure 4. Mean Stem Density and Standard Deviation on the Breneman and Saxon Homestead farms from October 2005-September 2006.

Figure 5. Mean Available Biomass and Standard Deviation on the Breneman and Saxon Homestead farms from October 2005-September 2006.

Breneman Saxon Breneman Saxon Breneman Saxon

------------------------------------ppm--------------------------------------------------%--------------Oct. 2005 149 252 601 1633 4.1 9.9Sept. 2006 143 266 544 1631 4.1 10.7Sept. 2006-Extra Paddock 91 193 491 909 3.8 5.7Respective County Average 59 41 - - 3.5 3.1

Bray P 1 Total P OM

Breneman Dairy Farm LAI vs Biomass LAI vs Stem Biomass vs StemOctober 2005 0.11 0.1 0.85

May 2006 0.55 0.27 0.82

June 2006 0.05 0.38 0.02

August 2006 0.97 0.45 0.28

September 2006 0.87 0.63 0.27

Saxon Homestead Farm LAI vs Biomass LAI vs Stem Biomass vs StemOctober 2005 0 0 0.06

May 2006 0.73 0.89 0.87

June 2006 0.07 0.07 0.64

August 2006 0.48 0.02 0.15

September 2006 0.01 0.02 0.38