Life Sciences Commons^™

Mechanical Aeration And Liquid Dairy Manure: Application Impacts On Grassland Runoff Water Quality And Yield, T. J. Basden, S. B. Shah, J. L. Miller

IGC Proceedings (1997-2023)

Wet weather on heavy soils reduces oxygen availability in the root zone and reduces forage yields. Mechanical aeration can improve forage yield in these soil conditions. Research has shown that under certain conditions, mechanical aeration can increase yield by improving drainage and aeration (Davies et al., 1989); aeration can also increase depression, storage and infiltration thus reducing surface runoff and improving nutrient distribution in the root zone. Aeration on sloping, fertilised grassland can provide environmental (Douglas et al., 1995) and agronomic benefits. The objectives of this study were to evaluate the runoff water quality and agronomic impacts of …

Assessment Of Nitrogen Nutrition Status Of Grasses Under Water Deficit And Recovery, V. G. Dugo, Jean-Louis Durand, F. Gastal

IGC Proceedings (1997-2023)

Grasslands are rarely irrigated. They are therefore systematically submitted to more or less severe water deficits: as well as mineral deficiencies, water scarcity often also results in a reduction of nitrogen (N) status. Although identified some time ago, qualitatively, the interaction with N still remains difficult to take into account in quantitative analyses of crop physiology under water deficits. This paper illustrates how the nitrogen (N) status of the crop changes under water deficits. A N nutrition index (INN) was defined as the ratio of the actual N concentration of forage with the theoretical N concentration under optimal conditions, the …

Nitrogen Mineralisation In Situ And In Controlled Environment, F. Pálmason

IGC Proceedings (1997-2023)

Net mineralisation may be underestimated by in situ soil core methods for at least two reasons: (1) absence of plant N uptake in the soil cores, causing higher immobilisation than in intact soil. Schimel & Bennet (2004) thus concluded that plants compete effectively with microbes, as strongly indicated by cases, where net mineralisation was lower than plant uptake. (2) Gaseous losses of N₂O in closed cylinders can lead to underestimation especially during long incubation periods, Abril et al. (2001) and Vor & Brumme (2002).

The Role Of Grass Tussocks In Maintaining Soil Condition In North East Australia, B. K. Northup, J. R. Brown

IGC Proceedings (1997-2023)

Soils of the grazing lands of north eastern Australia are inherently nutrient-poor. Heterogeneously distributed plants are important to the conservation of the limited amounts of nutrients, through storage in plant tissues or in soil sinks close to plants (Ludwig et al., 1997). Loss of perennial vegetation through disturbance reduces conservation of these resources, to the detriment of feedback mechanisms, and ultimately causes loss of soil condition. Large areas of north east Australia have been degraded, or threatened by degradation, through combinations of variability in precipitation and heavy grazing (Gardener et al., 1990). This study examined the inter-related responses …

Field Experiments To Help Optimise Nitrogen Fixation By Legumes On Organic Farms, A. Joynes, D. J. Hatch, A. Stone, S. Cuttle, G. Goodlass

IGC Proceedings (1997-2023)

During an organic rotation, the aim is to increase the nitrogen (N) content of the soil (and hence build up soil fertility) by recycling crop residues, applying manures/composts and from N fixed by legumes. IGER, with ADAS, Duchy College Cornwall and Abacus Organic Associates are developing improved guidance for organic farmers in the use of fertility-building crops. The main questions are: how to maximise N fixation and how to make the most efficient use of the fixed N? Available soil mineral N, which is generally thought to reduce N fixation, will be increased by manure applications, cutting/mulching and grazing. We …

The Effect Of Forage Legumes On Mineral Nitrogen Content In Soil, M. Isolahti, A. Huuskonen, M. Tuori, Oiva Nissinen, R. Nevalainen

IGC Proceedings (1997-2023)

The cultivation of forage legumes is often suggested as a possibility to improve nitrogen (N) utilisation in farming. However, previous studies have indicated examples in which the cultivation of legumes such as white clover has led to accumulation of large amounts of N in soil (Adams & Pattison, 1985). In this study the potential risks of N leaching were estimated by determining amount of mineral N in the soil.

