Soil nutrient distribution in perennial pastures is likely affected by livestock activities, but detailed spatial patterns on a diversity of farms have not been widely investigated. Livestock management variables, such as placement of drinking water sources, fencing, and winter hay-feeding stations, as well as pasture utilization through seasonal stocking, could affect nutrient distribution despite attempts at uniform application of fertilizers. We sampled perennial pasture portions of three research station farms in North Carolina on a 40 m grid in 2016. Twenty-two soil variables were measured, including routine soil testing of pH, cation exchange capacity, and extractable phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg), as well as nonroutine testing of sand concentration, total and particulate organic carbon (C) and nitrogen (N), and soil-test biological activity. Large statistical variations in nearly all variables occurred within a location. Severely deficient and heavily excessive levels of soil-test P and K were observed on the same farm and sometimes on the same paddock. Soil-test biological activity and total soil N also varied spatially within locations. High nutrient concentrations and soil-test biological activity were congregated in zones of several pastures, which could be related to historical winter hay-feeding and permanent drinking water locations. At the Piedmont location with recent winter hay feeding, both organic and inorganic indicators generally corresponded to the same enrichment zones. At the Coastal Plain location with abandonment of some historical feeding locations, soil-test P remained high near feeding stations, but soil-test K and total soil N became more uniformly distributed due to leaching and/or decomposition dynamics over time. We suggest that both organic and inorganic soil testing indicators should be measured to make nutrient recommendations for better resource utilization. Livestock managers are encouraged to sample pastures in expected zones of nutrient differentiation so that nutrients can be used efficiently and environmental threats can be mitigated.

No abstract

No abstract

Selenium is an important essential nutritional trace element which has been shown to provide protection against certain other metal poisoning. However, it is a suspected carcinogen and teratogen. The uptake, depuration, and toxicity of selenium in Daphnia pulex have been examined. The LC50 at 48 and 96 hr for juvenile animals is 0.6 mg/L and 0.1 mg/L respectively, and for adults it is 1.3 mg/L and 0.5 mg/L respectively. Uptake in adult unfed animals is rapid, reaching a maximum at about 12 hr, but depuration is slow. In fed animals, uptake is slower, reaching a maximum at 96 hr, but initial depuration is followed by a slower prolonged loss. Localization in cells is primarily in the cytoplasmic compartment although evidence is presented which suggests nucleolar localization. Ultrastructural damage is detected by 16 hr after exposure and is initially confined to the mitochondria. Dense deposits accumulate in the mitochondrial matrices. The nature of these deposits is unknown; they may represent a calcium- or phosphate-selenium complex. With time, the mitochondria degenerate. It is clear that relatively low concentrations of selenium are toxic to these aquatic organisms and render them incapable of survival in the natural environment. Concentrations higher than those lethal to Daphnia can be expected, at least in local areas, from the burning or conversion of fossil fuels.

One of the primary goals of extension is to encourage and support adoption of improved technologies. Managed grazing and stockpiling forage are two such technologies. The goal of this project was to encourage adoption of these practices by providing on-farm demonstrations of the technologies. We also collected forage and soil data and held workshops at each of the demonstration sites. Host producers were selected, given a basic kit of temporary fencing supplies for use during the demonstration, and instructed on their proper use during the winter stockpiling season. Forage yield and quality data were collected and soil tests made to show the economic advantages of proper fertilization and grazing fresh forage in contrast to feeding stored forage and concentrate. The nutritive value of the forage stockpiled in September through November (67% total digestible nutrients [TDN] and 14% crude protein, CP) exceeded the needs of the cattle and was greater than the nutrient content of hay present on the farms (59% TDN and 11% CP, P < 0.01). The mean quantity of available forage (2,856 ± 164 kg dry matter per hectare) provided an average of 260 (±81.8) standard cow (545 kg) grazing days per hectare of stockpiled forage. Taking into account the higher nutritive value of the fresh forage when compared with hay and the savings of time and equipment costs by grazing, we estimated that grazing stockpiled forage saved $1.28 per standard cow per day. The grazing management skills gained during this project and the temporary fencing technology were adopted by 93% of the demonstration farms that responded to our follow-up survey (78% of demonstration sites), and the area managed with these technologies increased on these sites more than 350%. Having the hosts share personal experiences played an important role in encouraging their peers to adopt the technologies.