Modeling the regrowth of forage grasses: simulating growth, partitioning, and carbon and nitrogen metabolism.

Reserves play an important role in plants undergoing stress. Plants adapted to defoliation use reserve compounds to regrow leaf area. Modeling grass regrowth should account for these processes. A field experiment was conducted in Gainesville, FL, to study herbage production, partitioning and mobilization of reserve compounds of two tropical grasses (Jiggs bermudagrass and Mulato-2 brachiaria grass), under the combination of two light levels ? 56% and 100% solar radiation, and two N rates ? 30 and 120 kg N ha-1 after each harvest. Herbage mass was quantified at harvest every 28 days.Resumo 379-7

Shade and nitrogen effects on regrowth dynamics, partitioning, and herbage production of Jiggs Bermudagrass and Mulato-2 brachiaria hybrid.

The objectives of this study were to quantify the effects of shade and N fertilization on C and N availability for plant growth, composition of stubble following defoliation, and partitioning of assimilates.Resumo 307-38

Climate Impacts on Agriculture: Implications for Crop Production

Changes in temperature, CO2, and precipitation under the scenarios of climate change for the next 30 yr present a challenge to crop production. This review focuses on the impact of temperature, CO2, and ozone on agronomic crops and the implications for crop production. Understanding these implications for agricultural crops is critical for developing cropping systems resilient to stresses induced by climate change. There is variation among crops in their response to CO2, temperature, and precipitation changes and, with the regional differences in predicted climate, a situation is created in which the responses will be further complicated. For example, the temperature effects on soybean [Glycine max (L.) Merr.] could potentially cause yield reductions of 2.4% in the South but an increase of 1.7% in the Midwest. The frequency of years when temperatures exceed thresholds for damage during critical growth stages is likely to increase for some crops and regions. The increase in CO2 contributes significantly to enhanced plant growth and improved water use efficiency (WUE); however, there may be a downscaling of these positive impacts due to higher temperatures plants will experience during their growth cycle. A challenge is to understand the interactions of the changing climatic parameters because of the interactions among temperature, CO2, and precipitation on plant growth and development and also on the biotic stresses of weeds, insects, and diseases. Agronomists will have to consider the variations in temperature and precipitation as part of the production system if they are to ensure the food security required by an ever increasing population

Effect of changing heart rate on the ocular pulse and dynamic biomechanical behavior of the optic nerve head

Purpose: To study the effect of changing heart rate on the ocular pulse and the dynamic biomechanical behavior of the optic nerve head (ONH) using a comprehensive mathematical model. Methods: In a finite element model of a healthy eye, a biphasic choroid consisted of a solid phase with connective tissues and a fluid phase with blood, and the lamina cribrosa (LC) was viscoelastic as characterized by a stress-relaxation test. We applied arterial pressures at 18 ocular entry sites (posterior ciliary arteries), and venous pressures at four exit sites (vortex veins). In the model, the heart rate was varied from 60 to 120 bpm (increment: 20 bpm). We assessed the ocular pulse amplitude (OPA), pulse volume, ONH deformations, and the dynamic modulus of the LC at different heart rates. Results: With an increasing heart rate, the OPA decreased by 0.04 mm Hg for every 10 bpm increase in heart rate. The ocular pulse volume decreased linearly by 0.13 µL for every 10 bpm increase in heart rate. The storage modulus and the loss modulus of the LC increased by 0.014 and 0.04 MPa, respectively, for every 10 bpm increase in heart rate. Conclusions: In our model, the OPA, pulse volume, and ONH deformations decreased with an increasing heart rate, whereas the LC became stiffer. The effects of blood pressure/heart rate changes on ONH stiffening may be of interest for glaucoma pathology

Using the CROPGRO-peanut model to quantify yield gaps of peanut in the Guinean Savanna Zone of Ghana

Peanut (Arachis hypogaea L.) yield in Ghana is limited by variable rainfall, low soil fertility, pests and diseases, and poor crop management. Field experiments were conducted during the 1997 and 1998 seasons at the Savanna Agricultural Research Station in Ghana to evaluate the CROPGRO-peanut model for its ability to simulate growth, yield, and soil water balance of a peanut crop and to quantify yield losses caused by biotic and abiotic factors. Two peanut cultivars, Chinese which matures in 90 d, and F-Mix which matures in 120 d, were grown rainfed on an Alfisol soil at three sowing dates between May and August in 1997 and at four dates in 1998. Soil water and crop growth were measured during the season and compared with crop model simulations to determine yield-limiting factors relative to potential yield. Growth and yield were highest for the early sowing dates and decreased progressively with later sowing, a trend attributed to leaf diseases. After incorporating functions for percentage leaf defoliation and percentage diseased leaf area, the model accurately simulated soil water content fluctuations, crop growth, and yield of cultivars for the sowing dates and seasons. Simulated yield losses caused by water deficits were small (averaging 5–10%) for early sowing dates (late May to mid-July) and increased with later sowing dates (20 and 70% for third and fourth sowings). Yield losses due to diseases and pests were simulated as a percentage of potential yield under water-limited environments and averaged 40%, also increasing with later sowing dates. Using 13 yr of weather data, simulated yields were reduced 10 to 20% by water deficit for the two earlier (normal) sowing dates, but more for the later sowing dates, while additional yield reductions were attributed to biotic stresses. We conclude that the CROPGRO-peanut model can be successfully used to quantify the yield potential and yield gaps associated with yield-reducing stresses and crop management for this region

Critical perspectives on ‘consumer involvement’ in health research: epistemological dissonance and the know-do gap

