Whole‐Farm Perspectives of Nutrient Flows in Grassland Agriculture

Abstract

who plan row crops and livestock around their grassland hectares are grassland farmers" (Barnes, 1995). Before Grassland agriculture is an important industry for livestock produc-World War II, agriculture in the USA was very diverse tion and land management throughout the world. We review the and integrated, agricultural markets were primarily loprinciples of nutrient cycling in grassland agriculture, discuss examples of grassland farming systems research, and demonstrate the usefulness cal, and nutrients were cycled mainly within farms and of whole-farm simulation for integrating economic and environmental among local farms. With the advent of mechanization, components. Comprehensive studies conducted at the Karkendamm chemical fertilizers, improved seeds, and agrichemicals, experimental farm in northern Germany and the De Marke experifarm size increased, agricultural markets became namental farm in the Netherlands have quantified nutrient flows and tional and international in scope, and nutrient cycles developed innovative strategies to reduce nutrient losses in grassland became more fragmented. Animal agriculture became farming systems. This research has focused on improving the utilizaspecialized and concentrated, relying on off-farm sources tion of manure nutrients on the farm by including grain crops in of feeds and fertilizers, which resulted in nutrient accucropping systems with grassland and by incorporating manure hanmulation on farms. dling techniques that reduce nitrogen losses. Although the information generated in experimental farms is not always directly applicable to Similar changes in farm structure occurred in northother climates and soils, it is being transferred to other regions through western Europe during the 1960s and 1970s (de Wit et computer simulation. A whole-farm model calibrated and verified al., 1987). Farms located in regions with good soils were with the experimental farm data is being used to evaluate and refine converted to crops like winter wheat (Triticum aestivum these strategies for commercial farms in other areas. Simulation of L.), oilseed rape (Brassica napus L.), potato (Solanum farms in northern Europe illustrate that on the sandy soils of this tuberosum L.), and sugarbeet (Beta vulgaris L.), whereas region, maize (Zea mays L.) silage can be used along with grasslands farms on poorer sandy soils specialized in milk producto increase farm profitability while maintaining or reducing nutrient tion with permanent grassland as the main crop. These loss to the environment. Use of cover crops, low emission barns,farms also intensified their use of purchased fertilizers covered manure storages, and direct injection of manure into soil and feed concentrates, and farm-scale nutrient budgets greatly reduces N losses from these farms, but their use creates a net cost to the producer. By integrating experimental farm data with became less balanced because of low conversion rates whole-farm simulation, more sustainable grassland production sys-of nutrients in milk and meat production...

Nitrogen and phosphorus co-limitation and grazing moderate nitrogen impacts on plant growth and nutrient cycling in sand dune grassland

“…However, in this study net nitrification rate was greatest in the un-grazed grassland, supporting an opposing view that grazing by large herbivores can decrease nutrient cycling (van Wijnen et al, 1997;Bakker, 2003;Ford et al, 2013). This may be because cattle distribute N unevenly via their faeces and urine, with pulses of nutrients being patchy in both space and time, whereas smaller mammals such as voles, present within un-grazed units, return nutrients to the soil more uniformly (Rotz et al, 2005). In this study, grazing appeared to result in a de-coupling between N and P cycling.…”

Optimizing nutrient management for farm systems

“…Where animal manures and slurries are present, current advice (and, hopefully, practice) takes much more account of their potential for nutrient supply and also SOM status. Research at Karkendamm experimental farm in Northern Germany and the De Marke experimental farm in the Netherlands quantified nutrient flows and developed management strategies to reduce nutrient losses in grassland farming systems, producing a whole-farm nutrient model that integrated environmental and economic components (Rotz et al 2005). The use of cover crops, low emission barns, covered manure storage and direct injection of manure into soil greatly reduced N losses, but at a net cost to the producer.…”

Farm-scale nitrogen, phosphorus, potassium and sulfur balances and use efficiencies on Australian dairy farms

“…Excess phosphorus (P) on dairy farms can result in soil P increasing beyond agronomic requirements (Weaver and Reed 1998;Mekken et al 2006;Gourley et al 2007), which may also increase the concentration of P in surface runoff (Sharpley 1995), and leachate (Fortune et al 2005). Nitrogen, unlike P is not significantly buffered by soils, and where N is applied in high concentrations such as in dung, urine or fertiliser, losses through volatilisation, denitrification, runoff and leaching can be high (Rotz et al 2005). In addition to offfarm environmental impacts, excessive nutrient accumulation and plant uptake may impact on animal health and production.…”