Assessment of the risks of nonpoint source pollution of pasture streams related to grazing management

Sediment, phosphorus (P), and fecal pathogens lost from grazed pastures contribute to the non-point source pollution of surface waters. Therefore, the objective of this experiment was to observe the effect of different grazing management techniques on the amount of time cattle spend in or near pasture streams and on the amount of sediment, P, and fecal pathogen loading of into the streams. During the 2008 and 2009 grazing season, a study was conducted at the Iowa State University Rhodes Research and Demonstration Farm utilizing six adjoining 12.1-ha pastures that were bisected by a 141-m reach of stream. The pastures were grouped into two blocks and assigned one of three treatments: continuous stocking with unrestricted stream access (CSU), continuous stocking with stream access restricted to 4.9-m wide stabilized crossings (CSR), or rotational stocking (RS). Pastures were stocked with 15 fall-calving black Angus cows from mid-May to mid-October for 153 days in both years. For two weeks of each month, GPS collars were placed on at least one cow per pasture. For one of the two weeks, alternative off-stream water was made available to cattle in CSU and CSR pastures to determine the effect of off-stream water on cattle distribution. Each month the cattle were stocked on the pastures, bare and fecal-covered ground was measured. Rainfall simulations were conducted in June, August, and October of 2008, April, June, August, and October of 2009, and April of 2010 at six vegetated and six bare locations on the stream banks in CSU and RS pastures and six vegetated locations on the stream banks within the riparian buffer in CSR pastures. In June and August of both years, two cows per pasture were given a bolus of Cr-mordent fiber to determine total and P fecal output. Shedding of the fecal pathogens was measured by collected fresh fecal samples from all 90 cows in June, August, and September of both years. Stream bank erosion was measured by erosion pins at 10 equidistant transects that were measured monthly from May to November. Results show that off-stream water had no effect on cattle distribution. Compared to the CSU treatment, the CSR treatment reduced the probability (P \u3c 0.10) that cattle were within the Riparian Zone (0 to 36 m from stream center) at black globe temperature humidity index (BGTHI) of 50 to 100. Bare ground in and near the stream was generally greater in pastures with the CSU than CSR and RS treatments. Rainfall simulations resulted in greater (P \u3c 0.10) proportions of applied precipitation and amounts of sediment and P transported in runoff from bare than vegetated sites across grazing treatments and from vegetated sites in CSU and RS pastures than vegetated sites in the CSR pastures. The proportion of applied precipitation, sediment and P loading into surface runoff was most closely related to the proportion of bare ground (R2 = 0.5217, 0.4512, 0.4082, respectively). Pathogen shedding of cattle occurred only once throughout the experiment and was never found in precipitation runoff from rainfall simulations. Bovine enterovirus, an indicator virus, was shed by an average of 24.3% of cows over the study and was collected in the runoff of 8.3 and 16.7% of the simulations on bare sites in CSU pastures in June and October of 2008, respectively, and from 8.3% of the simulations on vegetated sites in CSU pastures in April 2009. Stream bank erosion did not differ between treatments. Results of the experiment show that time spent by cattle near pasture streams can be reduced by RS or CSR treatments, thereby, decreasing risks of sediment and nutrient loading of pasture streams even during periods of increased BGTHI. Stream bank erosion via cut banks was the greatest contributor of both sediment and P loading of pasture streams; contributions of sediment and P from surface runoff and grazing animals were considerably less and were minimized by grazing management practices that reduced congregation of cattle by pasture streams

Grazing Management Effects on the Sward and Physical Characteristics Relative to Streams in Cool-Season Grass Pastures

