Sward Structure Effects on Light Interception in Rotationally-Grazed Orchardgrass (\u3cem\u3eDactylis glomerata\u3c/em\u3e L.)

Grazing managers need to know the relationship of sward height and mass to photosynthetic capacity. The aim of this study was to measure the interception of photosynthetically active radiation (PAR) and relate it to sward structure throughout the grazing season on rotationally-grazed orchardgrass/cocksfoot (Dactylis glomerata L.) pastures

Livestock grazing effects on phosphorus cycling in watersheds

Elevated phosphorus (P) loading of wetlands, streams, lakes, and reservoirs can occur from nonpoint sources such as grazing of uplands, wet meadows, and palustrine wetlands. Erosion caused by livestock grazing or any activity will increase the total P load in streams; however, herbivores can also harvest P from forage and export a significant amount of P from the watershed. Some land managers fail to recognize that the P taken up by plants will continue to cycle through soil and water. Dissolved P or P attached to soil particles suspended in water are the primary vectors of P movement in a watershed. Herbivores add another vector with more opportunities to export P from the watershed. Using best management practices such as rotational grazing, buffer strips next to wetlands, and proper irrigation management should reduce overland flow and streambank erosion. Livestock grazing should harvest and remove a significant amount of P from the ecosystem by incorporation into bone and tissue mass of growing animals and beef export from the basin. The Phosphorus Uptake and Removal from Grazed Ecosystem (PURGE) model uses three separate methods to estimate P retention in cattle, and using limits of the input variables, predicted a range from 4 to 50 Mg P could be removed annually from 17,700 ha of pasture in the Cascade Reservoir watershed in west-central Idaho. With proper grazing management, cattle should be part of a long-term solution to P loading and improvement of water quality in Cascade Reservoir

Daily changes in alfalfa forage quality

Several studies are reviewed which relate the daily variation in total nonstructural carbohydrates (TNC) to hay quality, implications for animal preference studies and hay tests, forage intake by animals, and resulting animal production. From these results we conclude that TNC concentrations in alfalfa can increase linearly during the day. Alfalfa forage samples taken for animal preference or TNC analyses should be taken within lh to control daily variation within 5%. We estimate 136 (first cutting) and 81 lbs TNC/ac (fourth cutting) increase by PM- versus AM-cutting. Increasing windrow width in heavy hay from 48 to 60 in windrow allows for faster dry-down, however in light hay increased windrow width is not necessary. The "super conditioner" may provide faster dry-down of alfalfa hay in some conditions

Harvest management effects on alfalfa quality

To produce dairy quality hay, alfalfa should be cut at an early maturity (pre-bud stage). Harvest management such as the time of day the forage is cut and the rate of hay dry-down can also affect forage quality. Alfalfa accumulates total nonstructural carbohydrates (TNC) during daylight because photosynthesis produces TNC more rapidly than they are exported and utilized for new growth and maintenance. Total nonstructural carbohydrates are composed of starch, fructans, sucrose, glucose, and fructose. Continued plant respiration during darkness depletes 'INC concentration. After hay is cut, plant and microbial respiration will continue to consume TNC until the hay reaches less than about 16% moisture. Therefore it is important to dry the hay as quickly as possible to retain as much INC' as possible, as well as avoiding rain showers and allowing the next crop to grow. New developments in conditioners and forming a wider windrow were evaluated for the effects on hay quality. Our objectives in Study 1 were to: 1) determine daily variation of carbohydrate concentrations and accumulation rates in Alfalfa (Medicago sativa L.), 2) predict a time interval to maximize for TNC levels in hay, and 3) estimate the impact of PM cutting on TNC yield. Study 2 objectives were to evaluate the effects of windrow width and conditioner type on alfalfa hay moisture and forage quality

Animal health problems caused by silicon and other mineral imbalances

Plant growth depends upon C, H, 0, and at least 13 mineral elements. Six of these (N, K, Ca, Mg, P, and S) macro-elements normally occur in plants at concentrations greater than 1,000 mg kg- 1 level. The remaining micro-elements (B, Cl, Cu, Fe, Mn, Mo, and Zn) normally occur in plants at concentrations less than 50 mg kg". Trace amounts of other elements (e.g., Co, Na, Ni, and Si) may be beneficial for plants. Silicon concentrations may range upwards to 50.000 mg kg' in some forage grasses. Mineral elements required by animals include the macro-elements Ca, Cl, K, Mg, N, Na, P, and S; the trace or micro-elements Co, Cu, Fe, I, Mn, Mo, Se, and Zn; and the ultra-trace elements Cr, Li, and Ni. When concentrations of these elements in forages get 'out of whack' their bioavailability to animals may be jeopardized. Interactions of K x Mg x Ca, Ca x P, Se x S, and Cu x Mo x S are briefly mentioned here because more detail will be found in the literature. Limited published information is available on Si, so we have provided more detail. Silicon provides physical support to plants and may reduce susceptibility to pests. However, Si may have negative effects on digestibility and contribute to urinary calculi in animals

Near Infra-Red Measurement of Nonstructural Carbohydrates in Alfalfa Hay

Recently documented benefits from afternoon versus morning cut forage have encouraged laboratory reporting of total nonstructural carbohydrate (TNC) values as part of forage quality testing. Our objective was to determine if infra-red spectroscopy (NIRS), which is being used in many forage testing labs, could be reliably used to quantify forage sugars in hay samples. We used two alfalfa (Medicago sativa L.) sample populations that were analyzed by wet chemistry for sugars and scanned by NIRS. The first set consisted of field-dried hay samples that were oven dried at 70oC and the second consisted of fresh, freeze-dried samples. TNC values were determined more precisely with NIRS than by wet chemistry

