Meat and bone meal (MBM) contains appreciable amounts of nitrogen (N), phosphorus and calcium making it interesting as fertilizer to various crops. The effect of Norwegian MBM as N fertilizer has been evaluated in pot and field experiments. The soils used in the pot experiment were peat and a sand/peat mixture, both low in content of plant nutrients. The field experiment was carried out on a silt loam. In the pot experiment increasing amounts of MBM gave significantly increased yields, although there was a partly N immobilisation shortly after seeding the soil based on peat organic matter. In the field experiment there was no period of N immobilisation and good N effect was found also for small amounts of MBM (Total N 50 kg ha -1 ). At total N 100 kg ha -1 there were no significant differences in grain yield of spring wheat between the treatments with MBM, mineral N fertilizer, and combination of MBM and mineral N fertilizer (N 50 kg ha -1 from each). The results indicate that the relative N efficiency of MBM compared to mineral fertilizer is 80% or higher, if MBM is applied to cereals in spring.

Meat and bone meal (MBM) contains appreciable amounts of total nitrogen ($8%), phosphorus ($5%) and calcium ($10%). It may therefore be a useful fertilizer for various crops. This paper shows results from both pot and field experiments on the N and P effects of MBM. In two field experiments with spring wheat, increasing amounts of MBM (500, 1000, 2000 kg MBM ha À1 ) showed a linear yield increase related to the N-supply. A similar experiment with barley gave positive yield increase for 500 kg MBM ha À1 and no further yield increase for larger amounts of MBM. Supply of extra mineral P gave no yield increase when 500 kg MBM ha À1 or more was applied. Meat and bone meal as P fertilizer was studied in greenhouse experiments using spring barley and rye grass as test crops. N applications were 100 N kg ha À1 to barley and 200 kg N ha À1 to rye grass, either from mineral fertilizer or assuming that 80% of total N in MBM was effective. Four different P deficient soils were given increasing doses of MBM and compared with compound NPK fertilizer 11-5-18, mineral N fertilizer (0 kg P ha À1 ) and a control (0 kg N ha À1 , 0 kg P ha À1 ). In barley there was no significant yield difference between the NPK treatment and MBM treatment with equal N supply, and both had significant higher yield than the treatment receiving the same amount of mineral N without P-supply. The positive yield response of MBM was even larger in rye grass. Both in barley and rye grass a significant residual effect of P from MBM applied the year before was found when the treatments received the same amount of mineral N fertilizer (0 kg P ha À1 ). The pot experiments confirmed the assumed N effect of MBM. When MBM is used according to the N demand of the crops, the P supply will be more than sufficient and residual P will be left in the soil. Since a part of this residual P was utilized by the crops of the following year, it is not recommended to apply P-fertilizer the year after MBM application.

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