Conservation agriculture practice influences soil organic carbon pools in intensive rice-based systems of the Eastern Indo-Gangetic Plain

Studies of rice-based systems in the Indo-Gangetic Plain (IGP) have demonstrated the beneficial effects of Conservation Agriculture on soil organic carbon (SOC) status, along with increased soil health and crop productivity. However, it remains unclear as to the time for such treatments to have a positive effect. In this study of lentil-mung bean-rice and wheat-mung-rice rotations in Bangladesh positive effects of strip planting or bed planting, along with residue return, on SOC pools were apparent after 1.5 years, compared with intensive conventional tillage and limited residue return. Conventional tillage resulted in higher CO₂ emission compared with strip planting or bed planting as did high residue return. In the cereal-dominated rotation, the strip planting system sequestered carbon at a rate of 0.24–0.53 Mg C ha⁻¹ year⁻¹ (at 0–0.15 m depth) while conventional tillage was associated with a carbon loss of 0.52–0.82 Mg C ha⁻¹ year⁻¹. In the legume-dominated rotation, neither practice sequestered SOC. Under strip planting, a minimum annual crop residue input of 1.7 Mg C ha⁻¹ for the cereal-dominated system and 5.2 Mg C ha⁻¹ for the legume-dominated system was required to maintain SOC at equilibrium. We conclude that strip planting with high levels of crop residue return can be an effective and quick strategy in either slowing the loss of SOC or improving C sequestration in the intensive rice-based systems of the Eastern IGP.     

鸡群整齐度的重要性

鸡群的整齐性有益于生产性能这个观点早已得到了大家的公认。为了追求更好的整齐度,营养学家们需要在满足畜禽需要的同时尽可能减少变异、降低安全系数,从而节省饲料成本和提高动物生产性能,尽管在养殖场中提高生产效率的方法不单单减少体重变异这一种。     

Comment on "Carbon-negative biofuels from low-input high-diversity grassland biomass"

Tilman et al. (Reports, 8 December 2006, p. 1598) argued that low-input high-diversity grasslands can provide a substantial proportion of global energy needs. We contend that their conclusions are not substantiated by their experimental protocol. The authors understated the management inputs required to establish prairies, extrapolated globally from site-specific results, and presented potentially misleading energy accounting.     

Assessment of Resting Insulin and Leptin Concentrations and Their Association With Managerial and Innate Factors in Horses

The purpose of this study was to determine how insulin and leptin concentrations varied in a large population of privately owned horses. Further, the study was designed to examine the relationships between insulin and leptin with innate (sex, age, breed) and managerial (diet, exercise) factors in these horses. Resting blood samples (for determination of glucose, insulin, and leptin concentrations), body condition scores, feed information, and health history were collected from 366 privately owned horses. In this group of horses, 48% were considered overweight (Body Condition Score ≥6) and 8% were considered hyperinsulinemic (insulin concentrations >30 μU/mL). Confirming the findings of studies within research herds, both insulin and leptin concentrations were found to be correlated with body condition score (P < .001). It was also found that geldings had higher insulin concentrations than mares (P < .05). Ponies were found to have higher insulin and leptin concentrations as well as higher body condition scores, than several other breeds examined. While not a specific measure of insulin sensitivity, resting insulin concentrations have been associated with quantitative measurements of insulin sensitivity and may be useful in large-scale studies for estimating insulin and glucose dynamics. Because of the association between insulin resistance and obesity with diseases such as laminitis, the findings of the present study may help owners identify horses that may be at risk for the development of such conditions.     

Harvest impacts on soil carbon storage in temperate forests

Forest soil carbon (C) storage is a significant component of the global C cycle, and is important for sustaining forest productivity. Although forest management may have substantial impacts on soil C storage, experimental data from forest harvesting studies have not been synthesized recently. To quantify the effects of harvesting on soil C, and to identify sources of variation in soil C responses to harvest, we used meta-analysis to test a database of 432 soil C response ratios drawn from temperate forest harvest studies around the world. Harvesting reduced soil C by an average of 8 ± 3% (95% CI), although numerous sources of variation mediated this significant, overall effect. In particular, we found that C concentrations and C pool sizes responded differently to harvesting, and forest floors were more likely to lose C than mineral soils. Harvesting caused forest floor C storage to decline by a remarkably consistent 30 ± 6%, but losses were significantly smaller in coniferous/mixed stands (−20%) than hardwoods (−36%). Mineral soils showed no significant, overall change in C storage due to harvest, and variation among mineral soils was best explained by soil taxonomy. Alfisols and Spodosols exhibited no significant changes, and Inceptisols and Ultisols lost mineral soil C (−13% and −7%, respectively). However, these C losses were neither permanent nor unavoidable. Controls on variation within orders were not consistent, but included species composition, time, and sampling depth. Temporal patterns and soil C budgets suggest that forest floor C losses probably have a lesser impact on total soil C storage on Alfisols, Inceptisols, and Ultisols than on Spodosols, which store proportionately large amounts of C in forest floors with long C recovery times (50–70 years). Mineral soil C losses on Inceptisols and Ultisols indicate that these orders are vulnerable to significant harvest-induced changes in total soil C storage, but alternative residue management and site preparation techniques, and the passage of time, may mitigate or negate these losses. Key findings of this analysis, including the dependence of forest floor and mineral soil C storage changes on species composition and soil taxonomic order, suggest that further primary research may make it possible to create predictive maps of forest harvesting effects on soil C storage.     

Timber harvesting alters soil carbon mineralization and microbial community structure in coniferous forests

Timber harvesting influences both above and belowground ecosystem nutrient dynamics. Impact of timber harvesting on soil organic matter (SOM) mineralization and microbial community structure was evaluated in two coniferous forest species, ponderosa pine (Pinus ponderosa) and lodgepole pine (Pinus contorta). Management of ponderosa pine forests, particularly even-aged stand practices, increased the loss of CO₂-C and hence reduced SOM storage potential. Changes in soil microbial community structure were more pronounced in ponderosa pine uneven-aged and heavy harvest stands and in lodgepole pine even-aged stand as compared to their respective unmanaged stands. Harvesting of trees had a negative impact on SOM mineralization and soil microbial community structure in both coniferous forests, potentially reducing coniferous forest C storage potential.     

Complete biceps brachii tenotomy to facilitate internal fixation of supraglenoid tubercle fractures in three horses

OBJECTIVE: To describe a method for internal fixation of supraglenoid tubercle fractures in conjunction with complete tenotomy of the biceps brachii tendon. ANIMALS: Three horses, ranging in age from 8 months to 2 years and weighing from 300 to 400 kg. METHODS: Fractures were repaired by open reduction-internal fixation using bone screws placed in lag fashion and complete tenotomy of the biceps brachii tendon. OUTCOME: All three horses were sound for their intended use with a good cosmetic result 6 months after surgery. CONCLUSIONS: Complete transection of the biceps brachii tendon facilitates supraglenoid tubercle fracture repair by reducing tensile forces exerted on the supraglenoid tubercle. Complete tenotomy does not appear to preclude return to a successful athletic career.