Field studies with radioactive sulphur-labelled gysum fertiliser: IV. Recovery by pasture and soil components

摘要

Abstract In the first year of 2 separate series of field experiments investigating the fate of sulphur (S) applied as radioactive gypsum fertiliser, total mean recovery (soil and pasture) from 8 sites ranged from 30 to 99%. Harvested pasture recovery at each site comprised a small proportion of total recovery and varied from 6 to 33%, depending on stage of pasture improvement, pasture yield, time of fertiliser application, and fertiliser rate. In the absence of re-topdressing in the second year, harvested pasture recovery of S in gypsum fertiliser applied the previous year was in general lower than that in the first year and ranged from 2 to 11%. Over a 2-year period, total recovery of fertiliser S by harvested pasture was 10–40% of the initial application of 45 kg S/ha. The significance of the total recovery values was considered in relation to the effectiveness of fertiliser S applied as gypsum.