Different grazing management practices in pastures may affect the sward and physical characteristics of riparian areas which affect sediment, phosphorus, and fecal pathogen loading of the pasture streams. To measure these effects, six 30-acre cool-season grass pastures, bisected by a stream, were split into two blocks with three treatments per block. Pastures were grazed by continuous stocking with unrestricted stream access (CSU), continuous stocking with access to the stream restricted to a 16-foot wide stabilized stream crossing (CSR), or rotational stocking (RS). For data and sample collections, pastures were divided into 4 zones: on the streambank (streambanks zone), 0 to 110 feet from the streambanks (110 zone), 110 and 220 feet from the streambank (220 zone), and greater than 220 feet from the streambank (upland zone). Forage heights were measured and forage samples were collected and analyzed for dry matter and mass from areas where cattle did or did not congregate in each zone monthly from May to October. The percentages of bare and fecal-covered ground were also measured monthly at each sampling site. Sward heights were lower in cattle congregation areas than open areas through all months (P \u3c 0.05). In the later months of the grazing season, sward heights and forage mass were less in the streambanks and 110 zones of the CSU pastures than CSR pastures. Pastures with CSU also had higher (P \u3c 0.10) percentages of fecal-covered ground cover in the 110 zone than the other treatments through August. There were few significant differences between treatments for forage sward height, forage mass or bare or fecal-covered ground in the 220 and upland zones in any month

Microclimate Effects on the Temperature/Spatial Distribution of Beef Cows Grazing Cool-Season Grass Pastures by Different Management Practices (A Progress Report)

Congregation of cattle near pasture streams increases fecal cover and decreases forage sward height and mass, thereby, increasing the risks of sediment, nutrients, and fecal pathogens entering the stream and impairing water quality. Restricting access to the streams to stabilized stream crossings or by providing alternative water sources away from the stream may decrease the amount of time that cattle spend near a stream and, thereby, reduce the risk of nonpoint source pollution. Six 30-acre cool-season grass pastures, bisected by a stream, were split into two blocks with three treatments per block. Treatments were: continuous stocking with unrestricted stream access (CSU), continuous stocking with access to the stream restricted to a 16-foot wide stabilized stream crossing (CSR), and rotational stocking (RS). Cattle spent a greater proportion of time in the stream in CSU pastures than other treatments in June (P \u3c 0.05), August (P \u3c 0.05), and September (P \u3c 0.10). During May to July, and in September, cattle in CSU pastures spent a greater (P \u3c 0.05) percentage of time within 110 feet of the stream than in CSR or RS pastures. Offstream water had no effect on cattle distribution near the stream (P \u3e 0.10) in a summer in which there was considerable precipitation resulting in some of natural offstream water sources

Broadcast and Band Phosphorus and Potassium Placement for Corn and Soybean Managed with Till or No Till

No-till minimizes the incorporation of crop residue and fertilizer with soil; resulting in wetter, colder soils and the accumulation of organic matter, phosphorus (P), and potassium (K) near the soil surface. Banding of P and Kcould be more effective than broadcast fertilization by counteracting stratification, applying nutrients in the root zone (starter effect), and minimizing reactions with the soil that may reduce their availability to plants. Therefore, a long-term study was established in 1994 to evaluate P and K fertilizer rates and placement methods for grain yield of corn and soybean managed with no-till and chiselplow/disk tillage

Comparison of Organic and Conventional Crops at the Neely-Kinyon Long-term Agroecological Research Site

The Neely-Kinyon Long-term Agroecological Research (LTAR) site was established in 1998 to study the long-term effects of organic production in Iowa. Treatments at the LTAR site, replicated four times in a completely randomized design, include the following rotations: conventional Corn-Soybean (C-S), organic Corn-Soybean-Oats/Alfalfa (C-SO/A), organic Corn-Soybean-Oats/AlfalfaAlfalfa (C-S-O/A-A) and Corn-SoybeanCorn-Oats/Alfalfa (C-SB-C-O/A). On April 13, 2011, Badger oats were underseeded with BR Goldfinch alfalfa at a rate of 90 lb/acre and 15 lb/acre, respectively. Following harvest of the organic corn plots in 2010, winter rye was no-till drilled at a rate of 75 lb/acre on October 20, 2010

Microclimate Effects on the Temporal/Spatial Distribution of Beef Cows Grazing Cool-Season Grass Pastures by Different Management Practices

