UTILIZING THE NITROGEN-CONTENT OF ORGANIC MANURES ON FARMS - PROBLEMS AND PRACTICAL SOLUTIONS

Organic manures contain valuable quantities of nitrogen, phosphate and potash, but many farmers regard them as 'waste materials' rather than as sources of plant nutrients. Utilization of the plant-available nitrogen content is poor at present because of manure management practices which lead to leaching and atmospheric losses. Experiments studying the effect of timing suggest that, in order to decrease nitrate leaching, applications of manures which contain much available nitrogen should not be made during the period September to December on freely draining grassland and arable soils. Spring top dressings of dilute pig or cattle slurries and poultry manures to growing cereal crops are generally more efficient than autumn applications, particularly on freely draining soils. Legislation requiring manures to be applied in an environmentally acceptable manner and the economic need for farmers to realize the nutrient value of organic manures are likely to change the farming industry's perception of manures as 'waste materials'.