Cycling Of N And P In Grass-Alone (Brachiaria) And Mixed Grass/Legume (Brachiaria/ Desmodium Ovalifolium) Grazed Pastures In The Atlantic Forest Region Of Brazil, R. M. Boddey, R. Tarré, R. Macedo, C. De P. Rezende, J. M. Pereira, B. J. R. Alves, S. Urquiaga

IGC Proceedings (1997-2023)

There are estimated to be > 80 M ha of Brachiaria pastures in the tropical regions of Brazil. When continuously grazed with only modest fertiliser inputs (and no N) these pastures can maintain reasonable cattle weight gains (> 200 kg LWG/ha per year). However, without fertiliser and when overgrazed, LWGs fall rapidly to low levels. Recent studies have shown that N and P deficiency are the most important factors limiting productivity. The objective of this study was to study fluxes of N and P in the pasture system in order to understand resilience to poor management and minimum nutrient requirements to …

Grassland Productivity And Water Quality: A 21St Century Issue, David M. Nash, P. M. Haygarth

IGC Proceedings (1997-2023)

Key points

1. Irrigation and other changes to the hydrological cycle can increase soil and water salinity.

2. Primary salinisation is a natural process that affects much of Europe, Asia, Africa, the Americas and Australia. Secondary salinisation is caused by human activities such as irrigation and land clearing that mobilise salt stored in the soil.

3. The critical water contaminants exported from grasslands are nitrogen, phosphorus, potential pathogens and sediment.

4. The mechanisms responsible for diffuse pollution from grasslands and mitigation strategies are most effectively investigated using a ‘source-mobilisation-transport’ framework.

5. There is a lack of coherent interaction across discipline …

Elevated Co2 And Extreme Climatic Events Modify Nitrogen Content And Ruminal Protein Digestion Of Temperate Grassland, V. Niderkorn, C. Picon-Cochard

IGC Proceedings (1997-2023)

This study was aimed at analyzing changes in nitrogen (N) content and in vitro protein rumen digestion of an upland grassland exposed to climate changes in controlled conditions. Monoliths of grassland were inserted in 12 macrocosms in which climatic conditions for the 2050s were simulated (i.e., +2.3°C and 33 mm less precipitation compared to the current climatic conditions). Six of them were subjected to ambient CO₂ (390 ppm) while the other six were subjected to elevated CO₂ (520 ppm). After four months, an extreme climatic event (ECE) consisting of four weeks of reducted precipitation (-50%) followed by two …

Effect Of Native Grassland Intensification Over Cattle Performance, N. Caram, F. Casalás, M. Cadenazzi, R. Zanoniani, P. Boggiano

IGC Proceedings (1997-2023)

The objective was to evaluate the effect of different levels of intensification in native grassland over cattle live weight gain (LWG), stocking rate (SR) and average daily gain (ADG) in Uruguay. The study was carried out in 7.8 ha in Paysandú, between winter 2015 and autumn 2019. Experiment was a randomized complete block design, with 4 replicates. The four treatments applied were native grassland (NG), NG overseeded with Trifolium pratense (6 kg.ha^-1) and Lotus tenuis (6 kg.ha^-1) + 40 kg.ha^-1 of P₂O₅ (NGO), NG fertilized with 60 kg.ha^-1 of N + …

Mapping Nitrogen Fixing Shrubs In Dry Unimproved Tussock Grassland, C. C. Boswell, W. L. Lowther, P. D. Espie

IGC Proceedings (1997-2023)

Global Positioning System (GPS) was used to both map the positions of individual nitrogen-fixing shrub plants and record individual plant height and breadth dimensions, within a small catchment of dry sub-humid unimproved short tussock grassland. The distributions of different species of shrubs varied with different landscape units within the catchment. The information will provide the base data for a first approximation of the role of the shrubs in the nitrogen balance of the ecosystem, which is pivotal to the sustainability of pastoral farming in the tussock grasslands.