Belief State Planning for Autonomously Navigating Urban Intersections

Urban intersections represent a complex environment for autonomous vehicles with many sources of uncertainty. The vehicle must plan in a stochastic environment with potentially rapid changes in driver behavior. Providing an efficient strategy to navigate through urban intersections is a difficult task. This paper frames the problem of navigating unsignalized intersections as a partially observable Markov decision process (POMDP) and solves it using a Monte Carlo sampling method. Empirical results in simulation show that the resulting policy outperforms a threshold-based heuristic strategy on several relevant metrics that measure both safety and efficiency.Comment: 6 pages, 6 figures, accepted to IV201

New Cultivars for High Quality, Persistent Legume-Grass Pastures in the Southern USA

In the southern USA one cannot depend on perennial legume-grass pasture systems to have persistently high nutritive quality. \u27Jesup\u27 tall fescue, a cultivar with better persistence in the region than \u27Kentucky 31\u27, was re-infected with a non-ergot alkaloid producing strain of the Neotyphodium coenophialum fungal endophtye (MaxQTM) and found to give persistence equal to Jesup with its endemic strain (E+), but without animal toxins (Bouton et al., 2002). \u27Durana\u27 white clover (Bouton et al., 2004) was developed from regional ecotypes of Trifolium repens f. hollandicum germplasm and found to improve animal performance in both E+ and endophyte-free (E-) versions of Jesup. This experiment aimed to assess the ability of Jesup MaxQ when inter-planted with Durana white clover to provide persistent, high quality pasture in the southern USA

Industry Perspectives, Challenges, and Opportunities to Enhance Alfalfa in Warm Climates

Alfalfa (Medicago sativa L.; aka lucerne) acreage is low in comparison to perennial grasses in warm humid regions. This includes the tropics and subtropics, and in the USA, the Southeastern states. The alfalfa seed industry therefore saw few reasons to target sales and marketing in these regions. This overlooked logical opportunities. In this paper, these opportunities are examined for Southeastern USA. The Southeast contains a majority of beef herd, a high percentage of the dairy herd, and millions of acres suitable for conversion to alfalfa. Alfalfa is also now viewed as the best crop to solve problems inherent with the region’s perennial grass systems. These include interplanting alfalfa to enhance these grasses’ nutritive value and reduce their nitrogen fertilizer costs. Development of grazing tolerant and herbicide resistant varieties extended seasonal production and allowed use as high quality, grazed pasture. Alfalfa is also now used as a rotation crop with corn silage for dairies and an integral component of polyculture mixes for pastures and wildlife plots. Direct marketing and sales efforts by the seed industry needs to substantially increase. Research and extension efforts along with varietal development targeted for warm, humid production systems also needs to continue. This makes regions such as the Southeastern USA an important target to increase alfalfa acreage and seed sales

History of Endophytic Toxicosis and Novel Variety Solutions

Associations of Epichloe endophytes with tall fescue [Lolium arundinaceum (Schreb). Darbush.] and perennial ryegrass (Lolium perenne L.) form the basis for the known science and ecology of mutualistic, fungal endophytes, and especially their impact on livestock. In the USA, millions of acres are endophyte infected today due mainly to planting ‘Kentucky 31’ to reduce soil erosion. Health problems emerged later among animals grazing the grass. These toxicity symptoms were listed under the general term ‘Fescue Toxicosis’. Research demonstrated that ergot alkaloids produced by the mutualism were mainly responsible. Developing endophyte-free versions of major varieties reduced host grass persistence and performance. Farmers seemed stuck with a classic dilemma: animal health or pasture persistence? However, research found that naturally occurring, nontoxic endophyte strains (e.g., “novel”) could be isolated and reinfected into elite grass varieties. Novel varieties restored persistence with none of the toxic alkaloids. The development and commercialization of the first novel endophyte tall fescue variety, Jesup MaxQ, is reported here. Other varieties were developed, and the seed trade now recognizes 3 variety types: toxic, endophyte-free, or novel. However, seed sales of novels are still comparatively low, and The Alliance for Grassland Renewal was formed to advance their use

Alfalfa

Cultivated alfalfa or lucerne (Medicago sativa spp. sativa) is the most important forage legume in the world with approximately 32 million hectares cultivated mainly in the temperate regions of both the northern and southern hemispheres. Intensive research has been conducted on the management and physiology of the crop and a major seed industry has developed world wide. Since insect and disease pests are numerous in alfalfa, development of cultivars with the proper fall dormancy and a broad genetic base for pest resistance has been pursued in order to provide increased adaptation, persistence, and yield. There has been a movement lately to introduce more complex genetic traits into these multiple pest, dormancy specific cultivars. Cultivars with grazing tolerance, potato leafhopper resistance (achieved via introgression of genes for glandular hairs from related Medicago subspecies), and low bloat incidence are now marketed. Continued alfalfa breeding will be necessary to develop resistance to intransigent pests such as Lygus, expand adaption into hostile environments such as saline or acid, aluminum toxic soils, incorporate true bloat resistance, increase N2 fixation, and maximize economic yield. The use of biotechnology methods to improve the crop has already begun. Molecular markers are now being assessed for their practical use in alfalfa breeding. The introduction of novel genes via transformation is also underway in alfalfa. In addition to its role as the major legume hay, silage, and pasture crop, alfalfa is currently being investigated as a fuel for use in generating electricity, a bioremediaton system for removal of harmful nitrates, a source of pulp for paper manufacturing, and a factory for production of industrial enzymes. Finally, alfalfa’s future use as a component in low management mixed pastures, in sustainable conservation agriculture, or as a viable crop in the tropics is beginning to be examined

The Future of Clovers in Forage Systems and as Cover Crops

Clovers (Trifolium spp.) are the most widely used genera of legumes in forage systems, although only a limited number of the hundreds of perennial and annual species are commercially available. The number of varieties available within each of the main commercial species can be high and demonstrates past breeding achievements. Success relates to any clover’s ability to persist in mixtures with other forage species, across a range of soil types, management systems, and climates, while providing animal nutrition and biologically fixed nitrogen benefits. Uses range from traditional pasture mixtures with grasses to inclusion in multi-species mixtures, and as cover crop mixes as part of annual cropping systems. Both conventional breeding and genetic modification will lead to better adapted and performing varieties as well as new traits that provide additional benefits for improved animal nutrition and environmental outcomes. The use of genotyping by sequencing (GBS) to determine genetic variation and population structure for clover improvement programs shows great promise. Selection for improved seed yields while maintaining good agronomic performance will ensure cost effective seed production of commercial varieties. Seed coating with effective rhizobia is paramount for nitrogen fixation benefits to be realised. Management systems research to increase the use and economics of clover varieties in future pasture, cover crop, and carbon farming sustainability systems is critical but challenging