Irrigation increases carbon in agricultural soils

Irrigated agriculture sequesters significant amounts of organic C. Irrigation may also sequester significant amounts of inorganic C. Inorganic C reactions are important chemical reactions in irrigated soils and may contribute to the total amount of C sequestered. Calcium content of arid and semi-arid soils tends to be higher than rainfed temperate soils due to calcium rich parent material and low rainfall. Carbonate formation is usually controlled by carbonate equilibrium reactions in the solid and g as phase CO2 . Respiration in plant roots and soil microorganisms continually produce CO, increasing its concentration in the soil atmosphere, modifying carbonate solubility. Since irrigation water flows through a series of canals, where smaller amounts of water are directly exposed to incoming radiation, irrigation water usually has higher temperatures than stream or ground water. Carbon dioxide dissolves in water to form both CO2 as a gas and H2CO3 in solution. Warmer water increases reaction time and, in favourable conditions, precipitates CaCO3 .We measured organic and inorganic C stored in southern Idaho soils having long term land use histories that supported native sagebrush vegetation (NSB), irrigated mouldboard ploughed crops (IMP), irrigated conservation - chisel- tilled crops (ICT) and irrigated pasture systems (IP). Inorganic C and total C (inorganic + organic C) in soil decreased in the order IMP>ICT>IP>NSB. We use our findings to estimate the amount of possible organic, inorganic and total C sequestration if irrigated agriculture were expanded by 10%. If irrigated agricultural land were expanded by 10% worldwide and NSB were converted to IMP, a possible 1.90 x 10' Mg total (organic +inorganic) C (2.72 % of the total C emitted in the next 30 yr) could be sequestered in soil. If irrigated agricultural lands were expanded by 10% worldwide and NSB were converted to ICT, a possible 1.30 x 10' Mg total C (2.24 % of the total C emitted in the next 30 yr) could be sequestered in soil. If irrigated agricultural land were expanded worldwide and NSB were converted to IP a possible gain of 1.7 x 10 8 Mg total C (1.174 % of the total C emitted in the next 30 yr) could be sequestered in soils. Altering land use to produce crops on high output irrigated agriculture, while selected less-productive rainfed agricultural land were returned to temperate forest or native grassland. there could be meaningful reductions in atmospheric CO 2

Irrigation increases inorganic carbon in agricultural soils

Inorganic C reactions are among the most important chemical reactions that occur in irrigated soils and may contribute to the total amount of C sequestered in those soils. Because CO2 can escape from soils to the atmosphere or return to precipitate carbonate minerals, soils are open systems with regard to inorganic C. We measured inorganic and organic C stored in southern Idaho soils having long-term land-use histories that supported native sagebrush vegetation (NSB), irrigated moldboard plowed crops (IMP), irrigated conservation (chisel) tilled crops (ICT), and irrigated pasture systems (IP). Inorganic C and total C (inorganic + organic C) in soil decreased in the order IMP>ICT>IP>NSB. We use our findings to estimate that amount of possible inorganic and total C sequestration if irrigated agriculture were expanded by 10%. If irrigated agricultural land were expanded by 10% worldwide and NSB were converted to IMP, a possible 1.60 x 108 Mg inorganic C (2.78% of the total C emitted in the next 30 years) could be sequestered in soil. If irrigated agricultural land were expanded by 10% worldwide and NSB were converted to ICT, a possible 1.10 x 109 Mg inorganic C (1.87% of the total C emitted in the next 30 years) could be sequestered in soil. If irrigated agricultural land were expanded worldwide and NSB were converted to IP, a possible gain of 2.6 x 108 Mg inorganic C (0.04% of the total C emitted in the next 30 years) could be sequestered in soils. Inorganic C sequestered from land-use changes have little potential to make a significant impact on the concentration of atmospheric CO2. However, when coupled with organic C and altering land use to produce crops on high-output irrigated agriculture while selected less productive rain-fed agricultural land was returned to temperate forest or native grassland, there could be reductions in atmospheric CO2

Management of irrigated agriculture to increase organic carbon storage in soils

Increasing the amount of C in soils may be one method to reduce the concentration of CO2 in the atmosphere. We measured organic C stored in southern Idaho soils having long term cropping histories that supported native sagebrush vegetation (NSB), irrigated moldboard plowed crops (IMP), irrigated conservation-chisel-tilled crops (ICT), and irrigated pasture systems (IP). The CO2 emitted as a result of fertilizer production, farm operations, and CO 2 lost via dissolved carbonate in irrigation water, over a 30-yr period, was included. Net organic C in ecosystems decreased in the order IP > ICT > NSB > IMP. In this study, if NSB were converted to IMP, 0.15 g C m- 2 would be emitted to the atmosphere, but if converted to IP 3.56 g C m 2 could be sequestered. If IMP land were converted to ICT, 0.95 g C m 2 could be sequestered in soil and if converted to IP 3.71 g C m 2 could be sequestered. There are 2.6 x 108 ha of land worldwide presently irrigated. If irrigated agriculture were expanded 10% and the same amount of rainfed land were converted back to native grassland, an increase of 3.4 x 109 Mg C (5.9% of the total C emitted in the next 30 yr) could potentially be sequestered. The total projected release of CO2 is 5.7 X 10'" Mg C worldwide during the next 30 yr. Converting rainfed agriculture back to native vegetation while modestly increasing areas in irrigated agriculture could have a significant impact on CO2 atmospheric concentrations while maintaining or increasing food production