Abstract
Recent years most of the dairy farms have specialized in dairy production only and have been increasing in number of cows per farm to improve their productive efficiency for increasing their profit. However, this often causes the environmental problems such as pollution by livestock waste accumulation in the limited areas.
On the other hand, the material circulation sometimes can be seen in the mixed production area by exchanging livestock manure for wheat straw as bedding material or temporary land exchange between dairy farms and dry field crop farms, and it would reduce the nitrogen load in the area.
In this paper, the influence of the nitrogen load reduction by the material circulation between dairy farms and dry field crop farms was estimated to understand the situation of the nitrogen loads in one town.
Twelve percent of nitrogen (200MgN/year) included in total amount of livestock manure from dairy farms were used for the dry field crops as the result of exchanging livestock manure for bedding materials or temporary land exchange between dairy farms and dry field crop farms. Ninety percent of dry field crop farms growing wheat have supplied the wheat straw to dairy farms for bedding material, and the amount of nitrogen transported from dry field crop farms to dairy farms as the bedding materials containing both wheat straw and bean husk was 25[MgN/year].
Considering the material circulation between dairy farms and dry field crop farms in A town, it was estimated that 180[MgN/year] (40[kgN/ha]) of nitrogen load deceased at dairy farms. This results indicate the regional material circulation is effective to decrease the nitrogen load in the region.
For the future study the influence of the material circulation on nitrogen loads of dry field crop farms needs to be investigated to understand the situation of the nitrogen loads in whole A town.