Researchers in the area of health and social care (both in Australia and internationally) are encouraged to involve consumers throughout the research process, often on ethical, political and methodological grounds, or simply as ‘good practice’. This paper presents findings from a qualitative study in the UK of researchers’ experiences and views of consumer involvement in health research. Two main themes are presented in the paper. Firstly, we explore the ‘know-do gap’ which relates to the tensions between researchers’ perceptions of the potential benefits of, and their actual practices in relation to, consumer involvement. Secondly, we focus on one of the reasons for this ‘know-do gap’, namely epistemological dissonance. Findings are linked to issues around consumerism in research, lay/professional knowledges, the (re)production of professional and consumer identities and the maintenance of boundaries between consumers and researchers

The future of canine glaucoma therapy

Canine glaucoma is a group of disorders that are generally associated with increased intraocular pressure (IOP) resulting in a characteristic optic neuropathy. Glaucoma is a leading cause of irreversible vision loss in dogs and may be either primary or secondary. Despite the growing spectrum of medical and surgical therapies, there is no cure, and many affected dogs go blind. Often eyes are enucleated because of painfully high, uncontrollable IOP. While progressive vision loss due to primary glaucoma is considered preventable in some humans, this is mostly not true for dogs. There is an urgent need for more effective, affordable treatment options. Because newly developed glaucoma medications are emerging at a very slow rate and may not be effective in dogs, work toward improving surgical options may be the most rewarding approach in the near term. This Viewpoint Article summarizes the discussions and recommended research strategies of both a Think Tank and a Consortium focused on the development of more effective therapies for canine glaucoma; both were organized and funded by the American College of Veterinary Ophthalmologists Vision for Animals Foundation (ACVO‐VAF). The recommendations consist of (a) better understanding of disease mechanisms, (b) early glaucoma diagnosis and disease staging, (c) optimization of IOP‐lowering medical treatment, (d) new surgical therapies to control IOP, and (e) novel treatment strategies, such as gene and stem cell therapies, neuroprotection, and neuroregeneration. In order to address these needs, increases in research funding specifically focused on canine glaucoma are necessary.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/151896/1/vop12678_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/151896/2/vop12678.pd

Productivity and economic feasibility of cultivated forage and food crops in the central highlands of Ethiopia

The study was conducted to evaluate the yield performance of improved forage and food crops and to estimate the profitability of fodder and food crops in Holetta and Ejere areas, central highlands of Ethiopia during 2019 and 2020 cropping seasons. The experiment was laid out in randomized complete block design with three replications and evaluated two annual forage crops, two perennial forage crops, and two cereal food crops. Data on herbage dry matter (DM) yield was collected for forage crops while straw and grain yields were measured for food crops. Partial budget analysis was made to evaluate the economic feasibility of forage and food crops production. The result revealed that the herbage DM yield varied (P<0.05) at each location during each production year and combined over years and between the two locations. The straw and grain yields of food crops also varied (P<0.05) between the two production years and locations. The nutritive values of herbage and straw yields of forage and food crops differed (P<0.05) for all measured parameters. The crude protein and in-vitro dry matter digestibility of perennial forage crops were relatively higher than annual forage crops and straw of food crops. The partial budget analysis result indicated that the gross revenue (GR) and net return (NR) obtained from food crops were the highest followed by annual forage crops while the least was recorded from perennial forage crops during the first year of production. However, perennial forage crops produced the higher GR and NR than food crops and annual forage crops in the second year of production. In the second year of production, among the forage crops, Desho grass generated 308, 293, 287, and 232% while Rhodes grass generated 99, 92, 90, and 62% more NR than wheat, sole oat, barley, and oat/vetch mixtures, respectively. The benefit-cost ratio (BCR) of perennial forage crops was the lowest (3.0 for Desho and 1.6 for Rhodes) in the first year of production but the ratio was the highest (17.2 for Desho and 8.6 for Rhodes) in the second year of production. This confirms the better economic feasibility of perennial forage crops as they can be maintained using minimal management cost once they have been established

Potential benefits of drought and heat tolerance in groundnut for adaptation to climate change in India and West Africa

Climate change is projected to intensify drought and heat stress in groundnut (Arachis hypogaea L.) crop in rainfed regions. This will require developing high yielding groundnut cultivars that are both drought and heat tolerant. The crop growth simulation model for groundnut (CROPGRO-Groundnut model) was used to quantify the potential benefits of incorporating drought and heat tolerance and yield-enhancing traits into the commonly grown cultivar types at two sites each in India (Anantapur and Junagadh) and West Africa (Samanko, Mali and Sadore, Niger). Increasing crop maturity by 10 % increased yields up to 14 % at Anantapur, 19 % at Samanko and sustained the yields at Sadore. However at Junagadh, the current maturity of the cultivar holds well under future climate. Increasing yield potential of the crop by increasing leaf photosynthesis rate, partitioning to pods and seed-filling duration each by 10 % increased pod yield by 9 to 14 % over the baseline yields across the four sites. Under current climates of Anantapur, Junagadh and Sadore, the yield gains were larger by incorporating drought tolerance than heat tolerance. Under climate change the yield gains from incorporating both drought and heat tolerance increased to 13 % at Anantapur, 12 % at Junagadh and 31 % at Sadore. At the Samanko site, the yield gains from drought or heat tolerance were negligible. It is concluded that different combination of traits will be needed to increase and sustain the productivity of groundnut under climate change at the target sites and the CROPGRO-Groundnut model can be used for evaluating such trait