NPS pollutant loads from the soy bean cultivation in the tidal reclaimed uplands as affected by differentfertilizer types

摘要

The Saemangeum tidal reclamation is an ongoing national project to transform tidal area into land by constructing sea dike and developing internal area. Agriculture is one of major land uses being developed but high salinity of tidal soils limits itsuse for flooded paddy cultivation. However, as the grain values increase, introduction of upland crops including barley and soy beans into the land to be developed gained much public attentions and transformed into a major governmental effort. This studywas aimed to investigate the effects of different fertilizer types on nonpoint source pollutant loads when soy bean was grown in the reclaimed uplands. The three fertilization treatments including livestock compost, chemical fertilizer, and no application as control were duplicated in sixplots established at the Kyehwa tideland experimental field of the RDA NICS. The plot size was 5 x 10 m of which water and nutrient balance were monitored to estimate NPS pollutant loads to the surrounding environments. Soil chemical properties were determined on a monthly basis by sampling soils from 30, 50, and 70 cm. Surface runoff water was measured continuously using flumes installed at the outlet of plots. Water samples were also collected from the outlets when rainfall runoff occurred and analyzed for TN and TP concentration determination. Overall surface nitrogen runoff loads were not significantly different among the treatments, while phosphorus runoff from the livestock compost plot was slightly greater than others. Soil nutrient levels of livestock compost plot were higher both in TN and TP than chemical fertilizer plot. The study field soils contain little clay (less than 2%) and their nutrient sorptivities are also low. High organic content of livestock compost may have enhanced soil property in holding nutrient content. The study results are preliminary and further study is needed to confirm statistical significance.