Presence of cattle near pasture streams may increase the probability of bare ground and feces on streambanks and increase the risks of sediment, phosphorus, and fecal pathogen loading of water resources through direct deposition or transport in precipitation runoff. Management techniques such as providing off-stream water sources or managing cattle access to pasture streams through rotational stocking or use of stabilized stream access sites may limit the amount of time that the cattle spend near the stream, decreasing the risks of non-point source pollution. Six 30- acre cool-season grass pastures, bisected by a stream, were split into two blocks with three treatments per block. Treatments were: continuous stocking with unrestricted stream access (CSU), continuous stocking with access to the stream restricted to a 16-foot wide stabilized stream crossing (CSR), and rotational stocking (RS). Each pasture was stocked with 15 fall-calving Angus cows. For two weeks in each month from May through September, at least one cow in each pasture was fitted with a GPS collar programmed to record cow position at 10 minute intervals. Off-stream water was made available to cows in pastures with the CSU and CSR treatments for one week of the twoweek position measurement period in each month., Each pasture was divided into four zones to analyze position data; in the stream or on the streambank (stream zone), 0 to 110 feet from the streambank (110 zone), 110 to 220 feet from the streambank (220 zone), and greater than 220 feet from the streambank (upland zone). The combination of the stream and 110 zones were defined as the streamside zone. Cattle in both RS and CSR pastures spent (P \u3c 0.10) less time within the stream and 110 zones than CSU pastures in June and May, and July, respectively. Off-stream water availability had no meaningful effect on cattle distribution in the CSU and CSR pastures. With increasing temperatures, the probability that cattle were present in the streamside zone of CSU pastures increased more rapidly than CSR pastures

Effectiveness of Foliar Fungicides by Timing on Hybrid Corn

Fungicide use on hybrid corn has increased considerably in the past several growing seasons, primarily due to reports of increased yields, even in the absence of disease and higher corn prices. A number of fungicides are registered for use on corn. The objectives of this project were to 1) assess the effect of timing of application of fungicides on standability, 2) evaluate the yield response of hybrid corn to foliar fungicide application, and 3) to discern differences, if any, between fungicide products

Grazing Management Effects on Sediment, Phosphorus, and Pathogen Loading of Streams in Cool-Season Grass Pastures

Erosion and runoff from pastures may lead to degradation of surface water. A 2-yr grazing study was conducted to quantify the effects of grazing management on sediment, phosphorus (P), and pathogen loading of streams in cool-season grass pastures. Six adjoining 12.1-ha pastures bisected by a stream in central Iowa were divided into three treatments: continuous stocking with unrestricted stream access (CSU), continuous stocking with restricted stream access (CSR), and rotational stocking (RS). Rainfall simulations on stream banks resulted in greater (P \u3c 0.10) proportions of applied precipitation and amounts of sediment and P transported in runoff from bare sites than from vegetated sites across grazing treatments. Similar differences were observed comparing vegetated sites in CSU and RS pastures with vegetated sites in CSR pastures. Bovine enterovirus was shed by an average of 24.3% of cows during the study period and was collected in the runoff of 8.3 and 16.7% of runoff simulations on bare sites in CSU pastures in June and October of 2008, respectively, and from 8.3% of runoff simulations on vegetated sites in CSU pastures in April 2009. Fecal pathogens (bovine coronavirus [BCV], bovine rotavirus group A, andEscherichia coli O157:H7) shed or detected in runoff were almost nonexistent; only BCV was detected in feces of one cow in August of 2008. Erosion of cut-banks was the greatest contributor of sediment and P loading to the stream; contributions from surface runoff and grazing animals were considerably less and were minimized by grazing management practices that reduced congregation of cattle by pasture streams

Grazing Management Effects on Sediment, Phosphorus, and Pathogen Loading of Pasture Streams

In order to quantify the sources of sediment, phosphorus (P), and pathogen loading of pasture streams, six 30-acre pastures, bisected by a stream, were stocked with 15 fall-calving cows from mid-May through midOctober of two years by continuous stocking with unrestricted stream access (CSU), continuous stocking with stream access restricted to 16-foot wide stabilized crossings (CSR), or rotational stocking (RS). Cows in RS pastures excreted less fecal P than cows in the CSU and CSR pastures. The proportion of water applied and the amounts of sediment and P in precipitation runoff during rainfall simulations were greater from bare sites on the stream banks of CSU or RS pastures than vegetated sites of CSU, RS, or CSR pastures. Amounts of stream bank erosion did not differ between grazing management treatments. When sources of sediment and P were compared, stream bank erosion contributed 99.5 and 94.4% of the sediment and P loading of the stream. At the stocking rate used in this experiment, direct fecal deposition in the pasture stream contributed more P than transport in precipitation runoff. The incidence of fecal pathogens E. coli O157:H7, bovine coronavirus, and bovine rotavirus shedding in the feces of the cows in this experiment as well as in the runoff from the rainfall simulations was extremely low. These results suggest that the major source of sediment and P loading of pasture streams is stream bank erosion primarily associated with stream hydrology. Grazing management practices that reduce congregation of grazing cattle near pasture streams will reduce sediment and nutrient loading resulting from direct fecal deposition or transport in precipitation runoff. While fecal pathogens may be potential pollutants of pasture streams, pathogen loading of pasture streams by grazing cattle is infrequent and dependent upon the pathogen shedding, temporal\spatial distribution of grazing cattle, and surface runoff from stream banks, in respective order

