Revisiting the agronomic benefits of manure: a correct assessment and exploitation of its fertilizer value spares the environment.

The ongoing disintegration of agriculture into specialized farms, specialized regions and even specialized countries, has disrupted local nutrient cycles. This process is promoted and sustained by the use of mineral fertilizers. Ample availability of mineral fertilizers has changed farmers' perception and appreciation of manure. By now, manure is looked upon as 'waste' in some regions. It is a contradiction in terms, however, to regard biological by-products as 'waste'. Apart from this cultural aspect, economical and environmental considerations per se, justify a rehabilitation of manure. First of all a correct assessment of the fertilizer value is required. The present paper explains how to determine the nitrogen fertilizer value (NFV) of manures in a unbiased manner. Subsequently, recommendations are made on how to exploit the potential NFV as good as possible. Undeniably, it is easier to manage mineral fertilizers than manure. However, when proper attention is given to the composition of manure and decisions on rates, timing and placement are made correspondingly, the NFV can be enhanced. This should lead to a drastic reduction of mineral fertilizer use, nutrient surpluses and environmental pollution. Under such conditions, 'manure', 'precision farming' and 'environment' can become reconciled again.