P.M. Haygarth

The impacts of grazing animals on the quality of soils, vegetation, and surface waters in intensively managed grasslands

This chapter provides a comprehensive review of the literature relating to the impacts of grazing animals on the quality of soils, vegetation, and surface waters. It focuses on intensively managed grasslands where there is the greatest potential for these impacts to be observed. The chapter indicates that while well-managed grazing can be beneficial to the environment, intensively managed grazing can actually lead to the degradation of both the soil and vegetation of grassland environments. The various causes, forms, and consequences of this degradation are discussed in detail, and gaps in the knowledge are identified. The chapter highlights the need for recognition and quantification of the relationships between the on-site impacts of grazing animals (i.e., changes in soil properties and vegetation cover) and the off-site impacts of grazing animals (i.e., the impact of these changes on hydrology and water quality in surface waters), as these relationships have, in the past, only been alluded to by authors. However, there exists relatively little research evidence to support and quantify these relationships, thus herein we describe data required to address the lack of understanding of the role of grazing animals on grasslands. Finally, the last section of this chapter considers the land management and remediation options available for the reduction of the impacts of intensive livestock farming.

Assessment of natural fluorescence as a tracer of diffuse agricultural pollution from slurry spreading on intensely-farmed grasslands

The value of natural fluorescence in tracing diffuse pollution, in liquid phase, following slurry application to land was assessed by field experiment using twelve one hectare lysimeters on a heavy clay soil in Devon, UK, during autumn 2007. A strong linear relationship was found between natural fluorescence intensity and slurry concentration. The ratio of indices of tryptophan-like and fulvic/humic-like fluorescence (TI:FI) varied between 2 and 5 for a range of slurries sampled from Devon farms and allowed slurry to be distinguished from uncontaminated drainage waters (TI:FI<1). Incidental losses of slurry, indicated by significantly enhanced TI:FI ratios, high TI and high ammonium levels, occurred via the drain flow pathway of the drained lysimeters during the first small event following slurry-spreading. The maximum estimated loss from a single lysimeter was 2-8kg or 0.004-0.016% of the applied slurry. In the second larger storm event, some five weeks later, significantly enhanced TI:FI ratios in the drain flows were not associated with high TI but with high nitrate levels and, compared to the earlier storm, an increase in the humification index. This implies the loss of slurry decomposition products during this event but further work is needed to validate this. There was no significant enhancement of TI:FI in the surface/throughflow pathways of the drained or undrained lysimeters in either of the events. The observed change over a period of weeks in the strength and nature of the fluorescence signal from spread slurry restricts quantification of slurry losses to those immediately after slurry spreading. Nonetheless, this study demonstrates the utility of fluorescence as an indicator of slurry in drainage waters and the importance of field drains in diffuse agricultural pollution.

Designing Grass Cultivars for Droughts and Floods

Temperate productive grasslands are often located in areas of high rainfall prone to flooding, but even here moderate summer droughts occur with regularity causing significant yield reductions. Grasslands capable of resisting both water excess and deficit are required. Alternative breeding technologies are employed to combine as Festulolium cultivars the desirable traits of Lolium and Festuca species, and also through their enhanced root systems, improve soil structures and hydrology. An amphiploid L. perenne × F. pratensis cultivar can significantly reduce rainfall runoff compared to either its parental species. Evidence suggests this was due to an initial intensive root growth followed by extensive root senescence. This appears to alter soil structure and increase soil porosity and moisture retention providing an ecosystem service by both combating run-off subsequent to heavy rainfall and increasing soil water supply during dry periods.

Dissecting Festulolium chromosome 3 to locate rooting and drought resistance traits

Breeding for drought resistance/tolerance traits that favour continued growth and yield in forage grasses rather than just survival would be of great economic value. Festuca chromosome 3 has proved a rich source of alleles for introgression to enhance the expression of beneficial traits in a Lolium background. Three drought resistant introgression lines and a chromosome 3 recombination series were grown in 1 m deep pipes of compost and drought imposed by withholding water. Root traits were shown to be important in drought resistance and the presence of genes on chromosome 3 with some control over relevant traits has been confirmed. Furthermore it is concluded that Lolium and Festuca should be considered as a single genetic complex of grasses comprising a useful source of variation for breeding.

Heads in the cloud

A professor and several PhD students at MIT examine the challenges and opportunities in human computation.