Assessment of the risks of nonpoint source pollution of pasture streams related to grazing management

Sediment, phosphorus (P), and fecal pathogens lost from grazed pastures contribute to the non-point source pollution of surface waters. Therefore, the objective of this experiment was to observe the effect of different grazing management techniques on the amount of time cattle spend in or near pasture streams and on the amount of sediment, P, and fecal pathogen loading of into the streams. During the 2008 and 2009 grazing season, a study was conducted at the Iowa State University Rhodes Research and Demonstration Farm utilizing six adjoining 12.1-ha pastures that were bisected by a 141-m reach of stream. The pastures were grouped into two blocks and assigned one of three treatments: continuous stocking with unrestricted stream access (CSU), continuous stocking with stream access restricted to 4.9-m wide stabilized crossings (CSR), or rotational stocking (RS). Pastures were stocked with 15 fall-calving black Angus cows from mid-May to mid-October for 153 days in both years. For two weeks of each month, GPS collars were placed on at least one cow per pasture. For one of the two weeks, alternative off-stream water was made available to cattle in CSU and CSR pastures to determine the effect of off-stream water on cattle distribution. Each month the cattle were stocked on the pastures, bare and fecal-covered ground was measured. Rainfall simulations were conducted in June, August, and October of 2008, April, June, August, and October of 2009, and April of 2010 at six vegetated and six bare locations on the stream banks in CSU and RS pastures and six vegetated locations on the stream banks within the riparian buffer in CSR pastures. In June and August of both years, two cows per pasture were given a bolus of Cr-mordent fiber to determine total and P fecal output. Shedding of the fecal pathogens was measured by collected fresh fecal samples from all 90 cows in June, August, and September of both years. Stream bank erosion was measured by erosion pins at 10 equidistant transects that were measured monthly from May to November. Results show that off-stream water had no effect on cattle distribution. Compared to the CSU treatment, the CSR treatment reduced the probability (P < 0.10) that cattle were within the Riparian Zone (0 to 36 m from stream center) at black globe temperature humidity index (BGTHI) of 50 to 100. Bare ground in and near the stream was generally greater in pastures with the CSU than CSR and RS treatments. Rainfall simulations resulted in greater (P < 0.10) proportions of applied precipitation and amounts of sediment and P transported in runoff from bare than vegetated sites across grazing treatments and from vegetated sites in CSU and RS pastures than vegetated sites in the CSR pastures. The proportion of applied precipitation, sediment and P loading into surface runoff was most closely related to the proportion of bare ground (R2 = 0.5217, 0.4512, 0.4082, respectively). Pathogen shedding of cattle occurred only once throughout the experiment and was never found in precipitation runoff from rainfall simulations. Bovine enterovirus, an indicator virus, was shed by an average of 24.3% of cows over the study and was collected in the runoff of 8.3 and 16.7% of the simulations on bare sites in CSU pastures in June and October of 2008, respectively, and from 8.3% of the simulations on vegetated sites in CSU pastures in April 2009. Stream bank erosion did not differ between treatments. Results of the experiment show that time spent by cattle near pasture streams can be reduced by RS or CSR treatments, thereby, decreasing risks of sediment and nutrient loading of pasture streams even during periods of increased BGTHI. Stream bank erosion via cut banks was the greatest contributor of both sediment and P loading of pasture streams; contributions of sediment and P from surface runoff and grazing animals were considerably less and were minimized by grazing management practices that reduced congregation of cattle by pasture streams.</p