A comparison was made of the overland flow of P between an organic granule fertilizer Duofos (Guano; 22% P2O5) and Triple Superphosphate (38% P2O5) on a seven year-old pasture (Lolium perenne L.) with a gentle slope (1:20) using two ‘drip-type’ rainfall simulators during July 2004 and March 2005. Despite very dry weather conditions during the first half of July 2004 and a major soil moisture deficit, there was significantly lower overland flow in the case of Duofos compared with TSP. An additional very important advantage of Duofos was demonstrated following a 48 hour period of rainfall. Significantly higher concentrations of DRP, acid-hydrolyzable P and total P were recorded in the case of TSP after this rain. Duofos had a much higher organic matter content (86g/kg) compared with TSP (5.6g/kg) which would be expected to reduce P overland flow due to the additional sorption capacity of the organic matter in the granule. The higher concentration of Al and Fe complexes present in Duofos is also expected to have a significant effect on the solubility of P in the formulation. These effects may explain the slow release characteristics of Duofos compared with TSP. This is a key environmental advantage for Duofos especially following rainfall events. There were no significant differences in dry matter yield, soil P concentrations, plant leaf tissue or soil pH between Duofos and TSP at any of the treatment rates under either an intensive nitrogen (250 kg/ha N) or sustainable nitrogen (25 kg/ha N) regime. Duofos may be recommended to reduce P concentrations in overland flow in grassland pastures and may have a particularly important environmental advantage in the period immediately following rainfall or during high rainfall periods.
|Publication status||Unpublished - 2007|
- Nitrogen Fertilizers