Fertiliser organic manures

N2O contributes to the greenhouse effect with 4% (Schonwiese 1995). N2O emissions from agriculture come from mineral and organic N-fertilisers and from leguminous crops. The emission levels depend on the kind of fertiliser and on the application technique. The N2O emission factors for the most frequently applied forms of mineral N-fertilisers are < 0.5%, for organic manure 1.0 - 1.8% and for N from legumes, about 1% of the fixation rate. 

Soil surface balance measures the differences between the input or application of nutrients entering the soil (e.g. mineral fertilisers or organic manure) and the output or withdrawal of nutrients from harvested and fodder crops. Farm gate balances measure the nutrient input on the basis of the nutrient contents of purchased material (e.g. concentrates, fertilisers, fodder, livestock, biological N-fixation) and farm sales such as meat, milk, fodder, cereals (OECD 1997). 

Conventional arable (synthetic fertiliser), organic arable (green manures) and organic mixed (green manure and manure) over 15 years. 

Available P was adequate but decreased in all except the synthetic fertiliser treatment. The average P budgets (kg P ha y ) were 3.8 for synthetic fertilisers only, -5.0 for synthetic fertilisers and manure, -S.7 for organic and -7.8 for biodynamic (Oehl et al. 2002). 

Less affirmative, though not necessarily less favourable than for conventional systems, is the evidence that has been presented in fields like pollution of water resources and the food chain with pathogens (due to the more pronounced use of organic fertilisers and manure). The same applies to the emission of N2O and CH (because manure stores are seen as a major source and because, on an output unit scale, the CH,j emission potential tends to be higher in organic farming). 

Potassium comes from organic manures and plant debris as well as fertilisers. Within the soil there are three types of potassium water-soluble potassium which is available to plants, exchangeable potassium (an intermediate stage) and a potassium reserve held in the clay lattices within the soil which, by the action of weathering, becomes available over a period of time. 

Comply with the field limit, the Nma (crop nitrogen requirement) limit, closed periods and spreading controls for spreading manufactured nitrogen fertilisers and organic manures. 

At index 2, 40 kg/ha of P and 30 kg/ha of K are required in the seedbed assmning a 3.5t/ha yield. 11kg of extra P and 12kg of extra K will be needed for every torme of yield above 3.5. However, allowance should be made for nutrients applied as organic manures. No nitrogen fertiliser will be required, but a magnesium fertiliser will be required at soil index 0 and 1. 

Less nitrogen is needed in wetter areas, although exactly how much is used wiU depend on the soil nitrogen supply status. More phosphate may be needed on heavier soils, but this will a in depend on the soil phosphate index if the fertiliser is placed 5-10 cm below the seed, the phosphate can be reduced. Potash is important, but savings can be made by using organic manures. As with fodder... 

Crop agronomy and fertiliser inputs will be much the same as for a livestock based unit, except that the absence of any return of organic manures necessitates the substantial use of both nitrogen and potash fertilisers on grass and mainly potash fertiliser on lucerne. In the latter case potash (K O) application can be as much as 375 kg/ha in order to replace that removed by the crop. 

The first fertiliser manual (RB209) with recommendations for agricultural and horticultural crops was published by MAFF in 1973. This manual has been edited several times and is now the industry standard for fertiliser recommendations. Optimum recommended rates have changed according to trial results as well as fertiliser price, use of organic manures and legislation. 

The organic farmer needs all the farmyard manure that his animals produce it is a valuable commodity for maintaining the fertility of his land, it is free and he cannot use most of the faster acting artificial fertilisers. 

In Switzerland, it was found that over a period of 6 years, the capacity of the soil in the plots fertilised with organic cattle manure to supply N to plants was greatly increased compared to soils which had been fertilised with artificial fertilisers (Langmeier, et al., 2000). 

By housing cattle overwinter and composting the farmyard manure, the organic farmer has ready access to a balanced fertiliser that can be spread where most required. The grazing animal does not actually import fertility onto the farm but it does recycle nutrients where it grazes and provides a source of manure when housed. This is as true of sheep, pigs and poultry as of cattle. The only problem with outdoor pigs is that they tend to rip up pastures. 

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